A structured approach to allergen avoidance in dwellings, withspecial emphasis on the ecosystem of humid indoor walls androom partitionsCitation for published version (APA):Kort, H. S. M. (1994). A structured approach to allergen avoidance in dwellings, with special emphasis on theecosystem of humid indoor walls and room partitions. Technische Universiteit Eindhoven.https://doi.org/10.6100/IR426296

DOI:10.6100/IR426296

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Helianthe Kort

\

A STRUCTURED APPROACH TO ALLERGEN AVOIDANCE IN DWELLINGS

WITH SPECIAL EMPHASIS 01\1

THE ECOSYSTEM OF HUMID INDOOR WALLS AND ROOM PARTITIONS

Cover: Tape-imprint taken from a humid room partition in Doorn (the Netherlands) showing an acarid mite surrounded by an Aspergillus fungus (magnification: approximately 1000 x; photograph taken by H. Vas)

CIP-GEGEVENS KONINKLIJKE BIBLIOTHEEK, DEN HAAG

Kart, Helianthe Sherida Marianne

A structured approach to allergen avoidance in dwellings, with special emphasis on the ecosystem of humid indoor walls and room partitions I Helianthe Sherida Marianne Kort Proefschrift Technische Univerisiteit Eindhoven, 1994 - met een samenvatting in het Nederlands

ISBN 90-386-0314-2

Trefw.: mijten; woningen I allergie; preventie.

Printed by Elinkwijk BV, Utrecht

A STRUCTURED APPROACH TO ALLERGEN AVOIDANCE IN DWELLINGS,

WITH SPECIAL EMPHASIS ON

THE ECOSYSTEM OF HUMID INDOOR WALLS AND ROOM PARTITIONS

PROEFSCHRIFT

ter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de Rector Magnificus, prof.dr. J.H. van Lint, voor

een commissie aangewezen door het College van Dekanen in het openbaar te verdedigen op

woensdag 30 november 1994 om 16.00 uur

door

HELIANTHE SHERIDA MARIANNE KORT

geboren op 23 juli 1962

Paramaribo, Suriname

Dit proefschrift is goedgekeurd door de promotoren prof.dr. J.E.M.H. van Bronswijk en prof.ir. J. Vorenkamp

The research pertaining to this thesis was financed by the Stichting Minibiolo­gisch Onderzoek (SMO) in Rotterdam, the Netherlands.

All the way round and back again (Charles lves 1874 1954)

Ter nagedachtenis van mijn vader Aan mijn moeder

Aan Lucien en Felicien

TABLE OF CONTENTS

CHAPTER 1: INTRODUCTION

CHAPTER II: ECOLOGICAL RELATIONSHIPS

11.1: Laboratory Studies

11.1.1 Organic soiling and mould growth on indoor surfaces

11.1.2 Mould-devouring mites differ in guanine excretion from dust-eating acari, a possible error source in mite allergen exposure studies

11.1.3 Four-year stability of Der p I in house dust under simulated domestic conditions in vitro

11.2: Home studies

11.2.1 Moulds, mites and moisture, a preliminary report on six cases of fungal damage in dwellings

11.2.2 Mites, Dust Lice, Fungi and their interrelations on damp walls and room partitions

11.2.3 Allergenic mites on mineral walls and in textiles

CHAPTER Ill: HEALTH DAMAGE

Ill. 1 Vorratsmilbenforschung aus allergologischer Sicht

111.2 Clinical improvement after unusual avoidance measures in the home of an atopic dermatitis patient, a case report

111.3 Clinical and technical efficacy of mite avoidance measures in 3 atopic dermatitis cases

1

13

21

29

35

43

51

57

69

75

CHAPTER IV: GENERAL DISCUSSION & SUMMARIES

IV.1 General discussion

IV.2 Summary

IV.3 Samenvatting

CURRICULUM VITAE

89

103

109

115

CHAPTER I INTRODUCTION

2

INTRODUCTION

We consider our houses as safe and secure structures, giving protection from noxious outdoor environmental factors. In the Netherlands more than 70% of clock hours is spent indoors [36]. We hardly realize that indoor environmental factors in our homes can be a greater threat to our well-being than outdoor influences. We discriminate between chemical, physical and biological indoor effectors. Radon, a physical factor evaporating from brick, concrete and gypsum plaster, may cause problems with the respiratory system such as asthma, or cancer [2;36;41]. Formaldehyde, a chemical substance, evaporates from chip-board, floor coverings, or insulation material in dwellings and may elicit headaches, nausea and allergic diseases, such as asthma and rhinitis [36;40]. Cigarette smoke is by far the best known chemical irritant to damage our health indoors [36].

Biological agents, such as moulds, mites and insects, attack building and furnishing materials and health, causing economical damage. These organisms are highly dependent on the availability of water. Humidity and water-vapour permeability influence water availability on the surfaces of finishing and furnishing materials [1; 19]. Humidity and water-vapour permeability may also directly increase the adverse effects of chemical agents such as formaldehyde [40].

Dwellings, moulds and mites

Mould genera found on wall paper and paint include: Alternaria, Cladosporium, Penicillium, Phoma, Aspergillus, Aureobasidium, and Mucor [10].

Fungi may be arranged according to the water activity (Aw "'R.H.{%) I 1 00) requirements in their niches. In xerophilic species such as Aspergillus herbariorum, growth occurs at relative humidities as low as 65 to 75% (RH). Mesophyllic species including Cladosporium herbarum, Penicillium chrysogen-

, um, Aureobasidium and, Merulius lacrymans will flourish starting from 80% RH. Hydrophillic species to which Mucor racemosus, Phoma and Alternaria species may be counted, only thrive above 85% RH [44].

For moulds, indoor materials offer a broad choice in carbon or nitrogen sources including cellulose in wall paper and some paints, acetate in glues and acrylate, and casein in floor and wall equalizer formulations. Soiling of indoor materials, floor, walls, and ceilings by house dust or greasy dirt constitutes an additional nutritional substrate. Under stress conditions, for instance when food is limited, moulds are able to alter their environment by the excretion of protons or sequestration of toxins noxious to their fellow home inhabitants [31 J.

Other factors that play a role in mould growth in dwellings include: relative humidity and temperature. The relative humidity and not the tempera­ture is a limiting factor for mould growth. Temperature is a factor of minor importance, since on most surfaces it ranges between 10 - 30 • C [9]. This whole range is appropriate for mould development.

Changes in Aw of only 0.02 may determine whether mould spores germi­nate or not. In some species, it also determines the development of the sexual or the asexual state [46]. Furthermore, Grant et al. have shown that with increasing temperature and nutrition quality, a reduction in minimal Aw require­ments of moulds is seen [27].

20% Of the housing stock in the Netherlands and 15% in England proved

3

to have problems with dampness and moulds [15;53]. In humid dwellings, with a relative humidity above 85% wood-decaying fungi such as, Merulius /acrymans, break down wooden floors and are able to penetrate mortar joints while spreading to other timber.

Faults in building design or construction (heat-bridges or limited ventila­tion) result in problems with dampness and moulds. Energy conservation efforts started in the seventies have led to sealed houses. Dwellings are not only insulated against heat loss, but ventilation effectivity is also diminished [30]. Humidity spots develop on walls, together with mould growth. People are not triggered to ventilate their houses at high moisture production, since double glass prevents visible surface condensation on the window. Condensation will then occur on or in lesser-insulated walls, floors and ceilings. Damage patterns, caused by fungal growth, often give a clue as to the prevailing type of humid­ity; whether the damage is caused by high indoor relative humidity or by condensation [26].

Damage due to mould growth may range from a mouldy smell, discolour­ing or destruction of the surface of finishing layers or furnishings. All this leads to inconvenience for the tenants: restriction in residential pleasure. Fungal defacement of interior finishes is the subject of another thesis at Eindhoven University of Technology [1]. In contrast, in this thesis the medical conse­quences and their biological and building technological background are focal points.

At least 141 mite species have been isolated from house dust but the five most frequent mite taxa in houses are: Pyroglyphidae, Glycyphagidae, Acaridae, Oribatids and Cheyletidae [9].

House dust mites live in dust-rich environments such as beds, carpets and upholstery where they have plenty of food in the form of skin scales. The house dust ecosystem, in which house dust mites play an important role was first described by van Bronswijk [7].

Mites share the house dust niche with fungi, such as Aspergillus pencil/aides. These xerophilic fungi are of nutritional value to pyroglyphid mites [8;23;39]. The sharing of a niche is also seen in granaries with storage mites and storage fungi [51].

Parallel with the situation in moulds, temperature is a factor of minor importance. Relative humidity is limited for the development of pyroglyphid mites. In our houses, nutrition is not limiting for pyroglyphids. A person loses 1 to 2 grams of skin scales a day [12]. The abundance of pyroglyphid mites is positively correlated with the dampness in the houses [56]. In the Netherlands 70% of the housing units have an indoor air humidity of more than 8.5 g water/ m3

, the limit between the Dutch indoor climate classes II and Ill when assessed in the heating season. These coincide with a harmful mite-concentration of 10 mites per g floor dust [52].

Storage mites thrive better in mouldy surroundings. This does not mean that visible mould growth has to be present. Fine fungal mycelia, invisible to the naked eye, are an adequate meal. Not the spores but the fungal mycelia are the favourite menu for storage mites [45].

Damage due to domestic mites is of a clinical order only and may result in allergic diseases.

4

Allergic disease

Allergic diseases occur after sensitization to allergens, usually followed by a hyperreactivity to irritants. This only happens if a genetic predisposition exists and exposure to allergens takes place. Persons with such a genetic heritage are called atopic. 20 to 40% Of the Dutch population is atopic [12]. Sensitization towards allergens is assessed by means of an intracutaneous skin test or by measurement of blood serum immunoglobulins of class E (lgE} concentrations against a specific allergen.

Allergens are predominantly protein-polysaccharides that elicit an immune response of lgE-producing cells [5]. Domestic allergens are produced by rodents, pets, moulds, mites and other arthropods such as cockroaches. In this thesis the focus will be placed on domestic mites and air-borne moulds.

The severity of the allergic disease can be judged by the level of total blood serum lgE concentration and by the level of blood eosinophils. Allergic diseases are expressed as respiratory symptoms or eczema accompanied by severe pruritus. The diseases are known as asthma, rhinitis and atopic dermatitis. In the case of atopic dermatitis, symptom scores may be used to assess the severity of the disease. In the case of asthma, lung function measurements are performed to estimate severity.

In infancy (less than 1 year old) atopic dermatitis may be the first sign of allergic disease. It is frequently due to exposure to food allergens. Later on (from the age of one year onward) sensitization to indoor allergens becomes a major cause of allergic inflictions [16]. If a child spends more time outdoors, outdoor allergens, such as pollen, can also influence the development of the allergic disease. Typically, allergic disease develops from atopic dermatitis in infancy to asthma or rhinitis later in life. A combination of symptoms also occur. After some period of allergen exposure, the respiratory systems becomes hyperreactive and start to react to all sorts of irritants (such as cigarette smoke) in concentrations not irritating to non-atopies. Atopic dermatitis usually dimin­ishes at higher ages, whereas symptoms due to asthma, chronic bronchitis and lung emphysema (Chronic Obstructive Pulmonary Diseases or COPD) increase. The cost to society amounted to 1 billion guilders a year in 1985 for COPD and asthma patients [50].

Allergy due to mites is a world-wide problem. 5 to 30% Of the world population is allergic to mites [48]. Large numbers of house dust mites (Pyroglyphidae), the producers of house dust allergens, were discovered in the early sixties, independently, by a Dutch, a Japanese and a French scientist [4;43;59]. Mite allergy in houses is considered to have its main cause in expo­sure to house dust mites. Allergens produced by domestic mites are actually digestive enzymes of the mites and are for a great part excreted with their faeces. Fungal allergens are located in the spores and in the mycelium. In addition they are released in the air [25;29]. Several studies around the world have shown that exposure to house dust mites is related to asthma, rhinitis and atopic dermatitis.

Allergy due to storage mite exposure in houses was seen before World War II. After World War II storage mite allergy was occupationally related and seen in rural surroundings only. From the eighties onward an interest in storage mite allergy reappeared. Nowadays, storage mite allergy is not only related to occupation or seen in the rural population, but is also common in the urban population [3;21 ;32;42].

5

More than 40 % of the patients allergic to house dust mites also have an allergy to storage mites [20;33]. This conflicts with the fact that storage mites represent only a minor fraction of the total mite population in house dust [9;60]. No significant difference in allergenicity is reported among the species [60].

Allergen exposure

Exposure to irritants or inflammation of the skin and mucous membranes may exacerbate the disease, but exposure to domestic aero-allergens in houses is the main cause of allergic inflictions [24]. Therefore, prior to avoidance measures, the extent of the allergen exposure is determined. Exposure to domestic allergens is monitored thro1.1gh biological sampling. Samples are taken from the floor, furnishings or air. For moulds, the number of spores or colony forming units (CFU) are used as variables. To assess mite exposure, mite numbers, mite allergens or guanine, a nitrogen waste product of arachnids, are assessed.

Measurement of mite-exposure is primarily focused on the determination of house dust mites (pyroglyphids) exposure, because they are the dominant mite species in the house dust ecosystem. Before World War II, however, storage mites (Acaridae and Glycyphagidae) accompanied by fungi were the most common inhabitants of the dwellings. They developed in home-textiles and on wall surfaces [49]. After World War II, the dramatic changes in building design, use and nature of home-textiles and house-cleaning procedures resulted in a shift of exposure in dwellings from storage and other fungal eating mites to house dust mites [6]. The prevailing dust mites adapted to xerophilic conditions.

Individual house dust mite allergens were isolated and a distinction made between group I allergens (Der p I) and group II allergens (Der p II) [5]. Der p I concentrations in house dust correlate positively with the mite excretion­product concentration of guanine and with total mite numbers [11 ;37]. Guanine content in house dust is easily assessed semi-quantitatively by means of the Acarex® test (AIIergopharma Joachim Ganzer KG, Reinbek, Germany). In this way, mite-allergen exposure can be checked by inhabitants.

Dust mite exposure has been judged for an international threshold value. Values higher than 100 mites per gram mattress dust, or 10 mites per gram floor dust, or 2000 ng Der p I per gram dust or 0.6 mg guanine per gram dust are considered as a risk factor for sensitization [48]. For mould exposure, however, no such standard exists.

Moulds form a group of biological agents that have been subject of study for many centuries. Before Christ ( ± 1300 BC) the advice was given to remove plasterwork in a building ridden with moulds [38]. In the 1930s, the presence of moulds in dwellings was found to be related to building and health damage [35].

Dampness in dwellings may cause the occurrence of fungi and concurrently rheumatoid arthritis [55]. Several mould species belonging to the genera Aspergillus, Cladosporium and Penicillium elicit positive skin reactions in atopic persons [10;28]. 10 to 30% Of the atopic persons are allergic to moulds [10].

In the last 10 years, different surveys have again been completed among inhabitants living in humid buildings, to examine the relation of humidity with well-being and health problems [14; 15;53;58]. Respiratory symptoms were found to be significantly correlated to with dampness and mould spots in houses [ 14; 58]. This relationship was also demonstrated in the seventies [57].

6

Allergen avoidance

Allergen avoidance was recently defined as follows: a set of measures to reduce exposure to relevant allergens or irritants, while leading to a reduction of clinical symptoms [13).

Allergen avoidance used to be limited to removal of mite-infested objects from the bedroom and the increase of ventilation in the house [22;35]. This type of sanitation was satisfactory in the thirties, because there was a storage mite population directly dependent on mould growth and the use of natural furnishing materials [6). In the seventies, this method of 'conventional sanitation' was still applied to a dust mite allergy. By this time, however, another fauna had developped (mainly Pyroglyphids) that was less dependent on high humidity and able to inhabit a wide range of furnishing materials. The technically effective avoidance measures from the thirties were still prescribed without paying attention to actual mite allergen exposure.

The 'conventional sanitation' has become less adequate. Some allergic patients living in houses that are sanitized conventionally, still maintain high mite allergen exposure and allergic complaints. Only after a selective mite avoidance programme was executed, the symptoms of rhinitis patients dimin­ished [33). Selective mite avoidance encompasses detection and control of noxious levels of allergen producers and eradication of these hazards and their allergens in allergologically relevant allergen reservoirs.

Allergen avoidance measures nowadays comprise use of mattress encasings, acaricids, washing of textiles, and control of indoor humidity [24;33;52]. Relocation of patients to improved ventilated houses or to environ­ments hostile to mites, such as mountains and hospital, is also done [34;47;54]. Hospitalization, however, results in a temporary improvement of allergic symptoms, since back in the home allergen exposure reappears. The different avoidance measures are often applied singly [18]. In this way they do not always result in clinical benefit. From the eighties onward the allergologi­cal control of house dust revived, partly due to the purification of the major house dust mite allergens [171 and the use of guanine detection for mite infestation [1 '1]. Still in some mite avoidance studies the monitoring of mite exposure is neglected [ 181.

Research done by the Interuniversity Task Group "Home and Health" has shown that (a) management of dust allergens in home textiles is possible through control of house dust with the Acarex· test (guanine detection) and through the execution of a short term selective mite avoidance programme [33] and that(b) several measures are technically effective in the control of allergenic mites and fungi in house dust. This resulted in the devise of a modern concept of mite avoidance. This modern mite avoidance concept comprises both short-term mite avoidance measures and long-term mite prevention measures [52]. The clinical success of tt:lis modern mite avoidance concept has not yet been wholly evaluated. Beside this, reduction of mites in home-textiles was the focal point. Indoor walls and room partitions were not included in avoidance programmes until now.

7

Aim of the study

Aim of this study is to investigate the possible role of indoor walls and room partitions in allergen exposure leading to atopic symptoms of the inhabitants. Building as well as maintenance characteristics of the houses are taken into account. In order to design effective structured allergen avoidance programmes a multi-disciplinary approach will be tried. To understand the ecological rela­tionship on humid walls and room partitions biological sampling of these niches is foreseen. Through the management of causative moulds, mites and other arthropods, we expect to be able to design preventive measures.

Outline of the thesis

Ecological relationships of indoor walls and room partitions will be examined in the laboratory and in the home environment (Chapters 11.1, 11.2). laboratory studies (Chapter II. 1) will be performed under stationary conditions with domestic mould and mite species. Topics include:

Effect of organic soiling on mould growth on indoor surfaces (11.1.1 ); Allergen excretion, assessed by guanine concentration, of dust-eating (Pyroglyphidae) and mould-devouring mites (Acaridae and Glycyphagidae) (11.1 .2); Stability of the mite allergen Der p I under simulated domestic conditions (11.1.3).

Home studies (Chapter 11.2) will be carried out in houses of atopic persons. Topics include:

Relationship between moulds, mites and moisture on inner walls (a pilot study) (11.2.1 ); Interrelations of mites, dust lice and fungi on damp walls and room parti­tions (11.2.2); Allergenic mites on mineral walls and in home-textiles (11.2.3).

Economic damage, mainly health damage, will be evaluated from the view point of preventing relevant allergen exposure. The possibilities for an extension of home-sanitation programmes to walls and room partitions is explored (Chapters 111.1, 111.2, 111.3). Topics include:

History of storage mites research from an allergological point of view (111.1 ); A multi-disciplinary home-sanitation programme involving the cleaning of mineral surfaces and ventilation improvement (a case study) (111.2); Clinical and technical efficacy of mite avoidance measures (an open study) (111.3).

Finally, the results will be discussed (Chapter IV) in an integrated fashion, that should lead towards symptom reduction of the inhabitants of the house. Summaries are given in English and Dutch.

8

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fecundity of three species of grain store mites on fungal diets. Exp & Appl Acarol. ( 1991 ); 12: 297-302.

46. Pitt Jl, Christian JHB. Water relations of xerophilic fungi isolated from prunes. Appl Microbial. ( 1968); 16: 1853-1858.

47. Platts-Mills TAE, Mitchell EB, Nock P, Tovey ER, Moszoro H, Wilkins SR. Reduction of bronchial hyperreactivity during prolonged allergen avoidan­ce. Lancet. ( 1982); 25: 675-678.

48. Platts-Mills TAE, de Week AL Dust mite allergens and asthma- a worldwide problem. J Allergy Clin lmmunol. (1989); 83: 416-427.

49. Reh L. Ueber Wohnungsmilben. Zeitschrift fur Desinfektions- und Gesund­heitwesen. (1925); 17: 122-124.

50. Rutten-van Molken M, Doorslaer EKA van, Rutten FFH. CARA in cijfers: verslag van een pilot-study. Institute for Medical Technology Assess­ment, State University Limburg, Maastricht. (19891: 70 pp.

51. Sinha RN. Acarina community in the stored rapeseed ecosystem. In: Acarology VI. eds: Griffiths DA, Bowman CE. (1984); 2: 1017-1025. ·

52. Schober G. Control of allergenic mites and fungi in house dust. Ph.D. thesis, Utrecht, the Netherlands. (1991 ): 179 pp.

53. Tammes E, Borst de AR, Huitink BM. lnventarisatie vocht-en schimmelpro­blematiek in woningen. Bouwcentrum, Rotterdam, the Netherlands. ( 1982) report nr: 6362.

54. Spieksma FThM, Zuidema P, Leupen MJ. High altitude and house dust mites. Br Med J. (1971 ); 1: 82-84.

55. Varekamp H. De betekenis van behuizing en houtrot voor het ontstaan van reumatoi'de arthritis. Ned Tijdschr Geneeskd. (1960); 104: 862-868.

56. Varekamp H, Spieksma FThM, Leupen MJ, Lyklema AW. House-dust mites in their relation to dampness of houses and their allergen content of house dust. Proc. Vth lnterasma Congress. (1966): 256-268.

57. Varekamp H, Leupen MJ. Vochtige woningen en astma: Onderzoek naar het verband tussen vochtigheid en klachtenpresentatie, uitgevoerd in 580 woningen te Leiden. IG-TNO. Werkrapport D 35. (1973): 79 pp.

58. Verhoeff AP. Home dampness, fungi and house dust mites, and respirato­ry symptoms in children. Ph.D. thesis, Rotterdam, the Netherlands (1994): 191 pp.

59. Voorhorst R, Spieksma-Boezeman MIA, Spieksma FThM. Is a mite {Dermatophagoides sp.) the producer of the house-dust allergen? Allergie und Asthma. (1964); 10: 329-334.

60. Voorhorst R, Spieksma FThM, Varekamp H. House-dust atopy and the house-dust mite Dermatophagoides pteronyssinus {Trouessart 1897). Stafleu, Leiden. {19691: 159 pp.

11

12

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.1 LABORATORY STUDIES

I I .1.1 ORGANIC SOiliNG AND MOULD GROWTH ON INDOOR SURFACES (published in the Proceedings of the international CIB W67 Symposium on Energy, Moisture and Climate in Buildings. CIB Publication 121 19901

13

14

ORGANIC SOILING AND MOUlD GROWTH ON INDOOR SURFACES

Helianthe S.M. Kart\ L.G.H. Koren\ G. Schober1 and CHR. Korf2

1) Interuniversity Task Group "Home and Health", Utrecht State University and Eindhoven University of Technology, the Netherlands.

2) Stichting Centrum voor Oppervlaktetechnologie (COT) Haarlem, the Netherlands.

ABSTRACT

Extensive mould growth occurs in about 20% of Dutch houses. Visible mould growth on indoor surfaces is considered unsightly or may cause allergic inflict­ions such as asthma, bronchitis, rhinitis and conjunctivitis. In in-vitro experi­ments, fungal development was compared on the following clean and soiled building and furnishing materials: concrete, brick, lime-sandstone, two types of plaster, spruce wood, mattress and carpet. The substrates were kept in a high humidity environment at room temperature for 35 to 105 days. In the case of clean surfaces placed on agar plates visible mould growth occurred on neutral and slightly acidic substrates only. Clean carpet and mattresses not placed on agar, although having a neutral pH, remained free from visible fungal growth for more than 7 months. All soiled surfaces were fungal to the same extent within 7 weeks. In houses the influence of surface pH on mould growth is eliminated by deposition of dust and other organic substances even in quantities invisible to the naked eye. To prevent fungal damage, floors, walls and ceilings should be smoothed and be easy to clean.

INTRODUCTION

Visible mould growth in houses presents health risks. In atopic persons sensiti­zation or development of allergic symptoms may occur [1]. The musty smell is discomforting and discolouration of building material surfaces by moulds is considered unsightly [2]. Furthermore, mould growth may lead to deterioration of building materials. An excess amount of moisture, often caused by decreased ventilation for energy-saving purposes, is usually the prime cause of mould development. In about 20% of the Dutch dwellings visible mould growth occurs [3]. Fungal growth in house-dust, stored food and on walls occurs in combination with mites and dust lice [4;5]. Each species has its own specific minimal, optimum and maximal value for a number of parameters. Important parameters for mould growth include temperature, light, pH of the substrate, air velocity, availibility of nutrients and water molecules [5].

In this study a comparison is made of fungal development in relation to water activity (Awl and surface pH on both clean and soiled surfaces of building and furnishing materials: brick, lime-sandstone, concrete, sprayed-on plaster, gypsum plaster, spruce wood, mattress, carpet. Aw is defined here as the ratio between water-vapour pressure present in the air over the surface and the saturated vapour pressure in air at the same temperature. It is related to relative humidity as: Aw e. R.H.(%)/100.

15

MATERIALS & I')IIETHODS

Substrates tested

The following building and furnishing materials were tested: a} brick, bl lime­sandstone, c) concrete, d) sprayed-on plaster, e) gypsum plaster board, f) spruce, g) mattress, h) carpet. Mattresses were assembled from two layers 4 mm polyether and mattress tick, stitched together in usual patterns. Except for mattress and carpet, the substrates are rather hygroscopic. An indicative measurement of the pH-values of the building materials was performed, by comparing the colour of drops of pH-indicator fluid (Merck for the first six substrates and Hellige for the other two) on the materials to reference colours (Table 1 ).

Three experiments were performed: The first one with clean surfaces (5x5 em) placed on agar plates [alto f)], the second one with clean surfaces (10x10 em) not placed on agar plates [e) to h)], the third experiment with artificially soiled surfaces (10x10 em) not placed on agar plates [also e) to h)]. The dust used was an analogon of the artificial dust used in cleaning industries, modified to be comparable to natural house dust [6].

Fungi

Clean surfaces placed on agar were inoculated with three different fungal combinations. 11 Alternaria species, Aspergillus niger van Tieghem, Cladosporium species, Coniophora puteana (Schum. ex Fr.) Karst, Penicillium brevicompactum series. Scopulariopsis brevicaulis (Saccardo) Bainier, Serpula lacrimans (Wulf.) Bond (representing the fungal flora of cellar and crawl space) [7]; 21 A. glaucus group, A. versicolor group, A. niger van Tieghem, P. brevicompa­ctum series, S. brevicaulis (Saccardo) Bainier, S. lacrimans (Wulf.) Bond. (representing the fungal flora of bathroom and kitchen) [71; 3) A. glaucus group, A. restrictus group, A. versicolor group, P. brevicompa­ctum series, S. brevicaulis (Saccardo) Bainier, Wallemia sebi (Freseniusl von Arx (representing the fungal flora of carpet and upholstered furniture) [7]. Fungi were grown on malt agar (combination 1 and 2) or malt-sucrose agar (combination 3) in petri-dishes (diameter 10 em).

Experiments on clean and soiled surfaces not placed on agar plates, were all performed with A. repens (Corda) Sacc.

Experimental set-up (figure 1)

Clean surfaces placed on agar plates. Malt agar (Oxoid; Aw = 0.99) and malt-sucrose agar (Oxoid; Aw = 0.95) dishes (diameter 10 em) were used. Inoculation with the 6 or 7 different species took place at 0.5 em distance from the edge at equally divided positions on an imaginary circle of 28 em in circumference. One thallus per species was cul­tured. After detection of growth of all inoculated species, experimental sub­strates were placed in the centre of the inoculation circle, and culturing was continued for 6 weeks. Each week mould growth was assessed visually and results after 40 weeks were noted.

In the fifth week, relative air humidity above the agar plates was deter­mined with a hygroscope (Rotronic AG, Zurich, Switzerland). Relative humidity ranged from 95.3% to 97.8% after malt agar incubation, and from 93.8% to

16

94.4% after malt-sucrose agar incubation. The temperature of the environment was quite constant, mean value being 17.1 ± 0.3 degrees centigrade.

Clean surfaces not placed on agar plates. A. repens (Corda) Sacc. was grown on malt agar slants in glass tubes. A spore suspension of A. repens (3.5 million spores/miL for convenience called fungal combination 4, was prepared by washing malt agar slants with distilled water containing 0.02 % Tween-80. A blood cell counting chamber (Burker-Turk, Hofheim, Germany) was used to assist adjustment of spore concentration. Prior to inoculation of this xerophilic species, substrates were acclimated at 75.0% ( ± 1.3%, hygroscope measurements) relative humidity and 22-24 degrees centigrade (in air-tight polythene bags containing glass beakers with saturated ammonium sulphate) in a cupboard. Inoculation was performed by pipetting 0.1 ml of the spore suspension in three aliquots in a diagonal line onto the experi­mental substrates. The substrates were placed in 15 em diameter glass petri­dishes and covered with poplin. Mould growth was determined under a binocu­lar microscope (20x), at first every week, and later on every 4 weeks.

FIGURE 1. Mould growth after 15 weeks 01;1 gypsum plaster board on agar inoculated with a fungal combination (left) and on gyPJum plaster not placed on agar after 40 weeks (right) at 75 % relative humidity and 22 - 24 C

17

Soiled surfaces not placed on agar plates. Soiling was performed with 0.5 g (spruce wood, plaster) or 1 g (mattress, carpet) artificial dust [6] by rubbing it on or into the material. The set-up for soiled surfaces was identical to the set-up for clean surfaces not placed on agar. After 15 weeks, a 1x1 em matrix was placed above the test surfaces and the number of squares with and without fungal growth was determined. Results were expressed as the number of positive squares, ranging from 0 to 100. Statistics were performed by use of the T-test based on range with a confi­dence level of 0.01 (8].

RESULTS

After 6 weeks incubation, 4 of the 6 building materials on agar plates showed visible mould growth. On the alkaline surfaces (concrete and lime-sandstone) no fungal growth was noted. On neutral materials (brick, plaster) and slightly acidic ones (spruce wood) mould growth was considerable at water activities of 0.94 and above. Alkaline sprayed-on plaster also had a remarkable fungal growth. Clean building materials showed little fungal growth at a water activity of 0. 75 after 40 weeks incubation. On mattress and carpet at the same water activity no fungal growth was observed (Table 1 ).

After 7 weeks all soiled surfaces were covered with moulds. In some cases a slight contamination with other species was noted; the contaminating fungi belonged to the genera Aspergillus, Penicillium and Scopulariopsis. However, the inoculated fungus A. repens remained the prevailing fungus on the experimental surfaces. No difference in fungal development was observed on materials with 0.5 g or 1.0 g artificial dust (Table 2).

TABLE 1. Mould growth on clean materials after 4() weeks incubation and ~er 6 weeks incubation in malt ~ar or malt-sucrose arr. f-1 = no fun,al growth, [ + 1 = little ngal growth, [ + + 1 = definite

ngal growth, [ + + + = strong funga growth

Surface material pH Fungal combination Aw Agar yes/no Fungal growth

concrete 10-12 0.97 yes

lime-sandstone 10-12 0.97 yes

sprayed-on plaster 10-12 2 0.97 yes ++ 3 0.94 yes ++

brick 6-7 0.97 yes ++

gypsum board 6 2 0.97 yes ++ 3 0.94 yes ++ 4 0.75 no +

mattress 5-6 4 0.75 no

carpet 5-6 4 0.75 no

spruce wood 5 1 0.97 yes +++ 4 0.75 no +

18

TABLE 2. Fungal development on soiled materials aJ 75 % relative humidity and 22- u· C qfter 15 weeks ina{b_ation, expressed as arithmic mean (X), standard deviation (s) and range of numbers of pos1t1ve squares

Surface material Dust applied in g Fungal development

X s range

gypsum board 0.5 93 ±9 75-100

spruce wood 0.5 94 ±lO 72-100

carpet 1.0 93 ±7 SHOO

mattress 1.0 96 ±9 75-100

DISCUSSION

Clean alkaline materials placed on agar do not promote fungal growth, not even at high relative air humidity. Sprayed-on plaster is exceptional, probably because old plaster is less alkaline than fresh plaster. On soiled materials moulds grow to a more or less equal extent, indifferent of the surface pH of the underlaying material (Tables 1 & 2).

From these and other studies [9; 1 OJ the importance of local water activity for mould growth becomes evident. The Aw of clean materials depends on the nature and structure of the material, on relative air humidity and on tempera­ture. On spruce wood and gypsum plaster board more fungal growth occurs at higher water activity. After 40 weeks incubation clean carpet and mattress showed no fungal growth at all; the nature of these materials does not promote mould growth (Table 1 ). On soiled materials fungal growth is excessive even at low relative air humidity (Table 2). After soiling, the extent of fungal growth is equal on all 4 indoor surfaces. In the case of soiling the water activity of the surface depends on the nature of the dust and not on the nature of the underlaying material; the high Aw of dust stimulates fungal growth and increases the mould development rate.

CONCLUSIONS

The pH of the surface of building and furnishing materials is probably not important for the development of moulds under home conditions.

Naturally soiled surfaces are ust.~ally more susceptible to fungal growth than clean surfaces, even at low relative air humidities. Dust stimulates mould development.

Since indoor surfaces in dwellings inevitably become soiled, mould growth can not be prevented by using mould resistant materials. Therefore building and furnishing materials in dwellings should be smoothed and be easy to clean. Smooth materials are less susceptible to dust adherence. Frequent cleaning prevents mould growth by reducing dirt, thereby retarding mould development.

19

ACKNOWLEDGEMENT

We are grateful to mr. J. Scharringa and mr. H. Vos for aiding in sampling and analysis. We also want to thank the Stichting voor Minibiologisch Onderzoek (SMO) and the Gesellschaft fur hausbiologische Forschung mbH for financial support.

REFERENCES

1. Mallea, M., Charpin, J. Moissisures. Allergologie, 2nd edition, ed. Charpin, J., Flammarion Medecine-Sciences, Chevilly-Larue, France, pp. 242-259 (1986).

2. Kart, H.S.M, Bronswijk, J.E.M.H. van, Schober, G. Moulds, mites and moisture. A preliminary report on six cases of fungal damage in dwell­ings, in Present and future of indoor air quality, eds. C.J. Bieva, Y. Courtois, M. Govaerts. Elsevier Science Publ., pp. 389-393 (1989).

3. Adan, O.C.G. Zin en onzin over vocht in gebouwen, Vakblad voor biologen 67, 15, pp. 290-294 (1987).

4. Kart, H.S.M. Mites, dust lice, fungi and their interrelations on damp walls and room partitions. Proc. Netherlands Entomological Soc., vol.1, Amsterdam, eds. M.J. Sommeijer, J.v.d.Biom, pp. 63-68 (1989).

5. Bronswijk, J.E.M.H. van. House Dust Biology for allergists, acarologists and mycologists, NIB publishers, Zeist (Netherlands), pp. 151-165 (1981).

6. Schober, G. Synthetischer Hausstaub als Substrat fOr allergenerzeugende Hausstaubmilben (Dermathophagoides farinae, D. pteronyssinus, Acari: Pyroglyphidae). Allergologie; 14: 140-143 (1991).

7. Bronswijk, J.E.M.H. van. House Dust Biology tor allergists, acarologists and mycologists, NIB publishers, Zeist (Netherlands), pp. 166-167 (1981).

8. Snedecor, G.W., Cochran W.G. Statistical methods. 6th edition, Iowa State University Press. Ames. 593 pp (1967).

9. Morgenstern, J. Einfluss von Polyvinylacetat-Zuslltzen in Putz-mortel auf die Schimmelbildung. Material und Organismen; 17: 241-251 (1982).

10. Grant, C., Hunter, C.A., Flannigan, B., Bravery, A.F. The moisture require­ments of moulds isolated from domestic dwellings. Int. Biodeter; 25: 259-284 ( 1989).

20

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.1 LABORATORY STUDIES

11.1.2 MOULD-DEVOURING MITES DIFFER IN GUANINE EXCRETION FROM DUST-EATING ACARI, A POSSIBLE ERROR SOURCE IN MITE AlLERGEN EXPOSURE STUDIES!to be published in an international biomedical journal)

21

22

MOULD-DEVOURING MITES DIFFER IN GUANINE EXCRETION FROM DUST-EATING ACARI, A POSSIBLE ERROR SOURCE IN MITE ALLERGEN EXPOSURE STUDIES

Helianthe S.M. Kort, G. Schober, L.G.H. Koren, J. Scharringa Interuniversity Task Group "Home and Health", Utrecht State University and Eindhoven University of Technology, the Netherlands.

ABSTRACT

Measurement of guanine in dust proved a good assessment of mite allergen exposure. Exposure to mite allergens may lead to atopic inflictions. In a semi­natural test system the development of Dermatophagoides pteronyssinus (Trouessart) and Glycyphagus domesticus (De Geer), and the presence of their guanine excretion, was examined in a dust-soiled and mouldy environment. Mites were counted after heat-escape, and guanine was detected by means of capillary zone electrophoresis. For each species, 50 mites randomly taken, were inoculated on soiled test­surfaces of 10 x 10 em. Rough wooden board, gypsum board, tufted carpet, and self-made mattress representing wall surfaces and home-textiles respective­ly were used. Eight weeks after inoculation with mite only, the surfaces were all mould ridden, and mite and guanine measurements were taken. The Spearman rank correlation test and the Mann-Whitney U-test were used in statistical analysis. The confidence limit was set at 1%. Among the various test-surfaces, no differences were found regarding total mite numbers and amount of guanine present (p > 0.01 ). For the dust-eating mite D. pteronyssinus, total mite numbers correlated with the amount of guanine present (p = 0.002) on all inoculated surfaces, indicat­ing feeding on the protein-rich dust. For the mould devouring mite G. domes­ficus, however, no such correlation was found (p = 0. 72). Apparently, they mainly consumed fungal carbohydrates during this experiment. The allergological relevance of storage mites has been under discussion for the last 25 years. In humid homes, these mites will feed almost exclusively on fungi and may produce allergenic or irritating substances different from those arising on protein-rich laboratory media used in allergen extract production or present in carpets, bedding and furniture.

INTRODUCTION

Domestic mites, especially house dust mites (Pyroglyphidael, are common inhabitants of houses. Exposure to mite allergens may lead to atopic inflictions such as rhinitis, asthma and atopic dermatitis [11. The significance of exposure to house dust mite (HOM) allergens in these disorders has been well docu­mented [2]. In the eighties, the significance of exposure to storage mites (SM) in allergic diseases, however, was established in rural communities only, and was related to damp environments and agricultural occupations [3;4;5]. At present, several studies reporting SM allergy in combination with HOM allergy not only in rural areas, but also in urban and sub-urban surroundings [6;7].

Home textiles as well as wall surfaces may be inhabited by both types of mites [8;9]. Mite excretion products, guanine and allergens, are measured in the

23

dust to deduce mite exposure, before an individual avoidance plan is made up [10]. In addition, the efficacy of mite avoidance measures can be easily assessed by the measurement of guanine [1;11].

In houses, HOM and SM share the same niches, although their feeding differs [12]. However, when storage mites (Acaridae and Glycyphagidae} occur, their growth coincides with fungal growth [9;13].

Mite development and fungal growth depends on the availability of water, and to a lesser extent to the presence of nutrients or predators in the niche. Under suitable conditions, mites and moulds prosper, and produce allergens in clinically relevant amounts [8;14].

Some studies report about cross-allergenicity between HOM and SM allergens. Other studies revealed distinct HOM and SM allergens [reviewed in 15].

Guanine measurement is an important tool in the evaluation of avoidance studies with all species of mites. Therefore, we examined the correlation between HOM and SM and their guanine excretion in a soiled and mould-riaden environment.

MATERIAL AND METHODS

The domestic mites, Dermatophagoides pteronyssinus (Trouessart) and G/ycyp­hagus domesticus (De GeerL were reared at room temperature and 55%, 75%, 85%, 88% or 90% relative humidity, under stationary conditions. Mite allergens were assessed by guanine determination. Simulated dwelling conditions were created as described for a semi-natural test system [1 0; 16].

Organisms used were derived from our own laboratory cultures. For each species, 50 mites randomly taken were put on each test-surface. Test-surfaces used were pieces of 10 x 10 em of rough wooden board, gypsum board, tufted carpet and self-made mattress, representing wall surfaces and home-textiles.

Different relative humidities (RH) were achieved by the following satu­rated salt-solutions: calcium nitrate (55% RH), ammonium sulphate (75% RH), potassium chloride (85% RH}, sodium bicarbonate (88% RH). Beside these salt­solutions we also used water to achieve a RH of ;;;::: 90%. Equilibrium situation were assessed with a moisture meter (Rotronic AG, Zurich, Switzerland).

Experimental set-up All surfaces were soiled prior to acclimatization. Textile surfaces were soiled with 1.0 g of artificial dust and smooth surfaces with 0.5 g [ 171.

After soiling, the surfaces were put in a microwave at 450- 550 Watts for one minute. These microwaved and soiled surfaces were acclimatized in polyethylene bags (ARE, Polypax b.v., Barneveld, the Netherlands) for 2 weeks. These bags were placed in a cupboard in a stationary environment of T = 20 °C, and RH = 55% (mean values).

In each bag 8 surfaces were enclosed: two of each surface type. Surfaces were placed in petri-dishes, and their rims were covered with tangle trap (The Tanglefoot Company., Grand Rapids, Michigan, USA). The dishes were covered with a poplin cloth, and tied with an elastic band by hand.

After two weeks, the surfaces were inoculated with 50 mites each. Two blanks were used; both microwaved but with no organisms added.

Every two weeks, the surfaces were aerated for 10 seconds by gently waving of the hands above the surface. The whole experiment was repeated after one week.

24

Analysis Eight weeks after inoculation, analysis was performed. Contaminating fungi were scored by means of a grid with a 1 x 1 em matrix, as large as the test­surface. Fungal scores ranged from 0 to 100.

A tape-imprint was also taken of each surface in order to identify the contaminating fungi. These tapes were inoculated for 3 weeks on Oxoid-malt agar with water activities of 0.99 and 0.82 [9], after which mould colonies were identified.

Mite analysis was done by vacuuming each surface for 25 seconds. In the collected dust a rough estimation of the numbers of living mites was made. This was done by examining the dust for 1.5 minute under a dissecting micro­scope (10 x magnification) and counting the moving mites. Following, a more accurate estimation of the number of remaining living mites was made by use of the heat-escape method [18].

Guanine was quantitatively assessed in the collected dust by means of capillary zone electrophoresis (CZE) [19] (10 mM Tartaric acid, B-Aianine, pH 3; capillary of 50 em in length, internal diameter 50 p, 30 kV, detection at 254 nm). A Beckman p/ace system 2000 (Beckman Instruments, California, USA) was used. Results were expressed as guanine in pM per gram dust.

Statistical analysis The Spearman rank correlation test and the Mann-Whitney U test were employed. The confidence limit was set at 1%. Statistical analysis was per­formed by use of SPSS-pc version 4.0.1 [20].

RESULTS

At the end of the experiment, all surfaces were mould ridden. The contaminat­ing moulds belong predominantly to the species A. repens and P. chrysogenum. Other mould taxa found include Mucor racemosus, Paecilomvces variotii and Cladosporium.

D. pteronvssinus was present in a range of 0 - 1750 per dish (median = 18). The maximum number of D. pteronvssinus was found on spur wood at 75% RH. G. domesticus mites were present in a range of 0- 1098 per dish (median = 27). The maximum number of G. domesticus was also present on spur wood at 75% RH.

The blanks stayed free of mites but they were covered with moulds to the same extent as the surfaces inoculated with mites. Indicating that the moulds originated from the dirt used for soiling. Between blanks and surfaces inhabited by D. pteronvssinus the amount of guanine differed significantly (p = 0.0002). However, no significant difference was found in guanine content between blanks and surfaces populated with G. domesticus (p = 0.02).

Among the various test-surfaces, no differences were found regarding total mite numbers and guanine (p > 0.01 }. Consequently, all results were grouped by relative humidity only. The soiling of the surfaces with moulds was equal for all types of surface, except for spur wood and gypsum board inocu­lated with G. domesticus. Gypsum board surfaces inoculated with G. domesti­cus were more covered with moulds, as compared to spur wood populated by G. domesticus (p = 0.008).

25

Table 1: Spearman rank correlation (rs) matrix of the variables guanine content, total mites, guanine I mite, and relative humidity (RH) for D. pteroayssinus and G. domesticus. In each cell N = 96. Significant correlations are in oo"ld type

Guanine content

Total mites

Guanine I mite

Humidity (RH)

G. domesticus

Guanine content

ts - 0.18 p O.o7

rs 0.26 p 0.01

Total mites

rs = 0.32 p = 0.002

rs = 0.68 p < 0.000001

Guanine I mite

ts -0.08 p 0.44

rs -0.96 p < 0.000001

D. pteronyssinus

Humidity (RH)

ts 0.10 p 0.32

rs = 0.37 p = 0.0002

rs = -0.38 p = 0.0001

As was found previously [8;21 ;22], total mite numbers of both species correlated with the relative humidity. However, the amount of guanine excreted by D. pteronyssinus in the dust did not correlate with the relative humidity. On surfaces populated by G. domesticus, the amount of excreted guanine did correlate significantly with the relative humidity (rs = 0.26, N = 96, p = 0.01) (Table 1 ).

For the dust-eating mite D. pteronyssinus total mite numbers correlated significantly with the amount of guanine present (rs = 0.32, N = 96 p = 0.002). For the mould devouring mite G. domesticus, however, no such correla­tion was found. For both mite species total mite numbers were negatively corre­lated with the amount of guanine per mite (Table 1 ).

DISCUSSION

Measurement of guanine has shown to be a good assessment of mite allergen exposure. Previous studies did show a correlation between guanine and mite group I allergens and between guanine and mite numbers [23;24]. The correla­tion between guanine in mattress dust and mite numbers did however disappear when mattresses were previously vacuumed [24]. In this study guanine was correlated with total mite numbers in the case of the dust-eating mite D. pteronyssinus. In the case of colonization by the mould-devouring species, G. domesticus, no such relation was found. This indicates that in mite avoidance studies, assessment of guanine in mouldy environments underestimates the exposure to storage mites. Mite allergens being digestive enzymes, feeding differences may result in differences in faecal pellet composition. A shift from nitrogenous (guanine) to more carbohydrate-rich may be expected, due to the fungal diet of storage mites. This could be an explanation for the variability found in cross-allergenicity studies of storage mites and house dust mites [reviewed in 15].

In mite avoidance studies, humidity mal'lagement has proven to be successful in reducing mite numbers. For rapid results a combination with short­term procedures, such as acaricidal cleaning, is advised [10;25]. In this study the ambient relative humidity influenced the number of mites. Guanine excretion

26

on surfaces inhabited by D. pteronyssinus is not related to ambient humidity, indicating no increase of protein digestion by humidity in the range of 50 - 90% relative humidity. On surfaces colonized by fungi-eating G. domesticus, humid­ity did increase the guanine amount in the dust, probably by the association of humidity with mould growth.

The relevance of storage mites in allergic disorders has been under dis­cussion for the last 25 years [26]. In humid homes, these mites will feed almost exclusively on fungi and may produce allergenic or irritating substances dif­ferent from those arising on protein-rich laboratory media as used in allergen extract production. We conclude that the different feeding habits of Dermatophagoides and Glycyphagus may explain some error on exposure assessment by guanine determination.

ACKNOWlEDGMENTS

We are grateful to drs. P.H. Aelmans, drs. M.J.LM. Bancsi, mrs. W.W.C. van der Horst-Cator, mr. H. Vos and drs. L.H.M. Walters for aiding in mite and fungal analysis and ir. M.J. van der Schans for explaining guanine analysis with capillary zone electrophoresis. We thank Stichting Minibiologisch Onderzoek (SMO), the Netherlands for, financial support.

REFERENCES

1 . Dust mite allergens and asthma: Report of a second international workshop. J Allergy Clin lmmunol. 1992; 89: 1046-1060.

2. Colloff MJ, Ayres J, Carswell F, Howarth PH, Merrett TG, Mitchell EB, Walshaw MJ, Warner JO, Warner JA, Woodcock AA. The control of allergens of dust mites and domestic pets: a position paper. Clin Exp Allergy. 1992; 22 (suppl 2): 1-28.

3. Cuthbert OD, Brostoff J, Wraith DG, Brighton WD. 'Barn allergy': asthma and rhinitis due to storage mites. Clin Allergy 1979; 9: 229-236.

4. Hage-Hamsten M van, Johansson SGO, Hoglund S, TOll P, Wiren A, Zetterstrom 0. Storage mite allergy is common in a farming population. Clin Allergy 1985; 15: 555-564.

5. Wraith DG, Cunnington AM, Seymour WM. The role and allergenic importance of storage mites in house dust and other environments. Clin Allergy 1979; 9: 545-561.

6. Dal Monte A, Tomasini C, Calipa V, Pederzoli P. The role of the sensitization to storage mites in the diagnosis of allergic respiratory diseases. Aerobio­logia. 1992; 8: 419-422.

7. De belie M, Lanner A. H~ufigkeit von spezifischen lgE-Antikorpern gegen Hausstaub- und Vorratsmilben bei jungen Atopikern. Allergologie. 1993; 8: 323-328.

8. Bronswijk JEMH van. House dust biology for allergists, acarologists and mycologists. NIB publishers Zeist, the Netherlands, 1981: 316 pp.

9. Kort HSM. Mites, dust lice, fungi and their interrelations on damp walls and room partitions. Proc. Exper. & Appl. Entomol., N.E.V. 1990; 1: 63-68.

10. Schober G. Control of allergenic mites and fungi in house dust. Ph.D. thesis, Utrecht, the Netherlands 1991 : 179 pp.

27

11. Chapman MD. Guanine- an adequate index of mite exposure? Allergy 1993; 48: 301-302.

12. Rodriguez JG, Rodriguez LD. Nutrional ecology of stored-product and house dust mites. In: Nutrional ecology of insects, mites, spiders, and related invertebrates. eds: Slansky F, Rodriguez JG. New York, John Wiley, 1986: 345-368.

13. Sinha RN. Acarina community in the stored rapeseed ecosystem. In: Acarology VI. eds: Griffiths DA, Bowman CE. Ellis Horwood limited, Chichester, 1984; 2: 1017-1025.

14. Bronswijk JEMH van, Rijckaert G, Lustgraaf B van de. Indoor fungi, distribution and allergenicity. Acta Bot. Neerl. 1986; 35(3): 329-345.

15. Hage-Hamsten van M. Allergens of storage mites. Clin Exp Allergy 1992; 22: 429-431.

16. Koren LGH. Simulating dwelling conditions for mite-population studies, a laboratory model. Proc Exper Appl Entomol, N.E.V. 1993; 4: 151-156.

17. Schober G. Synthetischer Hausstaub als Substrat fUr allergenerzeugende Hausstaubmilben (Dermatophagoides farinae, D. pteronyssinus, Acari:Pyroglyphidae). Atlergologie 1991; 14: 140-143.

18. Bischoff E, Fischer A, Wetter G. Untersuchungen zur Okologie der Hausstaumilben. Allergologie 1986; 9: 45-54.

19. Verheggen ThPEM, Everaerts FM. Equipment for multifunctional use in high­performance capillary electrophoresis. J. Chromatogr 1993; 638: 147-153.

20. Norusis M, SPSS/PC+ Statisticstm 4.0 for the IBM pc XT/AT and PS/2. 1990, SPSS inc, Chicago JL (USA).

21 . Edney EB. Water balance in land arthropods, (Zoophysiology & Ecology vol 9). Springer, Berlijn, 1977: 282 pp

22. Hughes AM. The mites of stored food and houses. Ministry of Agriculture, Fisheries and Food. Technical Bulletin no. 9, 1976, London, 400 pp.

23. Le Mao J, Pauli G, Tekaia F, Hoyet C, Bischoff E, David B. Guanine content and Dermatophagoides pteronyssinus allergens in house dust samples. J Allergy Clin lmmunol 1989; 83: 926-933.

24. Bronswijk JEMH van. Guanine as a hygienic index for allergologically relevant mite infestations in mattress dust. Exper Appl Acarol. 1986; 2: 231-238.

25. Kort HSM, Koers WJ, van Nes AMT, Young E, Vorenkamp J, Wolfs BG, Bronswijk van JEMH. Clinical improvement after unusual avoidance measures in the home of an atopic dermatitis patient. Allergy 1993; 48: 468-471.

26. Spieksma FThM. Domestic mites: their role in respiratory allergy. Clin Exp Allergy 1991; 21: 655-660.

28

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.1 LABORATORY STUDIES

11.1.3 FOUR-YEAR STABILITY OF DfR pI IN HOUSE DUST UNDER SIMULATED DOMESTIC CONDITIONS (published in Allergy 1994; 49: 131-1331

29

30

Alley}• 1994c 49: 131-133 Printed in Belgium - all rights rest!rt'f!d

Short Communication

Cop1·ri~:ht <D .\lunksgoard 1994

ALLERGY ISSN 0105·4538

Four-year stability of Der p I in house dust under simulated domestic conditions in vitro

Kort HSM, Kniest FM. Four-year stability of Der p l in house dust under simulated domestic conditions in vitro.

H, S.M. Kort 1, F. M. Kniest2

1 1nteruniversjty Task Group "Home and Health", Eindhoven University of Technology, Eindhoven. The Netherlands, and

Allergy 1994: 49: 131-133. © Munksgaard 1994.

' Allergopherma Joachim Ganzer KG, Research~Prevention {F·Praevl Division, Hambu'lJ. Germany

For almost 4 years, the stability of Der p I was assessed by RAST inhibition in bouse-dust samples incubated under simulated domestic conditions {5 or 25, C and 75% relative humidity). Der p I concentrations were determined before heating dust samples at 60¢C to kill the mites, and at 0, 6, 14, 2 L and 4 7 months after heating. Heating at 60' C for 24 h caused no significant change in Der p I concentration. After a 4 7 -month incubation under simulated domestic conditions, reduction of Der p I was still not obvious. It is concluded that even after extermination of mites, home textiles remain allergen reservoirs for an extended period of time.

Key words: avoidance programs; Der p l; house dust; house-dust mites.

A voidance schemes should take this into account.

The stability of mite allergens in vi I'D is important for avoidance procedures. Various avoidance schemes have been developed to reduce mite allergen expo­sure (2). Most avoidance measures are based on the extermination of mites and removal of their allergens by use of chemicals, or by dehydration of their niche by humidity management.

The success of the measures is assessed in air dust samples or in house-dust samples, vacuumed from the top of the dust reservoir. It was shown, however, that mites are present not only in the top layer of mattresses, but also in older dust deeper in the mat­tress (3).

The concentration of Der p I, a house-dust mite allergen, is one of the variables, in addition to mite counts and guanine content, used to measure the allergenicity of house dust in order to control mite allergens in homes of mite-allergic patients. This study was undertaken to assess the stability of Der p I in house dust, which remains behind in the mite niche after mite extermination measures have been taken.

Material and methods

Three dust samples were taken from two Dutch homes: I) sample A from a carpet in the living room

Accepted lor publication 11 May 1993

(Utrecht), 2) sample B from a carpet in a bedroom, and 3) sample C from a mattress (last two in Valk­enswaard). Dust was collected with a Hoover S 2222 vacuum cleaner (550 W, Hayesgate, UK), by vacu­uming with an intensity of 1 min/m2

• The dust was analyzed for mites by a flotation method according to van Bronswijk {II). Subsequently, two aliquots of 5 g were weighed from each sample.

Mite extermination was done by dry-heating the 5-g subsamples at 60°C for 24 h in an open tube. After this treatment, the subsamples were incubated at 75~-;, relative humidity (RH) and 5°C to simulate floor conditions, or at 75~.-;, RH and 25"C to simu­late furniture and mattress conditions. Samples were stored in glass tubes of 2.5 x 5.5 em, closed with a screw cap.

Der p I concentrations were determined in IOO..mg aliquots taken 6 months before heating and after at 0, 6, 14, 21, and 47 months of incubation. The RAST inhibition test was used in duplicate (12) (Centraal Laboratorium voor de .Sloedtransfusiedienst (CLB), Amsterdam, the Netherlands). Statistical analysis was performed with the arithmetic mean values. The Mann-Whitney U-test (10) was used, and the con­fidence limit was set at 5%.

Most avoidance procedures exterminate mites but leave most fungi viable (9). In this study, domestic

31

Kort and Kniest

Table 1. Anhropods present in hoose·dust samples before heating, and givon in num­bers per gram dust

Samples

A

Mites Dermatophagoides larinae a D. pteronyssinus 25 621 446 Storage mites 5 Gamasina 10 12.5 Cheieytidae 2.5 2.5 Other mites• 38 8.5

Total mn.s 40 682 457 Dust lice 5 10

• In sample 8: Tarsonemini and Oribatei; in sample C: Tawnemini, Oribatei, and Chor­toglyphus arcuatus.

conditions during an avoidance situation are simu­lated. Heating to 60°C of house dust results in the extermination of mites (4), while still leaving some fungal activity (8) that may decompose proteins in the dust (11).

Results D. pteronyssinus was present in all dust samples. D.farinae was present only in bedroom floor dust

(sample B). In addition to house-dust mites (90%), non-Pyroglyphid mites and dust lice were identified (Table !).

The concentration of Der p I was not changed by heating at 60°C for 24 h. The increase of 33-43% of the Der p I concentration over preheating mea­surements was not statistically significant (P < 0. 3 5). For over I year, Der p I remained constant; after 14 months, an increase was seen, except for sample A, which had a relatively low starting concentration. Again, changes were not statistically significant.

In dust samples incubated at 5°C for almost 4 years, 50% to 90~~ of the Der p I concentration found immediately after heating could be detected. In dust samples incubated at 25°C, 29~~ to 50% of the starting Der p I concentration after heating was found (Fig. l). However, dust samples incubated at 5 or 25 o C did not differ statistically in Der p I con­centration. In fact, none of the changes in time were statistically significant.

Discussion All changes found in Der p I concentrations can be explained by the natural heterogeneity of the domes­tic dust (11 ). Therefore, neither heating to 60" C nor storage for 4 years influenced the Der p I concen-

100000 100000 s ·c 25 ·c

Sample

~ 10000 ~

10000 ~A " -o -o

i ~ IB .s lc 0. 0.

" " 0 Cl

1000 1000

100

-8 6 21 -8 8 21

t t MOntns

Fig. 1. MeanDer p I concentrations (RAST inhibition results) before heating (arrow) and over period of almost 4 years after heating of house-dust samples, incubated at 5'C and 75~~ RH to simulate floor conditions (left) or at 25'C and 75~~ RH to simulate furni­ture and mattress conditions (right). Der p l concentrations are expressed in ngjg dust and plotted on logarithmic scale. Sample A =carpet. home near Utrecht (Netherlands). Sample B =carpet, home in Valkenswaard (Netherlands). Sample C =mattress, home in Valkens­waard (Netherlands).

32

tration. In whole mite extracts, incubated at 23 oc for l and 3 months, 75% of the starting Der p I content could still be detected (I).

It has been shown before that Der p I, in aqueous extract of D. pteronyssinus, may remain intact after heating at 56 o C for 24 h, but after a 1-h heating, a five- to 10-fold reduction in IgE antibodies binding was seen, whereas heating for 1 hat 75oC reduced the binding 100-fold (6). In our study, heating of house dust at 60oC for 24 h did not denature Der p I either. Apparently, Der p I is more stable in native house dust than in solution.

At the start of this study, both bedroom dust samples (mattress and floor) had Der pI concentra­tions above the suggested allergologic risk level of 2000 ng of Der p I per gram dust (7). After almost 4 years' incubation, Der p I values were still higher than this risk level. This indicates that even after extermination of mites, home textiles remain allergen reservoirs for extended periods of time. Therefore, in mite allergen avoidance programs it is desirable to combine mite extermination with allergen removaL

In the near future, we will examine the stability of Der p I under better simulated home conditions such as those devised by Schober et al. (9) and extended by Koren (5).

Acknowledgments We thank Dr G. Schober and Mr H. Vos for aiding in sampling and analysis and also the Gesellschaft fUr hausbiologische For­schung, Germany. and Stichting Minibiologisch Onderzoek. the Netherlands. for financial support.

4-Year stability of Der p I in house dust

References I. ACKLAND J, STEWART GA. Quantitation and thennal sta·

bility of the mite allergen DPT 12 in whole mite extracts. J Allergy Clin lmmunol 1984: 74: 848-54.

2. COLLOFF MJ, AYERs J. CARSWELL F, et al. The control of allergens of dust mites and domestic pets: a position paper. Clin Exp Allergy 1992: 12 {Suppl. 2): 1-28.

3. DE BOER R, VAN DEl< GEEST LPS. House-dust mite (Py­roglyphidae) populations in mattresses, and their control by electric blankets. Exp Appl Acarol 1990: 9: 113-22.

4. KINNAIRD CH. Thermal death point of Dermawphagoides pteronyssinus (Trouessart, 1897) (Astigmata, Pyroglyphidae), the house dust mite. Acarologia 1974: 16: 340-2.

5. KoREN LGH. Simulating dwelling conditions for mite­population studies. a laboratory model. Proc Ex per Appl En­tomoll993: 4: 151-6.

6. LOMBARDE!<O M. HEYMAN PW, PLATTS-MILLS TAE, Fox JW, CHAPMAN MD. Conformational stability of B cell epitopes on group l and group II Dermatophagordes spp. al­lergens. Effect of thermal and chemical denaturation on the binding of murine lgG and human lgE antibodies. J lmmunol !990: 144: 1353-60.

7. PLA TIS-MILLS T AE. DE WEeK AL. Dust mite allergens and asthma- a worldwide problem. J Allergy Clin Immunol 1989: 83: 416-27.

8. SCHMIDT-LORENZ W. Hitze.Jnaktivierung von Schim· melpilzen und Hefen in Lebensmitteln. In: -Schweizerische Gesellschaft fllr Lebensmiuelhygiene ( SG LH ). Schimmelpilze und Hefen in Lehensmiueln: Vortrage. gehalten am ETH­Fortbildungskurs "Nachweis und Dilferenzierungvon Schim· melpilzen und Hefen in Lebensmitteln". Dielsdorf: Chemische Rundschau, 1977: 28-35.

9. SCHOBEl< G. KNlESTFM. KORTHSM. DE SAINT GEORGES GRIDELET DMOG. VAN BRONSWIJK JEMH. Comparative efficacy of house dust mite extermination products. Clin Exp Allergv 1992: 22:618-26.

10. SIEGiL S. Nonparametric statistics for the behavioral sci­ences. New York: McGraw-Hill. !956: J 16-27.

1!. vAN BRONSWIJK JE:V!H. House dust biology. Zeist: NIB­publisher, 1981: 33--17. 1-16-50, 258.

12. WIDE L UPPSALA MD. BE:-<NICH H. JOHANSSON SGO. Diagnosis of allergy by an in ritro test for allergen antibodies. Lancet l%7: 1105-7.

33

34

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.2 HOME STUDIES

11.2.1 MOUlDS, MITES AND MOISTURE, A PRELIMINARY REPORT ON SIX CASES OF FUNGAL DAMAGE IN DWELLINGS (published in the proceedings 'Present and future of indoor air quality. eds: C.J. Bieva, Y. Courtois, M. Govaerts. Excerpta Medica, Amsterdam. ISBN 0-444-81134-6. 1989: 389-393)

35

36

MOULDS, MITES AND MOISTURE, A PRELIMINARY REPORT ON SIX CASES OF FUNGAl DAMAGE IN DWElliNGS

Helianthe S.M. Kort, Johanna E.M.H. Van Bronswijk, Gerd Schober Interuniversity Task Group "Home and Health", Utrecht State University and Eindhoven University of Technology, the Netherlands.

INTRODUCTION

Visible mould development in houses occurs on hygroscopic materials, such as partitions, ceilings, and furnishings. The inconvenience to the inhabitants consists of an unsightly view and development of air-borne allergens. Approxi­mately 20% of the 5.1 million Dutch homes appears to be affected [1]. The allergenicity of indoor growing fungal species of the genera Aspergillus, Cladosporium and Penicillium, has been firmly established [2,3].

In other fungal niches, such as stored products or house dust, the moulds are present in ecosystems consisting of insects and/or mites in addition to fungi [4,5]. The mites may also cause health damage by allergen contamination of indoor air. Fungal mites of the superfamily Tarsonemoidea, as well as the storage mites Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae are considered relevant in house dust allergy, next to house dust mites (Pyroglyphidae) only [6, 7].

In general, water availability is the most active limiting factor for the develop­ment of moulds as well as mites under indoor conditions [5,8]. Therefore, in this study, we report on relationships between occurrence and abundance of fungi and their required moisture level, as well as on sampling of arthropods sharing a niche with fungi on damaged mineral material in houses.

MATERIAl AND METHODS

In 6 cases of mould damage, careful inspections were made of all partitions and ceilings. Damaged sites were described (Table 1 ). Sampling included a 4-fold application of adhesive tape (23 mm wide Scotch Magic Tape). The tape was wrapped around two fingers and pressed 4 times at the same spot, after which it was applied to a microscopic glass slide for transportation. From each of the 19 different tape samples taken, about 7 cm2 was used for direct light micro­scopic analysis for fungi and arthropods. Four other tape squares were employed to inoculate agar plates (Oxoid-Malt with 0.82 water activity, Oxoid-Malt with 0.95 water activity, normal Oxoid-Malt and Czapek [5]). Sam­ples were taken from 6 damaged sites, by scraping a surface of 4 cm2

• In the laboratory the dust was suspended in 10 ml 50%-saccharose solution. Aliquots of 0. 1 ml were used for the inoculation of Malt agar plates with a water-activity of 0.82 and 0.95. No attempt was made to extract arthropods from the scrapings. Homes 1 & 2 were considered dry by the inhabitants; in the other houses the indoor climate was described as more or less damp.

37

TABLE 1. Discoloured sites in six houses, sample-coding used, type of sampling, and assessment of dampness of indoor climate by the inhabitants

home room site site description sam~lin1 discolouration number code(*) number me od **)

Bd 1 ceiling, W s green-brqwn Li 2 facade, N, left T+S green Stf!peS Li 3 facade, N, right T+S green stnpes

2 Ba 1 ceiling, W, above shower s yellow~ink Ba 2 ceiling, W 1 m from shower s yellowjgink Li 3 facade, NE comer, 0.2 m heig!lt T yellow green Li 4 facade, NE comer, 1. 8 m height T yellow/ green Li 5 facade, NE comer, 2.0 m height T yellow Li 6 facade, N, behind picture frame T yellow-brown Li 7 facade, N, behind picture T yellow-brown

3 Ce 1 exterior wall! ceilinf, T no discoloration Ha 2 hall-wall/at comer o toilet T flufJi: Li 3 exterior wall/facade, 0.2 m height T no 1scoloration Li 4 interrior wall 0.2 m height T no discoloration Li 5 back-side cupbOard/intenor wall T yellow/green

4 Ba 1 above shower, S T black dots Ba 2 about 1 m from shower, S T black stripes Ki 3 facade, N, 0.2 m height T green Li 4 facade, N, 0.2 m height T grey-brown Li 5 facade, N, 1.0 m height T grey-brown

5 Li 1 facade, SW T black Li 2 side-front, NW T+S green-yellow

6 Bd behind mirror T black dots

<i>a =bathroom ~**)

= scrape method Bd =bedroom T = tape method Ce = cellar Ha =hall Ki =kitchen Li = living-room

RESULTS

Viable moulds were isolated from 17 of 19 tape samples and all scrape samples (Tables 1 & 2). The commonly identified fungal species belonged to the genera: Aspergillus (Eurotium), Cladosporium, Mucor, Penicillium, Phoma, and Wallemia (Table 2). In addition, the following taxa were isolated once in one or more samples: Acremonium strictum, Alternaria alternata, Aspergillus fumigatus, Cladosporium matrosporum, C. sphaerospermum, Doratomyces, Penicillium citrinum, P. digitatum, P. expansum, P. verruculosum, and yeasts.

Xerophilic species, pioneers able to develop below a water activity of 0.80, were pronounced in dwellings 1 and 2. These species are common in house dust, even under -technically speaking- dry conditions (indoor climate class II) [8]. Since the inhabitants also assessed the indoor climate as dry, it might well be that -just as in the case of house dust organisms- the water currently available to the micro-organisms originates from the indoor air, not from excessive moisture in the mineral substrate. In the past, some technical incident may have caused surface condensation or another mechanism for a temporary increase in substrate moisture, enabling the fungi to germinate.

The bathroom of dwelling 2 forms a special case (sites 2 Ba 1, 2 Ba 2) with Phoma as the only coloniser, causing the white surface to turn beautifully

38

yellow and pink. The species identified are known as plant pathogens and soil inhabitants [13]. Their yeast-like appearance might be an explanation for their absence, until now, from lists of dwelling damaging fungi.

At the other end of the moisture spectrum we see dwelling 3, with species of Mucor thriving, organisms that require a more or less longstanding high humid­ity. Here, we might hypothetize that not only substrate moisture, but also water vapour from the indoor air is available. Apparently the moisture level has been high for some time, giving Mucor the opportunity to outcompete most xerophilic species.

Although only small surface areas were studied for arthropods, these organ­isms were found to be present in 4 out of 6 houses studied, always on walls, never on ceilings. On 2 occasions (1 Li 2 and 6 Bd 1) the numbers were high, up to 50 I 7 cm2! Mites collected, belonged to the orders Astigmata, mainly storage mites (24 of 32: genus Tyrophagus), Cryptostigmata, Prostigmata (34 of 40: family Tarsonemidae, Fungal mites), and Mesostigmata. All insects belonged to the Psocoptera (Dust or Book lice). Storage and Fungal mites were commonly seen in connection with conidial heads and conidia of Aspergillus. As was mentioned before, both Tyrophagus and Tarsonemid mites are sources of potent allergens.

Under the 'dry' conditions of dwelling 1 (site 1 Li 2) the Tarsonemid mites shared their niche with A. penicilloides and Wallemia sebi. Nutritional relation­ships between certain Tarsonemid species and mould taxa are well known [141. Unfortunately, the tape preparations were not suited for specific identification.

Behind a mirror in a bedroom of house 6 (6 Bd 1) not only the fungal flora indicated more or less longstanding water activities of 0. 78 (A. versicolor) to 0.82 (P. brevicompactum), but the mite fauna gave a hint too. The most common member of the mite genus Tyrophagus, T. putrescentiae, requires a relative humidity of 84% or more to thrive! Fungi form a complete food for this mite that has a special liking for A. versicolor [5].

The other 2 arthropod infested sites (4 li 5} and (5 li 1} only showed small numbers, so no definite ecological conclusions could be drawn. But even from our restricted material of 4 houses, it appears that in future studies of fungal damage, more work should be devoted to arthropods, with larger surfaces sampled and more taxonomical work done. This way it might be possible to find that 'damp' partitions containing a complete ecosystem, comparable to that of house dust.

CONCLUSIONS

1 . The occurrence of storage and fungal mites and insects, in addition to moulds, on 'damp' parts of mineral partitions and ceilings, presents a new concept in house ecology, and indoor allergy.

2. Certain species of organisms isolated, appear useful as biological sensors for physical factors, such as moisture. Availability of moisture may be deducted from the presence of such indicators. Future studies should include micro-measurements of humidity next to mite and fungal niches.

3. To make specific identification of mites and insects possible -a prerequi­site for an understanding of the 'damp wall ecosystem', as well as for the discovery of a greater number of biological sensors- the arthropods should be collected with a vacuum-cleaner, in addition to adhesive tape.

39

TABLE 2. Common moulds isolated, and number of arthropods I 7 cm2 directly identified from discoloured sites (for coding see table 1). The critical(= mmimal water-activity requirements (Aw min) of funga1 species ts indicated {5;9;10;11;12]

Fungi(*): 2 3 4 5 6 7 8 9 10 l1 12 13 14 Arthropods(*):

0.70 0.80 0.85- 0.93 15 16 17 18 19

site code

1 Bd 1

Li 2

u 3

2 Ba 1

Ba 2

Li3

Li 4

X

X

X

X

X

X X

X

X X X

X

X

X

X

Li 5 ------------------- no viable fungi ---------------------------------------

Li 6 X X

Li 7 X X X

3 Ce 1

Ha2

Li 3

Li 4

------------------ no viable fungi -------------------------------------------

u 5

4 Ba I

Ba2

Ki 3

u 4

Li 5

5 Li I

Li2

6Bdl

(*)

40

X

X

X

X

X

X

X

X

X

X X

X X

X

X X

X

X X

X X

X

X

X

Church

& Hochapfel

--- not sampled ---

4 16 2

-- not sampled ---

-- not sampled ---

2 5

6

26 19 2 3

ACKNOWLEDGEMENT

Financial support came from the Foundation SMO (Utrecht, the Netherlands). lng. A.J. Buis (Fiexchemie BV, Ridderkerk), ing. A. van der Aa and ir. P.C.H. van der Laan (Cauberg-Huygen BV, Rotterdam), ir. O.C.G. Adan and C.J.J. Castenmiller (IBBC-TNO, Rijswijk), mw. ir. A.M.S. Weersink assisted in sampling and damage inventarisation. Without their help this study would not have been possible. Prof.ir. J. Vorenkamp critically reviewed the manuscript.

REFERENCES

1. Adan OCG, Schober G, Kniest FM, Vorenkamp J (1988) Modification des conditions d'humidite a l'interieur de l'habitat: une methode d'assainissement de l'environnement allergenique. Rev Franc Allergol 28: 147-151.

2. Bronswijk JEMH van, Rijckaert G, Lustgraaf B van de (1986) Indoor fungi distribution and allergenicity. Acta Bot Neerl 35: 329-345.

3. Gravesen S (1979) Fungi as a cause of allergic disease. Allergy 34: 135-154.

4. Hurlock ET, Armitage DM, Uewellini BE (1980) Seasonal changes in mite (Acari) and fungal populations in aerated and unaerated wheat stored for three years. Bull Ent Res 70: 537-548.

5. Bronswijk JEMH van (1981) House dust biology for allergists, acarologists and mycologists. NIB, Zeist, the Netherlands.

6. Korsgaard J, Hallas TE (1979) Tarsonemid mites in Danish house-dust. Allergy 34: 225-232.

7. Lauter H ( 1988) Zur klinischen Bedeutung der Mil ben Glycyphagus destructor, Tyrophagus putrescentiae and Acarus siro im Vergleich zu Dermatophagoides pteronyssinus und Dermatophagoides farinae bei Hausstauballergien. Allergologie 11: 433-436.

8. Schober G (1989) Absolute indoor humidity and the abundance of allergen producing house-dust mite and fungi in the Netherlands. In: Present and future of indoor air quality. eds: Bieva, C.J., Courtois, M., Govaerts, M. Elsevier, Amsterdam, the Netherlands. 395-399.

9. Panasenko VT (1967) Ecology of microfungi. Bot Rev 33: 189-215. 10. Christensen CM, Kaufmann HH (1965) Deterioration of stored grains by

fungi. Ann Rev Phytopathol 3: 69-84. 11. Samson RA, Reenen-Hoekstra ES (1988) Introduction to food-borne Fungi.

Centraal Bureau Schimmelcultures, Baarn, the Netherlands. 12. Samson RA ( 1989) Centra a I Bureau Schimmelcultures, personal communi­

cation. 13. Doren bosch MMJ ( 1970) Key to nine ubiquitous soil-borne phoma-like

fungi. Persoonia 6: 1-14. 14. Krantz GW ( 1978) A manual of Acarology. Oregon State University,

Corvallis.

41

42

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.2 HOME STUDIES

1!.2.2 MITES, DUST LICE, FUNGI AND THEIR INTERRELATIONS ON DAMP WALLS AND ROIJI'I PARTITIONS (published in the proceedings of the Netherlands Entomological Society, N. E. V., Amsterdam. Experimental and Applied Entomology. eds: M.J. Sommeijer & J. van der Blom. N.E.V., Amsterdam. ISBN 9D-71912-05-1. 1990: 63-68)

43

44

MITES, DUST LICE, FUNGI AND THEIR INTERRElATIONS ON DAMP WAllS AND ROOM PARTITIONS

Helianthe S.M. Kort Interuniversity Task Group "Home and Health", Utrecht State University and Eindhoven University of Technology, the Netherlands.

ABSTRACT

Biotic relationships were studied within the biocoenosis of 74 humid indoor walls in 26 Dutch houses. Vacuum cleaning (59 walls) as well as taping (47 walls) were used to study mites, dust lice and fungi. The majority of walls and room partitions were inhabited by mites; while dust lice were present in about a third of cases. Most common arthropoda! taxa include the house dust mite Dermatophagoides pteronyssinus and predatory mites of the family Cheyletidae. Visible mould growth was discovered on 27 walls (37%). Arthropods were present in 16 out of 27 (59%) mould-ridden sites, as well as on 34 out of 47 walls (72%) without mould damage. Average mite numbers amounted to 1240 I g dust on walls with visible fungal growth, as compared to 556 I g dust on walls without. Although Tarsonemid mites did not favour mould sites, they appeared in greater numbers in the presence of xerophilic and meso-hygrophilic fungi, especially Aspergillus penicilloides, A. versicolor and Penicillium brevicompactum. Oribatids and Dermatophagoides farinae avoid excessive fungal growth. A typical wall biocoenosis consists of Pyroglyphidae, Glycyphagidae, Tarsonemoidea, Cheyletidae, Psocoptera and xerophilic as well as meso-hygrophilic moulds. Future biologic studies should aim at spatial relationships, succession and micro-effects of temperature and moisture availability.

INTRODUCTION

Mites, dust lice and fungi are common inhabitants of houses, that may cause damage to health as well as to building materials and furnishing (Kort et al. 1989; Bronswijk 1981). Three different indoor niches are inhabited by these organisms: house dust, stored food and feed, and damp or humid walls and room partitions. This last niche was recognized recently (Kort et al. 1989). This study concerns relationships within the new biocoenosis on walls with and without visible fungal growth.

MATERIAlS AND METHODS

74 Walls and room partitions were studied in 26 Dutch houses with health or building damage attributed to humid conditions. A vacuum cleaner (Hoover S 2907 A) was used to sample 1-8 walls I dwelling from top to bottom up to the skirting board, at an intensity of 1 min I m2 (20 homes, 59 walls in total). Dust was collected in a woven fabric (poplin, 65% polyester, 35% cotton, batiste) of about 80 cm2 placed in between nozzle and duct. On 47 walls and room partitions in 26 houses a tape method (Kort et al. 1989) was employed. Sites with (26 houses) and without (21 houses) possibly visible mould growth were

45

selected. Sites with visible growth are defined as discoloured fluffy areas, in which taping shows fungal hyphae on microscopic inspection. 32 Walls were vacuumed as well as taped.

Dust samples were weighed. Aliquots of 0.20 g or less (in the case of smaller samples) were analyzed with a flotation method for arthropods (Bronswijk, 1981). Squares of tape samples of about 2 cm2 were used for direct light microscopic analysis of fungi, mites and dust lice. Tape material from 15 walls (6 houses} was further cultured on agar plates: Oxoid-Malt with water activities of 0.99, 0.95 and 0.82, and Czapek (Kort et al. 1989).

Mounted arthropods and cultured fungi were identified with Brohmer (1964), Hughes (1976}, Krantz (1978), Onions (1981), Raper (1977) and Samson (1988).

Chi square tests at a 5% confidence level (Clarke, 1982) were used to compare abundance of arthropods on different sites.

TABLE 1. Arthropods isolated from 74 walls on sites with and without possible fungal growth, given in frequency, (F = numbers of walls infested) and in abundance (A = average on infested walls, expressliil as number I gram vacuumed dust or number I cm2 tape)

TAXON FUNGAL WALL NON-FUNGAL WALL

vacuumed taped total vacuumed taped total

n = 13 n = 26 n = 27 n 46 n = 21 n = 47

F A F A F F A F A F

no Arthropods 1I 11 12 20 13

Psoooptera 7 66 2 9 14 46 0 0 14

Acari (total)" 12 1240 7 15 16 34 556 2 3 34

Pyroglyphidae (total) 8 227 21 152

Dermatophagoides farina~!!' 2 5 3 144

D. pteronyssinus 8 85 16 65

Euroglyphus maynei 5 223 13 133

Acaridae 0 0 7 26

Glycyphagidae 8 122 11 182

Oribatida' 5 28 11 185

Mesostigmata 6 82 9 141

Tarsonemoideae• 4 981 6 32

Cbeyletidae 7 34 16 29

Tydeidae 0 0 67

Other Trombidiformes 5 1332 6 1582

Other Acari 0 0 2 6

• = significant difference (p < 0.05) in abundance between fungal and non-fungal walls.

46

RESUlTS

The dust yield per m2 wall varied from 0.3 to 2750 mg (median 10 mg). No difference was found between substrates: brick, plaster of Paris, wall-paper, wooden or jute wall-coverings. Arthropods were present on 78% of the vacuumed walls, mites on 75%, and dust lice on 36%. Corresponding figures for taped walls are: 21% with arthropods, 19% with mites and 4% with dust lice. Taxa present on 40% of the walls or more included the house dust mite Dermatophagoides pteronyssinus and the Cheyletidae, a predatory mite family (Table 1 ).

Frequency and abundance of arthropoda! taxa on walls with and without visible fungal growth differed (Table 1 ). When mites or dust lice occur on mould ridden walls, numbers are generally higher than on walls not damaged by fungal growth. This is especially true for the superfamily Tarsonemoidea. Other taxa, such as beetle mites (Oribatida) or the house dust mite D. farinae are more scarce on fungal hot spots.

Although arthropods were isolated from tapes as well as vacuumed dust, the two methods differ in their efficiency. Taping -when positive- shows higher numbers per surface area (up to 7 per cm2 = 70.000 I m2 , as compared to only 145 in the dust of 1 m2 wall.

In total 14 fungal species were reared from tapes of 15 walls. The majority of the 42 isolates belonged to meso-hygrophilic (55%) and xerophilic (29%) taxa (Kort et al. 1989). Pyroglyphid mites associate with xerophilic fungi; Glycyphagidae with meso-hygrophilic species, while Acaridae and Tarsone­moidea like both groups (Table 2).

TABLE 2. Combination frequencies qf fungi and acari on 11 tapes from visible mould sites

Fungi

Xerophilic

Aspergillus penicilloides

Wallemia sebi

Meso-hygrophilic

A. versicolor

Penicillium brevicompactum

DISCUSSION

Pyroglyphidae Acaridae Glycypbagidae

2

2

Tarsonemidae

2

Both vacuuming and taping were used in this study. Advantages of the former include a more extensive sampling area and species-identification of arthropods. The negative side of this sampling is disturbance of the spatial relations within the biocoenose. Fungi can not be identified qualitatively or quantitatively. Taping on the other hand supports a quantitative fungal analysis as well as insight in the structure of the biocoenose on site. It may be used as a quick screening method for fungi, but not for mites and other arthropods. In addition, species identification of arthropods is usually not possible.

47

The discrepancies in results between the two methods indicate that a mould saturated wall is in essence a hostile environment to the mites, that can only colonize through highly populated hot spots as is also known from stored grain (Sinha 1961 ). This is further supported by the fact that the average number of mites on colonized walls is highest in the presence of visible mould growth.

The dominant mite members of the house dust ecosystem, Pyroglyphidae and Cheyletidae (Bronswijk 1981) were also abundant on walls and room partitions, followed by the Glycyphagidae, a stored product family (Hughes 1976).

The combination of organisms on a certain site may be governed by the prevailing moisture conditions. The minimal water activities for development are known for most species found. Pyroglyphid mites (water activity for extensive growth 0. 70 - 0.80) in combination with xerophilic fungi (critical water activity 0.68- 0.80), but in the absence of stored product mites (water activity for fast development 0. 70 - 0.98) and meso-hygrophilic fungi (critical water activity 0.80 - 0.90) point at prevailing water activities of 0.80 and below (Bronswijk 1981 ). From the standpoint of the building engineer everything below water activity of 0.85 is considered dry (Pieysier 1986).

Apparently the wall biocoenose may be used as an indicator for micro­moisture conditions, an aspect warranting further study, as does succession, spatial relationships, and hygienic values for the exposure of the inhabitants to these potentially allergenic organisms.

CONCLUSIONS

1 . Visible fungal growth is a poor indication for mite infestation of indoor walls and room partitions.

2. A typical wall biocoenose consists of house dust mites (Pyroglyphidae), stored product mites (Giycyphagidae), fungal mites (Tarsonemoidea), predatory mites (Cheyletidae), dust lice (Psocoptera), and xerophilic and meso-hygrophilic moulds.

3. This biocoenose may be present on plaster of Paris, brickwork, wall­paper as well as on wooden and jute wall coverings.

ACKNOWLEDGEMENTS

The author is grateful to the inhabitants of the 26 houses for the opportunity to perform this study and for moral support. She also thanks drs. L.G.H. Koren, mr. J. Scharringa, drs. G. Schober and mr. H. Vos for aiding in sampling and analysis.

48

REFERENCES

Brohmer, P., 1964. Fauna von Deutschland. Quelle & Meyer, Heidelberg. Bronswijk J.E.M.H. van, 1981. House dust biology for allergists, acarologists

and mycologists. NIB Zeist. Clarke, G.M., 1982. Statistics and experimental design. Edward Arnold,

London. Hughes, A.M., 1976. The mites of stored food and houses, Ministry of

Agriculture, Fisheries and food, London. Kort, H.S.M. Bronswijk J.E.M.H. van, Schober G., 1981. Moulds mites and

moisture, a preliminary report on six cases of fungal damage in dwellings. - In: Present and future of indoor air quality, (C.J. Bieva, Y. Courtois, M. Govaeerts ed.): 389-393 Excerpta medica, Amsterdam.

Krantz, G.W., 1978. A manual of Acarology. Oregon State University, Corvalis. Onions, A.H.S., Allsopp, D. & Eggins, H.O.W., 1981. Smith's introduction to

industrial mycology. Edward Arnold, London. Pleysier, J.A., 1986. Schimmelgroei en bouwkundige eisen. - In: Bouwwereld

8: 49-53. Raper, K.B., Fennell, D.l., 1977. The genus Aspergillus. R.E. Krieger,

Huntington, New York. Samson, R.A., Reenen-Hoekstra E.S., 1988. Introduction to food-borne

fungi. Centraal Bureau voor de schimmelcultures, Baarn. Sinha, R.N., 1961. Insects and mites associated with hot spots in farm

stored grain. - In: Canadian Ent. 8: 609-621.

49

50

CHAPTER II ECOLOGICAL RELATIONSHIPS

11.2 HOME STUDIES

I I • 2. 3 AllERGENIC MITES ON MINERAl WAllS AND IN TEXTilES (published in the proceedings of the 1 st International Conference on Inset Pests in the Urban Environment. eds: K.B. Wildey & W.H. Robinson. BPPC Wheatons Ltd, Exeter. ISBN 0-9521824-0-8. 1993: 119-1221

51

52

ALLERGENIC MITES ON MINERAL WALLS AND IN TEXTILES

HELIANTHE S.M. KORT Center for Biomedical and Health-care Technology, Eindhoven University of Technology, PO Box 513, 5600MB

Eindhoven, The Netherlands

Abstract-In the home environment allergenic mites are well known inhabitants of textiles and food. In humid dwellings mites and moulds are found on walls.

In autumn (1990) textiles and wall surfaces were sampled in eight rooms of four dwellings. The same was done in winter (1990-1991), in seven rooms. Sampling was done with an intensity of I minutes vacuuming per square meter surface area.

In autumn as well as in winter the total number of mites from textiles and walls were statistically correlated. Spearman rank correlation coefficient being 0.731 (0.05<p<0.025) in autumn, and 0.667 (O.IO<p<0.05) in winter. In both periods a correlation between the number of house dust mites (HDM) from textiles and walls was also present (in autumn: p < 0.05, and in winter: p < 0.025). For both periods no association was found between the number of non-pyroglyphid mites from textiles and wall surfaces. The number of mites per square meter surface area was significantly lower on walls than in textiles.

The economical and health relevance of mites on walls is yet not clear. However, in the Netherlands about 20% of the housing stock has problems with dampness and moulds, which can lead to development of storage and fungal mites. Therefore, in humid dwellings control of allergenic domestic mites should include mites from walls.

INTRODUCTION

In the home-environment allergenic mites are well known inhabitants of home-textiles and food. In Europe the house dust mite, Dermatophagoides pteronyssinus, is the main allergen producer of allergens which may cause allergic inflictions, such as asthma (Piatts-Mills and de Week, 1989). Home-textiles, especially mattresses, show favourable conditions for mite development regarding humidity, temperature and food (van Bronswijk, 1981).

In the home-environment, damp walls are known as a susceptible substrate for mould growth (Grant, 1989), but are less known as a niche for mites. However, in 1934 it was already reported that the storage mite Glycyphagus domesticus occurred on mouldy wall paper (Hora, 1934). Recently, it has been found that in addition to storage mites, also house dust mites (Pyroglyphidae), fungal mites (tarsonemids) and predatory mites from the Cheyletidae family are present in wall dust (Kort, 1990). Other arthropods, like dust lice, were found next to a variety of mould species (Kort, 1989). All these organisms may also be present in house dust. They are known allergen producers, whose control may lead to a reduction in allergic symptoms (Colloff et al., 1992).

Therefore, we examined the interrelation between wall surfaces and home-textiles, in order to assess the importance of walls as a part of environmental control programmes.

MATERIAL AND METHODS

In autumn (1990), 17 home-textiles and 30 walls were sampled in eight spaces, of four different dwellings in the Netherlands. Sampling was done with an intensity of I minute vacuuming per square meter surface area with a Hoover S 2222 (550 Watts, Hayesgate, U.K.). In winter (199{}--1991), the same sampling procedures were repeated in seven spaces of four dwellings (24 home-textiles and 26 walls), of which three were also sampled in autumn. Another dwelling was chosen, because one of the dwellers moved and did not want to participate any more in the study.

After sampling took place dust samples were stored at room temperature prior to analysis. Analyses for arthropods were done with the flotation technique according to van Bronswijk, 1981. Mites found were arranged in the following categories: house dust mites (Pyroglyphidae), storage mites (Acaridae & Glycyphagidae), Tarsonemoidea,, Cheyletidae and other mites, which included oribatids, other Prostigmata and Mesostigmata. Arthropods found are expressed as arthropods per square meter. The maxima and medians are also given per 0.1 gram dust, because wall-dust samples were small ranging from 10 mg to 200 mg (median = 40 mg), and for comparison to other studies.

53

54

Guanine amount was estimated semi-quantitatively in the samples by use of Acarex"" (Werner & Mertz, Mainz, Germany).

Numbers of arthropods found on different walls in one single room were added to obtain the numbers of arthropods found on all walls in that particular room. The same was done with arthropods found in different home-textiles.

Statistical analysis was done by use of the Spearman rank correlation test for association of organisms in textile and on walls. The Mann Withney U-test was used to compute the difference between arthropods on walls and in textiles, and between arthropods found in autumn and in winter (Siegel, 1956). The confidence limit was set at 5%.

RESULTS

In autumn, the total number of mites/m2 ranged from 0-6, median = 2 for walls (maximum = 40 per 0.1 g, median = 5 per 0.1 g) to 0.1-311 for textiles, median = 38 (maximum = 183 per 0.1 g, median = 12 per 0.1 g) (Figure 1). In winter, total mite numbers/m2 from textiles ranged from 18 to 104, median= 39 (maximum= 50 per 0.1 g, median = 26 per 0.1 g). On walls however, 0-4 mite numbers/m2, median = 0.2 were found (maximum = 40 per 0.1 g, median = 5 per 0.1 g) (Figure 1). For both walls and textiles no significant difference is found between mites collected in autumn and in winter (p > 0.05), with the exception of the group of 'other mites' found on walls. Also no significant difference is found between mites collected in autumn and in winter, when only those spaces were compared, which were vacuumed both in autumn and winter. In winter significant less 'other mites' were found in wall dust. This was also the case for dust lice.

In autumn, in six of the eight spaces, textile-dust samples were above the proposed risk value of 0.6 mg guanine per gram (Acarex 1.20 for sensitization (Platts-Mills and de Week, 1989). In winter, in five of the seven vacuumed spaces, home-textile samples were above the risk value. In both seasons none of the wall dust samples were above the proposed risk value.

In autumn as well as in winter the total number of mites from textiles and walls, were statistically correlated. Spearman rank correlation coefficient being 0. 731 (0.05 < p < 0.025) in autumn, and 0.667 (0.10<p<0.05) in winter. However, the number of mites per square meter of surface area was sigl)ificantly lower on walls than in textiles (p<0.05) (Figure 1). In both periods a correlation l:)et\veen the number of house dust mites (HOM) from textiles and walls was also present (in autumn: p<0.05 and, in winter: p<0.025). In autumn, storage mites (SM) were found in textile as well as wall dust samples in two rooms only. During winter no SM could be collected from the wall dust. For both periods no association was found between the number of non-pyroglyphid mites from textiles and walls.

DISCUSSION

Within mite categpries, the number of mites on walls are not related to those in textiles, with the exception of pyroglyphid mites. However, total mite numbersjm2 are correlated for walls and textiles, this is probably contributable to the numbers in the category house dust mites only. The mite species found on walls are a reflection of those found in textiles.

In this study mite numbers found on walls are significantly lower than mites found in textiles as expressed in mite numbers/m2• This is as to be expected, since walls cannot be considered a mite allergen reservoir, as are home-textiles. Although, inner walls may be considered as a potential allergen accumulating surface, at sites with high infestation of mites and fungi. This is comparable to the hot spots known from stored grain (Sinha, 1961). It has been reported that the mite allergen Der f I has been detected in wall wipe samples at a concentration of 6.8 ng per filter (Wood, 1992).

Non-pyroglyphids from walls and textiles were not associated. The presence of non-pyroglyphids and fungi on walls may start as a local problem, when on the wall a moist spot turns into a favourable micro-habitat. Non-pyroglyphids such as storage and fungus eating mites, have been found in adhesive tape samples taken from walls, together with heads and conidia of Aspergillus (Kort, 1989). The relationship of pyroglyphid numbers in textiles and those found on walls, is probably due to aerogenic dust and mite transport, caused by domestic activities. It has been reported before, that house dust mites are the most abundant species on walls without visible mould

N E

N E

Textiles 350

300 A

250

200

150

100

50

0~~~~~~~~~ ZLA EL I CH I C83

ZLV Z81 U81 CK

200 Textiles

150 c

100

SQ

N E

Room Code

"' E

I

14

12

10

B

6

4

2

9

6

4

2

Walls

8

Walls

0

Arthropods

~ HOM

ISM !]r IIlii CH

!I OM

lOA

o o~~~~~~~~--~

Room Code P82

Fig. t. Mites and other arthropods isolated from textile- and wall dust samples taken in autumn 1990 (A & B) and in winter 1990-1991 (C & D).

growth, in contrast to fungal ridden wall surfaces, on which tarsonemids were the most abundant (Kort, 1990). It appears that on walls house dust mites are allochthonous organisms, whereas non-pyroglyphids are not.

The importance of mites in textile, in the sense of health care, has been acknowledged (Platts-Mills et al., 1992), though the economical and health relevance of mites on walls is yet not clear. However, in the Netherlands about 20% of the housing stock has problems with dampness and moulds (Tammes et al., 1985), and therefore, with storage and fungal mites. It is desirable to include walls in environmental control programs, not only because of the occurrence of moulds, but also because of the occurrence of allergenic domestic mites.

ACKNOWLEDGEMENT

I am grateful to the Stichting Minibiologisch Onder~oek (SMO), the Netherlands, who financially supported this study. I also want to thank mrs. W.W. van der Horst-Cator, drs. L.H.M. Walters and mr. J. Scharringa for their skilful technical assistance.

55

REFERENCES

1. Bronswijk van, J.E.M.H. (1981). House dust biology for a/Jergists, acarologists and mycologists. NIB publishers, Zeist (Netherlands). pp 105-127, pp 258.

2. CoUotr, M.J., Ayres, J., Carswell, F., Howarth, P.H., Merrett, T.G., MilcbeU, E.B., Walshaw, M.J., Wamer, J.O., Warner, J.A., Woodcock, A.A. (1992). The control of allergens of dust mites and domestic pets: a position paper. Clinical and Experimental Allergy. 22 suppl. 2: 1-28.

3. Grant, C., Hooter, C.A., Flannigan, B., Bravery, A.F. (1989). Tbe moisture requirements of moulds isolated from domestic dwellings. Int. Biodeterioration. 25: 259-84.

4. Hora, A.M. (1934). On tbe Biology of the mite Glycyphagus domeslicus de Geer. (fyroglyphidae, Acarina). The Annals of Appl Biology, 21:483-494.

5. Kort, HS.M., Bronswijk van, J.E.M.H., Schober, G. (1989). M011.lds mites and moisture. A preliminary report on six cases of fungal damage in dweltings. In presents and future of indoor air quality, eds. C.J. Bieva, Y. Courtois, M. Govaerts. Elsevier Science Pub!., pp 389-393.

6. Kort, H.S.M. (1990). Mites, dust lice, fungi and their interrelations on damp walls and room partitions. Proc. Netherlands Entomological Soc .. vol. I, Amsterdam, eds. M.J. Sommeijer, J.v.d. Blom, pp 63-68.

7. Platts-MiUs, T.A.E., de Wed, A.L. (1989). Dust mite allergens and astbma A world wide problem. J Allergy Clin lmmunol. 83: 416-427.

8. Platts-MiUs, T.A.E., Thomas, W.R., Aalberse, R.C., Vervloet, D., Chapman, M.D. (1992). Dust mite allergens and asthma: report of a second international workshop. J Allergy Clin Immwwl.. 89: 1046-60.

9. Siegel, S. (1956). Nonparametric statistics for the behavioral sciences. New York: McGraw-Hill. pp 116 ·127, pp 202-213. 10. Sinha, R.N. (1961). Insects and mites associated with hot spots in farm stored grain. The CanadiQJI Entomologist. 8:

609-621. 11. Tammes, E., Borst de, A.R., Huitink, B.M. (1985). lnventarisatie vocht- en schimrnelproblematiel:: in woningen.

56

Bouwcentrum, Rotterdam, The Netherlands. report nr: 6362. 12. Wood, R.A., Mudd, K.E., Eggleston, P.A. (1992). Tbe distribution of cat and dust mite allergens on wall surfaces. J

Allergy Clin lmmunol. 89: 126-130.

CHAPTER Ill HEALTH DAMAGE

I I I .1 VORRATSMilBENFORSCHUNG AUS AllERGOlOGISCHER SICHT lzu veroffentlichen in einer internationalen biomedizinischen Zeitschrift)

57

58

VORRATSMILBENFORSCHUNG AUS ALLERGOLOGISCHER SICHT

Helianthe S.M. Kort, Gerd Schober & Johanna E.M.H. van Bronswijk lnteruniversitare Arbeitsgruppe "Wohnung und Gesundheit", Universitat Utrecht und Technische Universitat Eindhoven, Niederlande

ZUSAMMENFASSUNG Vorratsmilbenforschung aus allergologischer Sicht

Milben der Fainilien Acaridae und Glycyphagidae, die gegenwartigen Vorratsmilben stehen bereits seit 100 Jahren im Interesse der allergologischen Milbenwissenschaft. Die Allergologen Prof. Dr. Karl Hansen, Prof. Dr. Georg Rost und Dr. med. Hermann Dekker veroffentlichten 1930 "Praktikum der allergischen Krankheiten". Die am meisten abundanten lnnenraumallergene jener Zeit waren Milben (Acaridae und Glycyphagidae) und Schimmelpilze. Hausstaubmilben (Pyroglyphidae) kamen Gberwiegend in getrockneten Tierhauten und in Vogelnestern vor. Nach dem zweiten Weltkrieg anderte sich die Art der Wohntextilien aus pflanzlichen Materialen und Fullungen zu synthetischen. Hausstaubmilben dominierten daraufhin in den Wohntextilien und das Interesse fUr Vorratsmilben lie~ im medizinischen Bereich nach. Acaridae und Glycyphagidae wurden zur Domane der Kammerjager. lnzwischen hat die Energiekrise von 1973 ihren Einflu~ ausgeubt und haben Energiespar­ma~nahmen zu Feuchteproblemen und zu Schimmelpilzwachstum auf Wanden und Zimmerdecken in Wohnungen gefuhrt. Kurzlich ist festgestellt worden, da~ Vorratsmilben auf diesen Pilzrasen in gro~en Mengen vorkommen. Die allergologische Bedeutung von Acaridae und Glycyphagidae hat in Stadtwohnungen in den letzten 1 0 Jahren wieder zugenommen.

Schlusselworter: Vorratsmilben - Hausstaubmilben Wohnungsmoblierung -Wende- Zimmerdecken- allergologische Bedeutung.

ABSTRACT Allergological aspects of storage mite research

For more than a hundred years, mites of the families Acaridae and Glycyphagidae, so called storage mites, have been of interest for allergological research. The allergologists prof.dr. Karl Hansen, prof.dr. Georg Rost and dr. Hermann Dekker, published "Praktikum der allergischen Krankheiten" in 1930. In this book domestic allergens are treated. The most abundant domestic allergens of that time were those of mites (Acaridae and Glycyphagidae) and moulds. House dust mites (Pyroglyphidae) only occurred on dry hides and in bird nests. After World War II, the type of home textiles changed from natural to synthetic materials and stuffings. House dust mites became the most abundant group in these textiles and the clinical significance of storage mites diminished. Acaridae and Glycyphagidae were only of interest to pest­controllers. Meanwhile, the energy crisis (1973) and the thermal insulation campaigns that followed, led to humidity problems in dwellings and to mould growth on walls and ceilings. Recently, it was found that storage mites occur on these mouldy spots. In the last 10 years, the allergological importance of Acaridae and Glycyphagidae in the domestic domain has again increased in urban areas.

59

Key words: storage mites - house dust mites - home textiles - walls allergological importance.

EINLEITUNG

Milben der Familien Acaridae und Glycyphagidae waren bereits dem Allergologen Professor Dr. Karl Hansen ( 1893-1962) bekannt. Bei der Medizinischen Abteilung des Montana Verlags in Horw-Luzern, Leipzig und Stuttgart erschien 1930 'Praktikum der allergischen Krankheiten'. Hansen schrieb das erste Kapitel Gber die Pollen-AIIergie, wah rend Professor Dr. Georg Alexander Rost ( 1877-19701 sich mit allergischen Hautkranken beschaftigte und Dr.med. Hermann Dekker das allergische Asthma beschrieb. Die drei Beitrage schlie!Sen gut aneinander an. Wir konnten vermuten, daB die Autoren ihre Beitrage untereinander gelesen und moglicherweise mit Kommentar versehen haben.

Rost und Dekker besprachen im 'Praktikum der allergischen Krankheiten' die Wohnungsallergene, wobei Dekker spezifisch auf Milben und Schimmelpilze hinwies. Dekker hat die Milben von Spezialisten, wie dem Deutschen Hermann Ludwig Wilhelm Graf Vitzthum von Echstaedt ( 1876-1942} und dem Niederlander Antonie Cornelis Oudemans ( 1858-1943), identifizieren lassen [12]. Die Milben gehorten den Familien Acaridae und Glycyphagidae an, das heiBt den gegenwartigen Vorratsmilben. DreiBig Jahre spater, in den sechziger Jahren, erregte die Familie der Pyroglyphidae allgemein groBe Beachtung und es lieB das Interesse fUr Vorratsmilben im medizinischen Bereich nach.

Heute sind die Vorratsmilben wieder ins medizinische Blickfeld zurGckgelangt. Haben wir also 30 Jahre lang die Daten als falsch angesehen?

Dieser Beitrag ist ein Versuch, einen groBeren Zeitraum des Wachstums und der Differenzierung der allergologischen Milbenwissenschaft transparenter zu gestalten. Ziel ist es, die zeitlichen okologischen Veranderungen der Allergenaussetzung in lnnenraumen zu beschreiben, und die historischen Entwicklungen in der Denkweise der allergologisch tatigen Mediziner zu verstehen.

HISTORISCHE RUCKBLICKE

Der allgegenwartige Hausstaub und seine Milben sind ein unerschopfliches Forschungsthema, obwohl in den letzten drei Jahrhunderten vie! Wissenswertes bekanntgeworden ist. Schon 1552 sanierte der italienische Arzt Gerolamo Carda no ( 1501-1576) das Bett des Erzbischofs von Edinburg, John Hamilton. Der Arzt verordnete das Wegwerfen der alten Federmatratze, eine neue Bettdecke aus ungesponnener Seide und ein neues Kopfkissen. Auch die Nahrung des Erzbischofs wurde eingeschrankt. Das Resultat war au!Sergewohnlich effektvoll und Cardano wurde gut bezahlt. Die asthmatischen Symptome des Erzbischofs verloren sich allmahlich [35].

Auch Antonia van Leeuwenhoek ( 1632-1723} konzentrierte sich auf das Studium von Hausstaub, mehr spezifisch auf die Milben, und zwar nicht aus allergologischer, sondern aus biologischer Sicht [27).

Allergologisch gesehen ist das Problem einfach zu beschreiben. Voorhorst und Spieksma auBern sich 1978 folgenderma!Sen: 'Hausstaub ist ( ... )letzten Endes die Gesamtheit aller Allergene aus der taglichen Umgebung des Allergikers'. Unseres Erachtens ist damit auch festgestellt worden, daB

60

Hausstaub und Hausstauballergene den zeitlichen okologischen Veranderungen in der taglichen Umgebung folgen. Nicht nur die hauslichen Kleinlebewesen, sondern auch das allergologische Denken der Wissenschaftler folgte den Zeichen der Zeit. Zwischen Empirie und Theorie blieb immer ein Spannungsfeld.

DIE GEBURT DES HAUSSTAUBALLERGENS

Wir schreiben 1921 beziehungsweise 1922, als Richard R. Kern (1891-1982) und Robert Anderson Cooke (1880-1960) in zwei unabhangigen Veroffentlichungen die Idee eines spezifischen Hausstauballergens bekanntgeben [11; 19]. Hausstaub laBt sich im Hauttest verhaltnismaBig Ieicht untersuchen. Manchmal reagieren Hausstauballergiker sowohl auf ihren eigenen Hausstaub als auch auf Staubproben aus anderen U3ndern mit einer starken Sofortreaktion [40]. In anderen Fallen ist das nicht der Fall [16].

Die 'Spezifischen' gewannen allmahlich an Boden. Unter Beri.icksichtigung der Postulate von Robert Koch (1843-1910) fur lnfektionskrankheiten begann die Suche nach .d.ftm Hausstauballergen, durch Storm van Leeuwen (1882-1933) als Klima-Allergen bezeichnet [37]. Die Liste der moglichen spezifischen Allergentrager wuchs bis auf 21 verschiedene Komponenten an, die 1942 in einem einzigen Versuch getestet wurden [2]. Auf ~ einzigartige Allergenquelle hat man sich erst in den Siebziger Jahren mehr oder weniger einigen konnen: Pyroglyphidae, Hausstaub-, oder Bettmilben [1;31;38]. Man bemi.ihte sich sehr, um das ganze Syndrom der Hausstaubmilbenallergie nur auf Pyroglyphidae zuruckzufi.ihren, obwoht Dissidenten, wie der Niederlander Professor Dr. Lubertus Barrens den Streit nicht aufgaben [2].

Obwohl der moderne Mensch sich bewuBt ist, in einer sich verandernden Welt zu Ieben, werden qualitative und quantitative, okologische und allergologische Verschiebungen bei Hausstaub und Hausstauballergenen im Laufe der Zeit selten diskutiert [4]. Vielleicht sind Mediziner und Techniker sich weniger der Tatsache bewuBt, daB die beste Beschreibung von biologischen oder okologischen Erscheinungen eine Sinus-kurve darst~llt [24], die meistens zyklische Schwankungen autweisen. Wenn wir aber die Anderungen in unserer Umwelt aufmerksam verfolgen, brauchen wir die wissenschaftlichen Daten keinesfalls falsch zu interpretieren.

MILBEN- UNO SCHIMMELPILZ-KARENZ ALS ALLERGIEBEHANDLUNG

lm praktischen Sinne nimmt die Empirie in der Verhi.itung allergischer Erkrankungen merklich zu. AmEnde der Zwanziger Jahre bringen Dekker !Solingen), Rost (Freiburg), Kremers (Amsterdam) un_!j Storm van Leeuwen (leiden) die Ergebnisse ihrer Untersuchungen in die Offentlichkeit. Das Konzept eines einzigen Hausstauballergens ist nicht einsetzbar. Asthma, Rhinitis und atopische Dermatitis kann mit einer Sensibilisierung und Betastung von verschiedenen lnnenraumallergenen verbunden sein, und mit spezifischen Karenz-MaBnahmen geheilt werden. Dekker geht soweit, daB er die Staubproben seiner Patienten auf Milben kontrollieren laBt bevor er eine Karenz­Empfehlung gibt.

Die am meisten abundanten lnnenraumallergene jener Zeit waren Milben (Acaridae und Glycyphagidae) und Schimmelpilze (Tabelle 1 ). Hausstaubmilben

61

Tabelle 1. Innenraumallergene in mehr als 314 der Wohnungen der Niederlande (van Bronswijk 1981, Kort personliche Mitteilung) [Nach 8/

Insekten Blattella germanica !,.epismatlaae · Psocoptera

Sliugetiere Cams familiaris Felis catus Mus musculus Rattus norvegicus

Mil ben Acaridae QlycyP.hagUf,ae PVrOglyphidae Tarsonemidae

Schimmelpilze Aspergillus glaucus Gruppe ASye!gillus restrictus Gruppe Ctadosporium Penicillium chrysogenum Serle Penicillium jrequentans Serie Phoma Wallemia

Deutsche Schabe - Silberfischchen

Staubliiuse

- Haushund Hauskatze

- Hausmaus - Wandetratte

- Vorratsmilben - Vorratsmilben - Hausstaubmilben - Schimmelpilzmilben

(Pyroglyphidae) kamen Oberwiegend in getrockneten Tierhauten und in Vogelnestern vor, und wurden einmal auf einer Zimmerpflanze gefangen [14;30].

Die Allergenkarenz wurde als wissenschaftlich unterstutzte und wirksamen Therapia anerkannt. Wohnungsmilben wie Acaridae und Glycyphagidae, und Schimmelpilze hatten eine groBe Verbreitung und Abundanz in den natGrlichen Materialien, die in Wohntextilien, wie Polstermobeln, Matratzen, Betten, und verschiedenen Typen Teppichen und Teppichboden Verwendung fanden. Manchmal konnte man sie auch auf Wanden aufspOren [1 0]. Das warder Fall unter sehr feuchten Bedingungen, als die Anzahlen in Wohntextilien hoch waren. Auf den Papiertapeten lebten die Milben von Schimmelpilzen [17;34].

Die Milbenkarenz der Zwanziger und DreiBiger Jahre zielte deshalb auf Vorratsmilben und die sie begleitenden Fungi. Die Entfernung kontaminierten Mobiliars, ein neuer Anstrich der Wande (keine Tapetal), lntensivreinigung und die Forderung des Luftwechsels mit frischer AuBenluft bildete zusammen den Karenz-Pian [12;26;34]. Empfohlen wurde auch Austrocknen durch konstante Erhitzung der Wohnung, wie der Entwurf und Bau allergenfreier Schlafzimmer und Bettkasten. Bautechniker und Mediziner kooperierten zu diesem Zweck.

Eine Hausstauballergie entsprach der Allergie fOr Acaridae, Glycyphagidae oder Fungi, in Abhangigkeit der vorhandenen Allergenaussetzung des Patienten. Es war nicht ungewohnlich, wenn im Hauttest 85% der allergischen Patienten fOr eine oder mehrere dieser Kleinlebewesen sensibilisiert waren. FOr ein

einziges lnnenraumallergen war kein Platz. Selbst die Idee der an spezifische Gegenden gebundenen Klima-AIIergene von Storm van Leeuwen kam mit der Praxis einer effektiven Haus-Sanierung nicht Oberein [25]. Vielleicht weil die Ereignisse dem Allgemeintrend der allergologischen Wissenschaft nicht entsprachen, sind die Resultate von Dekker und Kremers weitgehend vergessen worden.

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ANDERUNG DER WOHNUNGSAUSSTA TTUNG UNO DES WOHNVERHALTENS

Nach dem Zweiten Weltkrieg anderte sich die Art der Wohntextilien. In Europa fand ein langsamer Austausch von Pferdehaar, Stroh, Seegras und anderen FOIIungen pflanzlicher Herkunft statt, zuerst durch Kapok- und Baumwollfasern, ~pater durch Schaumgummi und Polyether. In Nordamerika setzten diese Anderungen frOher ein.

Der Prozentsatz menschlicher Hautschuppen im Hausstaub nahm zu. Der elektrische Staubsauger wurde allgemein benutzt, und erleichterte die Reinigung der Oberflache, nicht der tieferen Regionen der Heimtextilien. Dies war den Teppichwebereien und -kni.ipfereien der Siebziger und darauffolgenden Jahre wahl bekannt, die Teppiche entwickelten, in die der Schmutz schnell eindrang, so daB eine saubere Oberflache erhalten blieb. Die hygienische Bedeutung der so entstandenen Nischen fur pyroglyphide Milben war dieser lndustrie damals nicht bekannt [3;81.

Diese Bedingungen waren den Hausstaubmilben (Pyroglyphidael in Wohntextilien forderlich, was in den Niederlanden, Japan und Frankreich im Zeitraum 1962-1968 klar erkannt wurde [1 ;31 ;39]. Die Hausstauballergie der Sechziger und Siebziger Jahre erwies sich als eine Allergie auf pyroglyphide Milben. Es erschien nicht ungewohnlich, daB bei 85% der Allergiker einer bestimmten Gegend die Sensibilisierung gegen Dermatophagoides pteronyssinus, D. farinae oder D. microceras festgestellt wurde, obwohl in einigen Regionen Hautreaktionen zu Glycyphagus und Lepidoglyphus Arten in 29% bis 77% der Faile als positiv galten [9;15;32]. Die Patienten stammten sowoh[_von landlichen als stadtischen Gegenden.

Okologische Untersuchungen machten klar, daB das Zusammenleben von Pyroglyphidae und Fungi nicht so eng war wie im Fall der Vorratsmilben [5;13;28].

lnzwischen hat die Energiekrise von 1973 ihren Einflul?. ausgeubt. Das Wohnverhalten hat sich unter Einwirkung intensivster staatlicher Propaganda in die Richtung geringerer Ventilation geandert. In den Niederlanden wird eine luftwechselzahl von 1 Mal pro Stunde jetzt als zu hoch eingeschatzt [36].

UNGEZIEFER UNO BAUTECHNISCHE PROBLEME

Nachdem die meisten naturlichen Materialien im Wohnhaus nicht mehr vorkamen, die Staubsauger allgemein benutzt wurden, und genugend billige Energietrager zur Verfugung standen um das ganze Haus zu beheizen, tiel ein Befall von Acaridae und Glycyphagidae in die Domane der Kammerjager, die sich bis dahin fast ausschliel?.lich mit Parasiten wie Bettwanzen und Menschenflohen beschaftigt hatten. In den stadtischen Wohnhausern waren Plagen dieser Milben wirkliche Vorratsmilbenplagen geworden, da sie meistens von alten und verpilzten Vorraten wie Dosen Hundekuchen oder anderen Getreide-Produkten und nicht mehr von der Wohnungsstoffierung stammten. Die Bauern und ihre Familienmitglieder blieben ihnen in Stallen und Scheunen beruflich ausgesetzt.

Stand bei den Kammerjagern der Milbenbefall im Vordergrund, so waren die Bautechniker am meisten an Schimmelpilzen interessiert. Die Holzfaule war eine Bedrohung fur die Starke der Konstruktion, und die Pilzverschmutzung mineralischer Untergrunde war ein okonomisches Problem. Die Hauser bekamen einen niedrigeren Mietwert, weil sie als ungesund angesehen wurden [38].

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Das Schimmelpilzproblem vergroBerte sich, als Papiertapeten allgemein Gblich wurden (um den Zweiten Weltkrieg), und spater (in den Achtziger Jahren) als die Luftwechsel der lnnenraume wegen Energieersparnis nachlieBen. Mikroskopische Untersuchungen von Direktpraparaten schimmelpilzbefallener Oberflachen sind von Bautechnikern kaum unternommen worden, obwohl man die Pilzarten wohl kultiviert hatte. Erst 1989 ist festgestellt worden, daB auf diesen Pilzrasen normalerweise Vorratsmilben in groBen Mengen vorkommen [21 ;22].

Vergleicht man die heutige Situation mit derjenigen zwischen den Weltkriegen, so sind Wohnungsmilben der Familien Acaridae und Glycyphagidae nicht mehr die am meisten abundanten tierischen Bewohner von Wohnungstextilien, sondern von Wanden. Vorratsmilbenplagen kommen noch immer vor, ebenso die Vorratsmilbenbelastigung der landlichen Bevolkerung. Seit kurzem haben sich auch hier Verschiebungen durchgesetzt: Heu ist durch eingemietetes Gras, die Vorratsmilbenatopie ist moglicherweise durch eine allergische Alveolitis von Mikroorganismen ersetzt worden.

KGrzlich entdeckte die Medizin die Vorratsmilben zum zweiten Mal. Nicht nur unter der landlichen Bevolkerung, sondern auch bei den Stadtbewohnern ist der Sensibilisierungsgrad hoch [18;29].

MILBENKARENZ DER NEUNZIGER JAHRE

Unser Interesse ist es, nun nachzugehen, ob sich auf Karenzgebiet Anderungen im Laufe der Zeit ergeben haben.

Die Vielfalt der Arten von Milben im Wohn- und Arbeitsumfeld, neuerlich wieder Wohnungsmilben gen(!.nnt [33], erfordert eine eingehende Untersuchung der Taxonomie, Biologie und Okologie als Basis einer erfolgreichen Karenz.

Was die Karenz selbst anbelangt, scheint es, als ob wir den Daten der DreiBiger Jahre nichts neues hinzuzufGgen haben. Am Anfang steht noch immer eine ausfGhrliche Testung der Allgemeinaussetzungs-Palette (Tabelle 2): Nahrungsmittelallergene, lnneraumallergene und AuBenumfeldallergene. Wie Dekker 1928-1930 untersucht man aufs neue die Staubproben von Patienten­wohnungen (diesmal mit dem ACAREX-Test). bevor man einen Karenz-Pian aufstellt. Auch der lnhalt des Sanierungsplans kommt weitgehend mit dem von Dekker und Kremers Gberein: Austrocknen, Spezialreinigung, erneute Aus­stattung und nur ein Anstrich der Wande [7;20;23]. Eine multidisziplinare Zusammenarbeit von Medizinern, Technikern und Biologen beginnt aufs neue.

Tabelle 2. Der Karenzylan for Allergenquellen und Allergenreservoire

a ANAMNESE I DIAGNOSTIK

a-1 Nahrungsmittelallergene (Eier/ Fisch/ Erdniisse/ Friichte) a-2 lnnenraiimallergene (Miloen I Schimmelpilze/ Haustieref Ratten/ Mause/ Schaben) a-3 AuBenumfeldallergene (Baumpollen I Graspollen)

b 1m Faile einer klinisch relevanten Sensibilisierung fiir Innenraumallergene ist eine WOHNUNGSSANIERUNG notwendig:

b-1 Detektion der relevanten Allergenreservoire (Staubproben) b-2 Vertilgung der Quelle oder Entfemung (Bioude OOerfliichenbehandlung) b-3 Reinigup.g der Reservoire (Staub8augen l Waschen) b-4 Priivention (Feuchtereduzierung I Matratzenumhiillungen) b-5 Allergeniiberwachung ( = b-1 einmal his zweimal pro Jalir)

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Untersuchungen am Ende der Achtziger und in den Neunziger Jahren machten wiederum klar, daB nur ein individueller Karenz-Pian unter der standigen Anleitung von Experten bei der AusfOhrung der Sanierung einen konstanten Erfolg hat. lm Sinne der zuvor genannten Sinuskurve der naturlichen Erscheinungen ist jetzt ein kompletter Zyklus beendet.

ZUM SCHLUB

Milben der Familien Acaridae und Glycyphagidae, heutzutage Vorratsmilben genannt, und vor 60 Jahren als Wohnungsmilben bezeichnet, sind fOr Kammerjager, Bautechniker und Biologen immer aktuell geblieben. Zwischen dem Ende des Zweiten Weltkrieges bis zur allgemeinen EinfOhrung der EnergiesparmaBnahmen als Folge der Energiekrise (1973) sank die allergologische Bedeutung von Acaridae und Glycyphagidae in der stadtischen Wohnung ab, um in den letzten 1 0 Jahren wieder anzusteigen.

In der Wohnung haben sich die von diesen Milben besetzten Nischen weitgehend geandert. Von Bewohnern der Wohnungstextilien und Wande sind sie nur noch auf dem Schimmelpilzrasen der feuchten Wandoberflache heimisch. Mit der Verringerung der Luftwechselzahl hat sich die Feuchte der Raumluft und der Oberflachen in den Hausern Westeuropas erhoht, somit neue Moglichkeiten fUr die Wohnungsmilben der DreiBiger Jahre schaffend. Bis jetzt bleiben die pyroglyphiden Milben die bedeutendste Gruppe in den Wohnungstextilien.

Was die Kreuzallergenitat zwischen Milben, Schimmelpilzen und Hausstaub anbelangt, hoffen wir deutlich gemacht zu haben, daB dies von den okologischen Bedingungen innerhalb der Wohnung abhangt. In Westeuropa gab es immer einen Zusammenhang zwischen Hausstaub und Wohnungsmilben. Nicht die ldentifikation ger Milben in den vergangenen Jahren war falsch, sondern die Haushalts-Okosysteme haben sich im Laufe der Zeit geandert.

lmmer wenn Acaridae, Glycyphagidae oder Tarsonemidae im Spiel sind, haben auch die Schimmelpilze, fUr die Milben als Futter und Nische, fur den Patienten als zusatzliche Allergenquelle eine groBe Bedeutung.

Hausstauballergie in Westeuropa ist eine Kombination von Sensibilisierungen fur lnnenraumallergene. Karenz-Programme sollten sich nach der individuellen Allergen-Aussetzung richten und sowohl klinisch relevante Quellen als auch Reservoire einschlieBen. Als AllgemeinmaBnahme ist wie fruher die ErhOhung der luftwechselzahl mit frischer AuBenluft zu empfehlen. Erstens um den Gehalt an Raumluftverschmutzungen zu verringern, zweitens um die Wohnung trocken zu halten. Die Vorratsmilbenaussetzung in Bauernhausern wird im Zusammenhang mit landwirtschaftlichen Erneuerungen abnehmen.

Kehren wir nach Hansen und seinen Kollegen in ihrer multidisziplinaren Behandlung des Problems durch A.rzte, Techniker und Biologen zuruck. Was Allergen-Karenz anbelangt, ist immer noch viel von den alten Meistern zu lernen.

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[351 Schadewaldt, H. (1980). Geschichte der Allergie. Dustri-Verlag, Dr. Karl Feistle MOnchen-Deisenhofen. Band 2: 207-208.

[36] Schober, G. (1991). Control of allergenic mites and fungi in house dust. Ph.D. thesis, Utrecht, the Netherlands. 179 pp.

[37] Storm van Leeuwen, W. (1929). Ueber die Spezifitat der Allergen­reaktionen. Zeitschr. lmmuniti:itsforschung 62: 360-389.

[38] Varekamp, H. (1963). De invloed van klimaat en behuizing op huisstof­allergie. Ned Tijdschr Geneeskd 107: 227-229.

[39] Voorhorst, R., Spieksma-Boezeman, M.f.A., Spieksma F.Th.M. (1964). Is a mite (Dermatophagoides sp.) the producer of the house-dust allergen? Allergie und Asthma 1 0: 329-334.

[40] Voorhorst, R. & Spieksma F.Th.M. (1978). FGnfzehn Jahre Hausstaub­milben-Forschung in Leiden. Allergologie 2: 93-101.

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CHAPTER Ill HEALTH DAMAGE

111.2 CLINICAL IMPROVEMENT AFTER UNUSUAL AVOIDANCE MEASURES IN THE HOME OF AN ATOPIC DERMATITIS PATIENT, A CASE REPORT (published in Allergy t 993; 48: 468-471)

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Allergy 1993:48:468-471 Primed in Belgiwn ull righu reserved

ISSN 0105-4538

Case report

Clinical improvement after unusual avoidance measures in the home of an atopic dermatitis patient

Kort HSM, Koers WJ, van Nes AMT, YoungE, Vorenkamp J, Wolfs BG, van Bronswijk JEMH. Clinical improvement after unusual avoidance measures in the home of an atopic dermatitis patient. Allergy 1993: 48: 468-471. © Munksgaard 1993.

H. S.M. Kort, W. J. Koers, A.M. T. van Nes, E. Young, J. Vorenkamp, B. G. Wolfs, J. E. M. H. van Brooswijk Interuniversity Task Group "Home and Health", Utrecht State University Medical School. and Technical University Eindhoven, The Netherlands

A 27 -year-old female office clerk with widespread atopic dermatitis (AD) since infancy appeared to be highly sensitized and exposed to molds, storage mites, and chicken feathers and moderately sensitized to house-dust mites and grass and birch pollens. Hardly any textiles were present in her home; that is, only 28 m2, which is less than 25 ~;. of the Dutch national average. The causal relationship between eczema and molds plus storage mites in this case of AD was strengthened by the positive effect of an unusual, multidisciplinary home-sanitation program involving cleaning of mineral surfaces and ventilation improvement. This home-sanitation program Jed to a gradual drop of total IgE and clinical symptom scores to 21 ~o and

Key words: atopic dermatitis; home sanitation; mites; molds.

13%, respectively, of the original values.

In the pathogenesis of atopic dermatitis (AD), ge­netic influences play a role together with environ­mental factors. The clinical effect of house-dust al­lergen avoidance by cleaning or removal of textiles from the home has been reported repeatedly since 1929 (2, 5, 6). As was stated recently, the numbers of viable fungi in floor coverings are weakly associ­ated with allergic symptoms (9).

We report on an association between eczema symptoms and exposure to fungi and mold-devouring mites living on walls and room partitions in a chronic case of AD.

Material and methods Patient

A 27-year-old woman office clerk with widespread AD since infancy had attended the outpatient clinic for over 1 year. Symptomatic therapy did not im­prove her dennatologic and respiratory symptoms. Since her symptoms became exacerbated, she was admitted to hospital from 7 February until 12 M~y

Accepted for publication 18 December 1992

1989 (University Department of Dermatology and Allergy, Utrecht, the Netherlands).

The patient appeared to be highly sensitized to a mold mixture, storage mites (SM), and chicken feathers (skin test score > 2); moderately sensitized to house-dust mites (HOM) and grass and birch pollens (score 2); and slightly sensitized to several foods (score 1) (on the scale 0-4). Her total serum IgE concentration was 24000 kU/1 before hospital­ization. The intensity and the topography of the AD was scored at admission to the hospital and after 3.5 years, according to a simple scoring system (3). Spe­cific IgE was measured by RAST and after 1989 by the Pharmacia Cap system RAST FEIA (Pharma­cia, Uppsala, Sweden). Therefore, specific IgE re­sults are given in RAST classes. Total serum IgE was measured by RAST, but after 1989 the Phar­macia CAP system IgE FEIA was used (Pharmacia, Uppsala, Sweden).

Eczema around the eyes, conjunctivitis, and res­piratory symptoms prevented the patient from read­ing and performing other office functions. In addi-

71

tion, she felt chronically tired and had to give up her favorite sports. During hospitalization, an antiec­zema treatment (wood tars and local corticoster­oids) was given together with a wheat-, egg-, nut-, and fruit-free diet. Topical therapy could gradually be diminished. Her diet included fruits and wheat again. During weekend leaves, symptoms became exacerbated, especially after the patient had been in the kitchen, although there were no textiles in that room.

The patient's home environment

The patient's home had been built around 1780 and was adapted to modern living without the massive introduction of textiles. There were only one couch, a double bed, one padded chair (in total 12 m2 area), and 16m2 textile floor covering in the whole house. Average textile area per home in the Netherlands includes 63 m2 surface of padded furniture and 52 m2

textile floor covering ( 4 ). Allergen exposure appeared mainly to originate

from walls infested with mites and molds (total in­fested surface about 400m2

). On the mineral sur­faces, molds were more widespread than domestic mites. Penetrating- and rising-damp areas were dis­covered, especially in the bedroom, as welt as insuf­ficient ventilation and a high level of relative humid­ity in the kitthen. In March 1992, relative humidity and temperature were measured for 1 week with a Vaisalta reader (Helsinki, Finland) to establish the home's (Dutch) indoor climate class. By this method the humidity of dwellings may be evaluated (7).

Allergologic inventory

An allergologic survey of the patient's home was performed twice in April1989. Airborne mold spores were collected in all rooms for 15 min by the open Petri dish method (Oxoid malt with a water activity of0.99). Dishes of69.4 cm2 were incubated at room temperature for 2 weeks before analysis. Adhesive tape samples were taken from walls. Walls, floors, and textiles were vacuumed (1 min/m2

), and the col­lected dust was analyzed for mites by a flotation method.

Short-term management

A causal, preventive therapy was tried as follows: I) removal of the highly mold-infested couch and

bedroom carpet (16m2)

2) special cleaning twice a year with a) Apesin AP-100 (R) (Mg-monoperoxyphthalate-hexahydrate) (Werner & Mertz, Mainz, Germany) to kill fungi and remove mites on walls and ceilings; b) Aca­rosan (R) (benzylbenzoate) (Werner & Mertz,

72

Clinical improvement after unusual allergen avoidance

Mainz, Germany) to kill mites and remove their allergens on the remaining padded chair

3) machine washing at 60 o C or dry cleaning of clothing (once)

4) purchase of two washable mattresses (Lava­Dorm) (Waidner & Co., Freiburg, Germany) which were washed four times yearly together with pillows and quilt

5) mowing the lawn more frequently to prevent flow­ering of grass

6) removal of the henhouse in the garden (although the patient was hardly exposed to it).

At the patient's workplace, similar procedures were followed after November 1989. Textiles were first cleaned with acaricidal detergents, but were later replaced by furniture with nontextile covers.

Long-term management

For a long-lasting reduction of fungi and mites, moisture levels had to be diminished. A 24-h heat­ing and ventilation scheme was prepared for the dwelling. Measures taken included the following: !) The outside front wall was made hydrophobic. 2) Ventilation grilles were installed in the kitchen,

the attached scullery and built-on shed were de­molished, and an extra door was constructed.

3) Mechanical ventilation was installed in the bath­room.

4) Wall-lathing was removed in the bedroom tore­duce empty spaces inhabitable by molds and mites.

5) The roof was paneled, and the attic floor and walls were covered with thermal insulation ma­terial.

6) Gutters were replaced and leaks repaired. 7) Acetate-containing sealant was avoided, since it

is prone to fungal attack. 8) Finishing was renewed with nonhygroscopic ma-

terials. During these alterations (November 1989 to March 1990), the patient lived in a trailer to avoid exposure to the dust of construction work.

All cleaning procedures were performed by the patient's husband and other relatives. This home­sanitation plan was supervised by a team of physi­cians, engineers, and biologists, who visited the home six times altogether.

Results

The allergologic survey of the dwelling revealed var­ious mold and mite species and other arthropod species. Per gram mattress dust were found 150 tar­sonemids and eight SM (both fungus-eating types of mites), 36 HOM, and six other acarids (6m2

; 0.25 g dust collected). Bedroom walls (160m2

; 1 g dust

Kort eta!.

collected/20m2) were inhabited by molds (Aspergil­

lus. Penicillium. Cladosporium; about 40000 spores/ cm2

), HDM (mean 11.8/g dust), SM (mean 15.4/g), oribatids (mean 7.1/g), and dust lice (mean 16.9/g). SM species found belonged to the genera Tyropha­gus, Acarus, and G/ycyphagus. A mean of21.3 mold­colony-forming units (cfu)/air-exposed dish was found. After the avoidance measures were taken, three HDM, three oribatids, 10 dust lice, and three plant lice were found per gram in dust from the washable mattresses, pillows, and bedding (21 m2

;

1.2 g dust collected). One week after the first cleaning, the number of

viable diaspores had dropped to a mean of 6.5 cfu/ dish. Six weeks after the first cleaning, this had again risen to a mean of 15.3 cfu/dish. Mold- and mite­infested textiles had just been removed. Fifteen weeks after the first allergologic cleaning, viable fun­gal spores had increased to a mean of 66.2 cfujdish. By this time, construction work had started and caused an increase in airborne dust and molds. Five months after the fifth cleaning in November 1991, the mold spores had decreased to a mean of 8 cfu/ dish.

After 3 years of humidity management, the house was classified as (Dutch) indoor climate class II, a normally dry home, while at the start of the study it was assigned to class IV because of surface conden­sation and mold growth on the inner walls.

Total serum IgE concentration was 24000 kU/1 before hospitalization, dropping to 15000 kU/1 dur­ing hospitalization (Table 1). In April 1989, the pa-

Table 1. TotallgE corn:emratioo and specific lg!: values lor HOM and SM diNing 4 years. Specif~ lg!: is given in RAST classes; totallg!: as kU/1

HOM RAST Date class

7·87 nd 2-88 6 3·88 4 2·89 nd 3-89 nd 4-89 5·89

6-89 2·90 5·90 2·91

11·91 4-92

10·92

SM RAST class

nd nd nd nd nd

6 nd nd 2

nd 131*

1121*

TotallgE in kU/1

27000 23500 24000 21000 15000

18500

12000 9300 9100 6366 6204

4407

Actions tal<en

Hospitalization Weekend leaves Allergologic survey Discharge from hospital and 1st allergologic claaning

2nd allergologic cleaning 3nl allergologic cleaning 4th allergologic cleaning 5th ~lergologic cleaning 6th alk!lgologic cleaning

During construction W<llk Novembe! 1989-Maroh 1990, pa!iertt stay«! in a tent trailer to avoid exposure. HOM: Oermatophagoides fileronyssi!ws. SM: Tyrophagus putrescentiae. 1 r Another stolage mite: Glycyphagus rJomesticvs. nd: not done.

tient's total serum IgE concentration increased to 18500 kU/1 after weekend leaves. After the first al­lergologic cleaning in May 1989, it was 12000 kU/ I. Constructional improvements and residence in the trailer ended in March 1990. By this time a decrease to 9100 kU/1 had taken place. After the fourth aller­gologic cleaning in February 1991, total serum IgE concentration dropped further to 6366 kU/1. A con­tinued reduction in total IgE was seen until October 1992, when the concentration was 4407 kU/1. This was a reduction of 80% from the initial concentra­tion (Table 1).

Scoring of the patient's AD in intensity and to­pography decreased from 78 (whole body and face affected) at admission to hospital to 10 (involvement of only the ventral site of the trunk and dorsal site of the upper arm) after 3.5 years of avoidance mea­sures (maximum score= 100). Although no dramatic changes in specific IgE have been seen (Table 1), skin prick tests suggest a decreased sensitization to SM and an increased sensitization to HDM and pollen. No change in skin prick tests for molds has been seen (Table 2).

In November 1989, the patient resumed work. Nowadays she still follows a limited elimination diet, and her dermatologic medication has been reduced to an occasional use of wood tar on the face. Res­piratory symptoms .have disappeared. The patient cycles 30 km a day with pleasure.

Table 2. Results of skin prick tests expressed as wheal diameter bel011l and during hospitalization. and alter avoidance measures in the itoml!

After Befure During avoidance

Antigen source hospitalization hospitalization measures

DermaiDphagoide pterooyssinus 2 M 4 Acarus silo nd 1'/z 0 T yrophagus puuescentiae od 2'/' 1 Lepidoglyphus destructor nd 2 0 Aspergillus nd 1'/z 2 Penicillium nd 2 2 Alternaria/Cladosporium rul 3 2 Mold mixture IV nd 3'1> 3 Mold mixture V nd 3 2 Basidiomycetes nd 1'/z 1'{2 Grass pollen 2 nd 3 Tree pollen 1'/• nd 3

Skin test 1 =wheal of 5 mm in diameter with erythema loccording to Voorhorst et at .. 1969)8

.

Sl<in tests done with Dermatophagoides pterooyssinus. mold allergens. and grass and ttae pollens are from HAL alergenen laboratorium BV, Haarlem, the Netherlands. Skin tests done with SM allergens are from Oiephuis, Groningen, the Netherlands. Mold mixl1Jre IV= M/JCOf mucedo, llhizopus nigricans, Aureobasidium pulfulans. Canrfllla a/bicans. Mold mixture V = Sl8mphr/ium botryosum, Botrytis dnera, Fusarium cufmorum, Tricho· derma viride, Phoma betea, Helminthospurium halodes nd: not done.

73

Discussion AD is a multifactorial disease. Factors such as in­door climate and allergens have an effect on the skin (2). The patient's damp home harbored allergens originating from walls infested with molds and mold­devouring mites. The few mite-infested textiles in the home were removed at the beginning of the study.

The patient's total serum IgE concentration dropped after hospitalization, and a further decrease was seen after residence in the trailer. This agrees with other studies (5, 6) and could be expected, since in hospital and in the trailer no exposure to molds and mites occurred. Relocation to another environ­ment was temporarily successful, because after the patient returned to the damp home for weekend leaves and was exposed to molds and mites living mainly on the inner walls, her symptoms worsened. A total relapse was prevented by the execution of a multidisciplinary home-sanitation program. Inten­sive fungicidal and acaricidal cleaning led to a de­crease of mold diaspores in the air and mite numbers on the walls. However, when only cleaning was per­formed, mold exposure increased within 3 months. A long-term effect was achieved by humidity man­agement. The decrease in total lgE continued, and the clinical symptom score diminished.

This case study shows that exposure to molds and mites living on home walls may play a role in atopic diseases such as AD. Previously, no relation was found between the amount offioor-dust-bound fungi and atopic diseases, probably because only textiles in the home were intensively cleaned while exposure to molds from walls remained (9). Recently, cat and mite allergens have also been isolated from home inner walls (10).

This is the first report of a successful, multidisci­plinary home-sanitation program aimed mainly at the allergenicity of mineral surfaces. Other reports have dealt with avoidance of mite allergens from textiles (1, 5) or relocation or residents to "minirisk" houses (2).

74

Clinical improvement after unusual allergen avoidance

We conclude that allergen avoidance in damp homes of AD patients may have to follow unusual paths to be successful. This type of allergen survey and planned home treatment should be repeated in other homes to achieve more generally applicable results.

Acknowledgments We thank the Sticbting Minibiologisch Onderzoek, the Nether· lands, and the Gesellschaft far hausbioiogische Forschung mbH (Mainz, Germany) for financial support, and Mr J. Scharringa for technical assistance.

References 1. AUGUST P J. House dust mite causes atopic eczema. A pre­

liminary study. Br J Dermatol 1984: Ill (Suppl. 26): 10-11. 2. BECK H, BJERR!NG P, HARVING H. Atopic dermatitis and

the indoor climate. The effect from preventive measures. Acta Derm Venereol (Stockh) 1989: 69: 162-5.

3. COSTA C, RtLLIET A, NICOLET M, SAURAT JH. Scoring atopic dermatitis: the simpler the better. Acta Derm Venereol (Stockh) 1989: 69: 41-5.

4. KNIEST FM, WoLFS BJ, Vos H, eta!. Mechanisms and patient compliance of dust-mite avoidance regimens in dwell­ings of mite-allergic rhinitic patients. Clin Exp Allergy 1992: 22: 6Bl-9.

5. PLA rrs-MILLS T AE, MITCHELL EB, ROWNTREE S. CHAP· MAN MD, WtLKI:'IS SR. The role of dust mite allergens in atopic dermatitis. Clin Exp Dermatol 1983: 8: 233-43.

6. Rosr GA. Ober Erfahrungen mit der allergenfreien Kammer nach Strom van Leeuwen; inbesondere in der Spatperiode der exsudativen Diathese. Arch Dermatol (Berlin) 1929: 155 (Suppl.): 297-304.

7. TAMMES E, Vos BH. Warmte· en vochttransport in bouw­constructies. Deventer: Kluwer, 1983.

8. VooRHORST R, SPJEKSMA FT, V ARENKAMP H. House dust atopy and the house dust mite. Leiden: Stalleu, 1969.

9. WICKMAN M. GRAVESEN s, NORDVALL SL, PERSHAGEN G, SUNDELL J. Indoor viable dust-bound microfungi in re­lation to residential characteristics, living habits, and symp­toms in atopic and control children. J Allergy Clin Immunol 1992: 89: 752-9.

10. WooD RA, MUDD KE, EGGLESTON PA. The distribution of cat and dust mite allergens on wall surfaces. J Allergy Clin lmmunol 1992: 89: 126-30.

CHAPTER Ill HEALTH DAMAGE

111.3 CLINICAL AND TECHNICAL EFFICACY OF MITE AVOIDANCE MEASURES IN 3 ATOPIC DERMATITIS CASES (to be published in an international biomedical journal)

75

76

CLINICAl AND TECHNICAl EFFICACY OF MITE AVOIDANCE MEASURES IN 3 ATOPIC DERMATITIS CASES

HSM Kort, F de Maat-Bieeker, BG Wolfs, E Young, JEMH van Bronswijk Interuniversity Task Group "Home and Health", Utrecht State University and Eindhoven University of Technology, the Netherlands.

ABSTRACT

Patients with atopic dermatitis were selected for an avoidance study. The patients showed multiple sensitizations for indoor allergens and their allergy was clinically expressed as atopic dermatitis with additional symptoms of rhino­conjunctivitis or asthma. The eczema as scored by the physician amounted at the start of the trial for patient 1 ('¥; 29 years old), to 77 for severity and 4 for extensiveness. For patient 2 (o; 19 years old) these scores were 345 and 35 respectively. The eczema of the brother of patient 2, patient 3 (o; 15 years old), was judged by the physician at 207 for severity and 5 for extensiveness. Maximal severity value = 945 and maximal extensiveness value = 45.

Allergological sanitation aimed at avoidance of house dust mites (Pyroglyphidae), storage mites (Acaridae, Glycyphagidael and fungi. The patients lived in houses with a (Dutch) indoor climate class 11/111 (Water-vapour difference between indoors and outdoors of 450 Pa at 2 ° C outdoor temperature).

In dust samples mite numbers were counted, and guanine amount was assessed semi-quantitatively. Dust quantity and guanine amount figures were used to calculate dust and guanine exposure. After establishing an exposure inventory, an avoidance plan was formulated and executed. This included acaricidal cleaning, normal cleaning procedures, the introduction of washable beddings and encasing of mattresses. During the trial, symptoms were scored by patient and physician. Read-outs for clinical parameters (skin-tests and blood eosinophils) were done eight times in a 1 ~ year period. Total and specific lgE were determined three times. Dust samples were taken five times in a 1 ~-year period from all home-textiles and from all walls. In addition some walls were sampled with adhesive-tape.

Use of new washable duvets and pillows, and mattress covers did not prevent colonisation of the cover surface by mites, but guanine amount stayed beneath the no-sensitization risk level. Acaricidal treatments of floor-textiles were only successful in the case of heavily infested floors.

The severity of eczema symptoms as scored by patients, decreased significantly in patient 1 & 2 after avoidance measures had been taken. On the other hand, the extensiveness of the eczema decreased only in patient 2. Severity symptoms as judged by the physician decreased in patients 2 & 3 to 33% and to 10% of the initial value respectively. The physician, however, did not score a decrease in the extensiveness of the skin disease in any of the patients.

The avoidance measures executed were technically effective in reducing mite exposure, but a significant clinical benefit was obtained only in the case of severe atopic dermatitis (patient 2). In moderate cases of atopic dermatitis management of indoor humidity should follow after short-term allergen avoidance procedures. Besides this, individual threshold levels for mite exposure seem to differ.

77

INTRODUCTION

In the Netherlands about 2.5% of the population suffers from atopic dermatitis [1 ]. Atopic dermatitis patients often have allergic asthma or rhinitis too [2]. Mite exposure causes sensitization to mites and later on development of symptoms such as allergic asthma, rhinitis or atopic dermatitis [3]. To achieve a reduction in mite exposure, mite avoidance measures are applied in the houses of atopic patients in order to reduce allergic symptoms.

Mite avoidance measures include barrier measures, such as use of mattress encasings, application of acaricides, relocation or hospitalization of patients, or humidity management. In laboratory experiments the efficacy of these procedures in reducing mite exposure are examined separately. Efficacy of mite allergen avoidance measures is determined by mite counts, assessment of guanine amount or allergen concentration. The effect of allergen avoidance in reducing clinical symptoms is often given by total lgE, specific lgE, skin tests, medication use and symptom scores [3;4;5].

Several studies revealed that mite avoidance results in clinical improve­ment of atopic dermatitis patients, while others found no effect. In mite avoidance trials, reduction in mite exposure is not always achieved. In some avoidance studies, mite reduction was not monitored, though clinical improvement was achieved, obscuring the possible effects of measures taken [reviewed in 4].

Therefore, in this study, we made a distinction between technical efficacy of mite avoidance measures in reducing mite exposure, and efficacy of the avoidance programme in reducing clinical symptoms, in order to know to what extent mite avoidance measures are successful in improving atopic dermatitis skin lesions.

SUBJECTS AND METHODS

Subjects Five subjects attending the allergy outpatient clinic of the University Hospital of Utrecht, the Netherlands, were initially selected. Patients were included on the basis of the following criteria: suffering from atopic dermatitis according to the criteria of Hanifin and Rajka [6], with or without asthma or rhinitis, and a sensitization to domestic mites. Sensitization to domestic animals and food were acceptable, only when patients were not currently exposed. In the home at least one, or preferably more textile objects should have an Acarex !AIIergopharma Joachim Ganzer KG, Reinbek, Germany) value greater than 1 + (;;:: 0.6 mg guanine I g dust).

Patients selected consisted of three men {aged 15, 19 and 25 year) and two women (aged 26 and 29 year). During the trial the male patient of 25 years and the female patient of 26 years of age were withdrawn, because they moved to an other house. We will only report on the 3 remaining patients.

Home environment The study was completed in two houses that were located in Enkhuizen and in Zeist, both sub-urban Dutch environments. The house in Enkhuizen was inhabited by a 29 year-old female patient with atopic dermatitis (patient 1 ), her spouse and their three children who were between 4 and 8 years old. In the house in Zeist, two brothers 15 and 19 years old (patient 3 & 2), suffering from atopic dermatitis, were living with their parents.

78

The houses in Enkhuizen and Zeist were built in 1984 and 1980 respectively. Both homes have a central heating system (hot water) and are one-family houses. The houses were already sanitated conventionally [7] before the trial started. In Enkhuizen, the living room and one of the bedrooms had a non-textile floor covering. The patient's bedroom was furnished with wall to wall carpeting. In Zeist, all bedrooms and the living room had non-textile floor covering. In the living room two carpets were present on the non-textile floor.

During one month in the heating season (November - December 1991 I relative humidity and temperature were measured in the houses with a thermo­hygrograph, to establish their (Dutch) indoor climate class (8]. Classification was done as described by Kniest et al [9].

Study protocol Subjects were examined eight times by a physician; six weeks before allergological inventory of indoor allergens (August 1990), and after 5, 8, 11, 13, 16, 17, and 18 months (March 1992). At each visit, absolute blood eosinophils were assessed, and the extensiveness and the severity of the atopic dermatitis were scored by the physician. The scoring system was based on Costa et al [5) with the introduction of a slight modification in the severity criteria as following.

The severity of atopic dermatitis was scored for each body part by 9 criteria (erythema, papules, vesicles, crusts, excoriations, scales, lichenification, oedema, pruritus) from 0 to 7 (maximal severity value = 945 for the whole body). Extensiveness scores were graded from 0 to 3. All symmetric body parts, face, head, buttocks, ventral and dorsal side of the trunk were included. In total 15 body parts were inspected (maximal extensiveness value = 45). Medication use was also charted.

Six weeks before allergological inventory, and after 13, and 18 months, total and specific serum lgE value were determined with the Pharmacia CAP system lgE FEIA (Pharmacia, Uppsala, Sweden). An intracutaneous skin test was carried out with Dermatophagoides pteronyssinus (Diephuis/ALK), a mixture of the storage mites Lepidoglyphus destructor, Tyrophagus putrescentiae and Acarus siro (Diephuis/ALK), cat (HAL), dog (HAL), mouse (HAL), rat (HAL), guinea-pig (HAL), mould mixture of Aspergillus fumigatus, Penicillium notatum, Cladosporium cladosporioides, Alternaria Altemata and Mucor mucedo (HAL), Pityrosporum (HAL), a mixture of birch pollen, hazel pollen, alder pollen (HAL), Artemisia pollen (HAL), grass pollen I (HAL), egg white (Diephuis/ALK), peanut IDiephuis/ALK) and, fish (Diephuis/Aik). Histamine (HAL) and controls (HAL) were included.

The sensitization pattern of the patients at the start, and at the end of the study, is given in table 1 .

On a weekly basis, severity was scored on a scale from 0 to 4. Symptoms scored included itching and dry skin, as well as the following rhinitis I asthmatic complaints: nose secretion or sneezing, tightness of the chest, and eye irritation. Sleeplessness as well as exposure to animals or pollen were noted on a scale from 0 to 1. Maximal severity score (eczema and rhinitis I asthma) being 23. The extensiveness of the atopic dermatitis from 15 body parts was scored in a grade from 0 to 1 for each body part (max = 15 for the whole body).

Dust samples were taken from all home-textiles and all inner walls and room partitions, with a Hoover S 2222 (550 W, Hayesgate, UK) by vacuuming the whole surface with an intensity of one minute per square meter. Dust collected from walls was investigated as described by Kort [9]. Adhesive-tape

79

samples were taken as described previously [10], from all inner walls and room partitions with visible mould growth. Additionally some walls without visible mould growth were taped too.

Dust and adhesive-tape samples were taken five times within a 1 %-year time period; September 1990 (TO}, January 1991 (T1), May 1991 (T2), October 1991 (T3) and January 1992 (T4).

Mite avoidance measures Washable duvets and pillows (Morpheus, Brinkhaus GmbH & Co. KG, Warendorf, Germany) were purchased between T1 and T2. Both families received a scoring list every month to score the frequency of washing and write their remarks.

Mattress-encasings (Mitecare·; a cotton-polyester fabric coated with polyurethane; Artu Biologicals, Lelystad, the Netherlands) were also supplied between T1 and T2. In Zeist the mattresses of patient 2 and 3 were replaced by new ones in February 1991.

Table 1. Sensiti<ptwn of patients. S results m plus srgns accor; Blood eosmophi/S are per

de1wted in ronwn numerals. Skin-test . Total IgE levels are given in kU!l. are giVen

Test results

Patient 1 Patient 2 Patient 3

Allergen sources Initial End Initial End Initial End value value value value value value

Detmatophagoides ptm:myssinus II Ill VI ~·h+) I ~~+> nd (2+) (l'h +) (3+) (31h+)

'8Jro 'ae nd 0 nd IV nd nd us nd 0 nd III nd nd

st6 es (nd) (-) (21h) (l+) (2+) (2+)

Asper§illqs f:::iatus I II nd III nd nd Moul IIl1X * (1 +) (1+) (2+) (1 +) (-) (Ph+)

Birch pqllen nd 0 VI v III nd Tree P.Ollen***

~~ &-) ff+> frh) p+> (3 1h) Artemisia pollen nd

(- (-) (nd) (l+) (-) (2+)

~r~il~ltep* nd I VI v VI nd (-) ('h+) (3+) (21h+) (3+) (3+)

Egg-white nd I III III II nd (nd) &nd) Vt> Vr+) {it ~J Peanut nd

Fish (nd) bnd) fw> \J'h+) p+> (2+) lid II nd (nd) (nd) (3+) (nd) (2'h+) (2+)

Histamine***** (2+) (Ph+) (Ph+) (l+) (2+) (Ph+)

Control (-) (-) (-) (-) (-) (-)

Total IgE 907 17200 6429 2180 nd

Blood eosinophils 143 600 198 275 330

'l!tlent 1 + t-', years); nd = not done.

{l years; rauen " = o (l' years), brother or patient 2.

• Storage mi,tes mixture of Lepidoglvvhus desfrJlctor, Tyrophagus putrescentiae and Acarus siro. •* MoUld IIllXture of Alternarta and' CladosPOrium spec. *•• Tree pollen mixture of birch hazel and' alder. *•*• Grass pollen mixture I (HAL), which includes rye-grass. *•**• Histamine skin test were done in a dilution of 1 : 100,000.

80

Home textiles were treated twice a year with an acaricidal cleaner at T1 and T3. We used Acarosan foam (AIIergopharma Joachim Ganzer KG, Reinbek, Germany) to treat upholstery, cuddly toys, and mattresses. Acarosan powder was used to treat carpeting and rugs. Treatments were performed as prescribed by the manufacturer.

Dwelling inner walls and room partitions were vacuumed only. In the case of visible mould growth, the inhabitants were advised to clean the walls with active oxygen bleach, diluted ten times, and to remove the fungal growth.

Analysis Dust samples were weighed and analyzed for mite numbers by use of the flotation technique of van Bronswijk [12]. Guanine was assessed semi-quanti­tatively by use of Acarex (AIIergopharma Joachim Ganzer KG, Reinbek, Germany). Acarex values were converted to guanine amount per gram dust (mean values) according to Bischoff & Schirmacher [13]. Guanine and dust exposure were calculated as described by Kniest et al [7].

Adhesive-tape samples (Scotch Magic 810 3M, Cergy pontoise, France) were examined by direct-light microscopy for fungi and arthropods, and inoculated on agar plates prior to identification as described in [10].

Clinical symptoms scored by the patients were evaluated as follows: the median value of a six-week period were used. If less than 3 weeks were scored, the median of the previous period was taken. For the evaluation of medication use, a distinction was made between preparations containing corticosteroids, those containing wood-tar, and daily-care preparations. The corticosteroid preparations were divided into four different classes of strength [14].

Data on symptom scores, guanine exposure, and dust exposure were normalized by dividing them by the initial values. The sign test was used with these normalized data to compare scores of patient and physician. Changes in guanine and dust exposure, on the one hand, were compared in the same way with the severity and the extensiveness of the eczema and rhinitis asthmatic symptoms on the other. The sign test was also used to compare skin test and specific lgE values at the start and at the end of the study. The Mann-Whitney U-test was used with non-normalized data to assess differences in total mite numbers per gram, guanine and dust exposure, and symptom scores before and after avoidance measures. The periods TO and T1 were taken as the period before avoidance measures and T2, T3, and T4 were taken as the period after avoidance measures. For symptoms scored by the physician, TO, T1, and T2 were taken as the period before avoidance measures, because all avoidance measures were applied at T2 and we expected a delay in clinical parameters afterwards. The confidence limit was set at 5% [15].

RESULTS

In Enkhuizen the mean monthly water-vapour pressure difference outdoors and indoors was 399 Pa at 3.8 • C outdoor temperature. In Zeist these parameters amounted to 440 Pa and 2.3"C respectively. Therefore, both dwellings are classified as laying on the boundary of (Dutch} indoor climate class II and Ill.

81

Clinical efficacy Patient 3 unexpectedly emigrated. Therefore, the end value of total- and specific serum lgE are missing. Patient 1 was sensitized against domestic mites and pets only. The other two patients (2 & 3), however, were sensitized against a greater variety of domestic allergens (mites, pets and moulds), rodents, yeasts (Pityrosporum and Candida), pollen and foods such as fish. The atopic dermatitis symptoms of these patients used to improve after a vacation period in France or on the Dutch Antilles. No statistical significant changes in skin test and specific lgE values were found after avoidance measures were taken (Table 1).

Total serum lgE of patient 1 increased up to 30% of the initial value. However, total serum lgE value of patient 2 decreased from 17,200 kU/1 before avoidance measures had been taken to 6,429 kU/1 at the end of the trial; a decrease of 63% (Table 1 ). After avoidance procedures were executed, blood eosinophils stayed at normal level (s 350 /mm3 [16]) for patient 1 and 3, but blood eosinophils of patient 2 lowered to the normal level (Table 1 ).

Initial and end values of symptom scores are given in Table 2. On the whole, no statistical difference was found between judgement of the eczema symptoms by physician and patient (p > 0.05).

Severity and extensiveness of atopic dermatitis for patient 1, judged by the physician showed no significant improvement (p > 0.05). Nevertheless, patient 1 herself scored a significant improvement of the severity of atopic dermatitis and of rhino-asthmatic symptoms after avoidance measures were executed (p < 0.03).

Atopic dermatitis symptoms decreased significantly in severity for patient 2 and 3 from the physician's standpoint (p < 0.05). However, the extensiveness of the atopic dermatitis did not change significantly after avoid­ance measures had been taken for either of the patients according to the physician.

Patient 2 scored a significant improvement in severity and extensiveness of his atopic dermatitis (p < 0.02). He scarcely scored rhino-asthmatic symp­toms. Patient 3 did not score significantly differently before and after perform­ance of avoidance measures concerning eczema symptoms (p > 0.05). However, he did score a significant increase in rhino-asthmatic symptoms after avoidance procedures were executed.

Table 2. Initial and end values of symptoms scores

Clinical symptoms

Eczema Rhinitis I asthmatic

Patient Scored by the patient Scored by the patient

severity extensiveness

initial end end initial end initial end value value value value value value value

77 109 5' 1.8 1.3 7 3'

2 345 6' 6.3 4.2' 0 0

3 207 20' 3 0. 0.2 0 3'

Patient 1 = ~ (29 y~); Patien~ 2 .= o (19 years); Patient 3 = o (15 years), brother of patient 2. nd = not done; * = difference Significant at 5% level.

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Table 3. lnitial and end values of guanine and dust exposure

Guaoine exposure (g I dust) Dust exposure (g)

! Patient initial value end value initial value end value

1 49 32 88 109

630 194* 186 191

3 659 193* 189

Patient 1 ~ (29 years); Patient 2 o (19 years); Patient 3 o (15 years), brother ofrtient 2. * = difference significant at 5% level with exclusion of the figures of tlie mite season (T3

Both the dermatologist and patient 1 did not report any change in medication use before and after allergological intervention. The patient kept using corticosteroids from class II and Ill. The medication for patient 3 did not change either concerning corticosteroid. He kept using corticosteroid of class I. However, at the end of the trial he had ceased to use wood-tar preparations. Patient 2 used less medication after the avoidance measures. He refrained from corticosteroids (class I) and wood-tar preparations, and used daily-care prepara­tions only.

Technical efficacy Changes in severity and extensiveness of atopic dermatitis and rhinitis-asth­matic complaints scored by the patients, were equal to changes in guanine exposure (p > 0.05). The opposite was found for the changes in dust exposure and changes in severity and extensiveness of the atopic dermatitis (p < 0.05). Changes in rhinitis-asthmatic symptoms were, however, equal to changes in dust exposure (p > 0.05). At the end of the trial, total guanine exposure decreased by 70% in Zeist and by 35% in Enkhuizen (Table 3). In both houses, total guanine exposure reached a maximum in the mite season at T3, 4 months after the start of the avoidance procedures. Therefore, guanine exposure in the living room, all bedrooms, and other rooms was compared before and after avoidance measures, with exclusion of the mite season values of guanine (T3l thus excluding the effect of seasonality of mite population growth. This resulted in a statistical decrease in guanine exposure at the end of the study in Zeist (p = 0.021 }, but not in Enkhuizen (p > 0.05). No significant decrease in dust exposure was found (p > 0.05) in either house (Table 3).

In Enkhuizen, duvets were washed almost every month and pillows once every other month. In Zeist, duvets and pillows were washed every 6 weeks. The washable duvets and pillows of the parents were washed once every 10 weeks (Enkhuizen) or 16 weeks (Zeist).

The newly purchased washable duvets and pillows had significantly more mites at the end of the study. An increase of 52% of the total mite numbers at the introduction of the washable bedding is seen. Acarex values of washable bedding remained, however, beneath the no sensitization level of Acarex 1 + [17].

Use of mattress covers held total mite numbers under the no sensitization risk of 100 mites per gram dust [17] on four of the seven covers. In the mite season (T3), total mite numbers exceeded this level on all covers. Acarex values remained beneath 1 + during the whole trial.

In comparing total mite numbers isolated from mattresses before the introduction of the mattress covers with mite numbers from mattress covers at the end of the study, no significant difference is seen after 11 months in use

83

(Enkhuizen) and 8 months in use (Zeist). Encasement of mattresses resulted however, in a significant reduction in mite numbers on the exposed mattress surface immediately after use; mattress surface before encasing versus cover surface.

Acaricidal treatment of home-textiles generally gave no statistical difference in guanine exposure before and after treatment (p > 0.05). But Acarex values of heavily mite-infested floor-textiles (Acarex ;;::: 2 + in Zeist} dropped in 3 of the 4 cases to Acarex 1 + .

In Enkhuizen 31 walls were vacuumed. In dust collected from 28 walls mites were found. In Zeist, mites were found in the collected dust on all the 34 vacuumed walls. Mites found on dwelling inner walls and room partitions were significantly higher in Zeist compared to those in Enkhuizen (p < 0.05). In both houses the numbers of mites found on the total wall surface decreased at the end of the trial (Table 4). Maximum amount of dust collected in Zeist at TO being 3.15 g on a wall (median = 0.08 g) and at T4 0.51 g on a wall (median = 0.03). In Enkhuizen the maximum amount of collected dust was found at T4, namely 0.32 g on a wall (median = 0.01 g). Here, the maximum initial amount was 0.06 g on a wall (median = 0.02 g) (Table 4).

On adhesive-tape samples, taken from dwelling inner walls and room partitions several mould and mite species, and other arthropods such as dust lice were found. The most abundant mite species found in adhesive-tape samples taken from fungal spots on inner walls were fungal eating mites such as Tarsonemoidae and G/ycyphagidae, whereas in wall-dust samples house dust mites (Pyroglyphidae) were the most abundant mite species.

Of the mould species grown from adhesive-tape Cladosporium herbarum was most abundant. Other mould species found were also air-borne mould species such as Penicillium and Aspergillus.

DISCUSSION

In both houses indoor climate rested at the boundary of the (Dutch) indoor climate classes II and Ill. At this point the no-sensitization threshold for house dust mites is exceeded [18]. Dwellings were conventionally sanitated, but patients still had complaints and mites were still present in sizable numbers. This phenomenon was also observed in dwellings of rhinitic patients (7].

The avoidance measures applied were not of clinical benefit for all patients. A decrease in the severity of atopic dermatitis is scored by the phys­ician in two cases: the brothers from Zeist. One of the brothers (patient 2) scored significantly less symptoms after the avoidance measures had been taken, his total serum lgE value decreased, and his blood eosinophils decreased to normal level. Also a drop in his medication use was seen. The severity and extensiveness score assessed by the other brother did not change significantly. He (patient 3), however, scored an increase in rhino-asthmatic complaints. This was probably caused by the exposure to tree pollen, since the trial ended in March. Patient 1 did score an improvement in the severity of her atopic dermatitis after avoidance measures had been taken, but she continued to use steroids of class II and Ill.

In some previous studies, avoidance measures were clinically successful, while others showed no clinical improvement at all [4]. This might be explained by differences in the technical competence of the applied avoidance measures. We, however, used the same measures in the two dwellings. Patient's compliance regarding the frequency of washing beddings and avoiding other

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Table 4. Total number of vacuumed walls in Enkhuizen and Zeist and the collected amount of dust with the and mites. Mite numbers are given per gram dust and per square meter

ENKHUIZEN Initial value End value

Vacuumed walls 31

Total wall surface vacuumed in nr 134

Maximum of collected dust amount in gram 0.06 0.32 (median) (0.02) (0.01)

Total number of mites/gram dust 73 9

Total number of mites/m2 wall surface 0.4 0.08

ZEIST Initial value End value

Vacuumed walls 34

Total wall surface vacuumed in m2 146

Maximum of collected dust amount in gram 3.15 0.51 (median) (0.08) (0.03)

Total number of mites/gram dust 101 54

Total number of mites/m2 wall surface 2 0.7

allergens such as food and pets, which were not involved in this avoidance programme, might explain the difference found in clinical efficacy. On the other hand, mite avoidance measures could be not feasible in some atopic dermatitis cases. A further possible explanation is that the reduction of inhalant allergen exposure obtained is not sufficient in some atopic dermatitis cases. Other possible causes of atopic dermatitis could be important, with additional dietary measures or medical treatment being necessary [19].

Another explanation for the discrepancy in clinical success of the measures might be that threshold values for mite exposure eliciting atopic dermatitis manifestation differ between individuals. In Zeist, patient 2 and 3 were exposed indoors to guanine and dust to the same extent, but only patient 2 showed an improvement in his atopic dermatitis after technically successful avoidance. The two brothers differ in sensitization to food and tree pollen. Differences in relevant outdoors allergen exposure could be the cause of the discrepancy found in the clinical success of the avoidance measures.

The fact that the severity and the extensiveness score of patient and physician do not differ statistically, demonstrates that patients are competent judges to their own eczema.

Guanine exposure decreased significantly after avoidance measures had been taken in Zeist only. In Enkhuizen, no such reduction was obtained. It should be noted that in this dwelling guanine exposure was low at the begin­ning of the study. Dust exposure contrary to guanine exposure did not change during the trial as was reported earlier [7).

In dwellings that were intensively cleaned, guanine exposure fluctuated, influenced by season with a peak in the mite season [7]. In the mite season, the avoidance measures did not lead to a reduction of mite numbers and guanine exposure, indicating that the frequency of applying avoidance measures should be enhanced in the mite season. Future studies will have to include more than one mite season.

All three short-term avoidance measures applied, i.e. washing of duvets and pillows, encasing of mattress, and treatment of carpets and upholstery with

85

Acarosan have shown their technical efficacy in the laboratory [20 - 23]. In this trial, mite numbers increased in the washable beddings, but

guanine, assessed by Acarex, did not accumulate during the course of time. Mites are removed by the mechanical effects of washing [18], as was also seen with dry cleaning of blankets [24]. In another home study, it has been observed that regular washing of mattresses, placed in heated rooms, over a period of two years led to a reduction in HOM populations [18].

Though inhabitants were positive about the fact that duvets and pillows could be washed, adults had practical problems like the use of two separate duvets on a double bed, which is not common in the Netherlands. It resulted in the infrequent use of the washable duvets.

In this home-study, encasing of mattresses for 3 months use or less resulted in a decrease of mite exposure. However, in the mite season, mite numbers increased, also on top of the covers. In other mite avoidance studies with mattress covers, all done from January till July, no increase in mite­population or mite allergen was found on the cover [25;26]. During this whole study, exposure to mite allergens from mattress covers, measured by guanine amount (Acarex), stayed below the proposed risk level for sensitization, but mite colonisation was not prevented. Colonisation is possible by migration of mites through zips and other fastenings [20]. Other home-studies have demonstrated that use of mattress-covers in bedrooms of asthma patients for a short period (4 to 12 weeks), next to cleaning procedures, resulted in a decrease of atopic dermatitis, asthma and rhinitis symptoms [27- 29].

When covers are used around old mattresses, they have to be washed. Inhabitants should protect themselves when mattress-encasings are stripped from the mattresses, since mite numbers in these mattresses stay above the proposed risk level for a prolonged period of time. Considering this, it would be advisable to use mattress-encasings only around new mattresses.

Contrary to earlier findings Acarosan treatment of home-textiles did not always result in a decrease of guanine exposure [7]. The Acarex value of heavily infected items decreased. This was reported previously in the study of Ridout et al [30]. There, acaricidal treatments of home-textiles had more effect in objects with an initial Der p I concentration of more than 1 0 pg/g than in those with a lower level of pollution. Furthermore, in this study Acarosan treatment was repeated after six months, while under laboratory conditions a repetition after two months was found to be more effective [31].

Mites and moulds were found on walls, but in lesser amounts than in textiles, as was also found earlier [32]. On walls, fungi-eating mites were the most abundant mite species found in adhesive-tape samples, contrary to the findings in total wall dust samples, in which house dust mites were the most abundant species. This is not surprising, since adhesive-tape samples were mostly taken from mould-ridden spots. Mould-ridden niches proved to contain more fungi-eating mites than non-mould ridden spots [10].

Mite avoidance measures that are technically effective under laboratory conditions, may have a different efficacy under domestic conditions caused by technical and seasonal limitations. In this study, clinical benefit is achieved only in the case of severe atopic dermatitis. Apparently, the feasibility of avoidance measures in dwellings is influenced by the severity of the disease. Besides this, individual threshold levels for mite exposure seem to differ. In moderate cases of atopic dermatitis, management of indoor humidity should follow the short­term allergen avoidance procedures. In future avoidance studies the clinical benefit of short-term avoidance measures should be preferably examined with severe atopic dermatitis patients only.

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ACKNOWLEDGEMENT

We are grateful to the inhabitants for allowing us into their homes. We thank the patients for their cooperation; P .A.C. van Wijk for intracutaneous testing; W.W.C. van der Horst-Cator, J. Scharringa and drs L.H.M. Walters for aiding in the analysis of the dust samples; student employment agency and their stu­dents (SUSA) for their assistance in sampling; E.M.P. Vos for aiding in patient instructions; drs S.A.R. Kort for aiding in the input of data in D-base IV; O.G. Kort BSc. for computer program assistance. Finally, we thank the Stichting Minibiologisch Onderzoek (SMO), Utrecht, the Netherlands for financial support.

REFERENCES

1. Volksgezondheid toekomst verkenning. De gezondheidstoestand van de Nederlandse bevolking in de periode 1950- 2010. RIVM. Den Haag: Sdu, 1993.

2. Bruijnzeei-Koomen C, Mudde GC, Bruijnzeel PLB. Die Pathogenese der atopischen Dermatitis. Allergologie 1990; 13: 325-338.

3. Dust mite allergens and asthma: Report of a second international workshop. J Allergy Clin lmmunol 1992; 89: 1046-1060.

4. Collof MJ, Aters J, Carswell F, Howarth PH, Merrett TG, Mitchell EB, Walshaw MJ, Warner JO, Warner JA, Woodcock AA. The control of allergens of dust mites and domestic pets: a position paper. Clin Exp Allergy 1992; 22:(suppl 2): 1-28.

5. Costa C, Rillet A, Nicolet M, Saurat JH. Scoring atopic dermatitis: The simpler the better? Acta Derm Venerol 1989; 69: 41-45.

6. Hanifin JM, Rajka G. Diagnostic features of atopic dermatitis. Acta Derm Venereol (Stockh) 1980; (suppl 92): 44-47.

7. Kniest FM, YoungE, Praag van MCG, Vos H, Kort HSM, Koers J, De Meat­Bleeker F, Bronswijk van JEMH. Clinical evaluation of a double-blind dust mite avoidance trial with mite-allergic rhinitic patients. Clin Exp Allergy 1991; 21: 39-47.

8. Hees RPJ, van. Vochtproblemen in bestaande woningen. Rapport 151 Stichting bouwresearch, Rotterdam, 1986: 185 pp.

9. Kniest FM, Wolfs BG, Vos H, Duchaine BOI, van Schayk-Bakker MJ, de Lange PJP, Vos EMP, van Bronswijk .... IEMH. Mechanisms and patient compliance of dust-mite avoidance regimens in dwellings of mite-allergic rhinitic patients. Clin Exp Allergy 1992; 22: 681-689.

10. Kort HSM. Mites, Dust lice, Fungi and their interrelations on damp walls and room partitions. In: Sommeijer MJ, van der Blom J. eds. Proc Exper Appl Entomol, N.E. V. Amsterdam 1990; 1: 63-68.

11. Voorhorst R, Spieksma FTh, Varekamp H. House dust atopy and the house dust mite. Stafleu, Leiden, 1969: 159 pp.

12. Bronswijk van JEMH. House dust biology for allergists, acarologists and mycologists. NIB, Zeist, 1981: 105-127, 258.

13. Bischoff E, Schirmacher W. Investigations of allergen-containing dust samples from the interior of the house. In: Boehm G, Leuschner RM eds. Advances in Aerobiology. Birkhauser, Basel: 1987; 51:189-196.

14. Farmaco-therapeutisch Kompas. Ziekenfondsraad, Amstelveen: 1993: 428-445.

15. Siegel S. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York: 1956.

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16. Wassom DL, Loegering DA, Solley GO, Moore SB, Schooley RT, Fauci AS, Gleich GJ. Elevated serum levels of the eosinophil granule major basic protein in patients with eosinophilia. J Clin Invest 1981; 67: 651-661.

17. Platts-Mills TAE, de Week AI. Dust mite allergens and asthma--A world wide problem. J Allergy Clin lmmunol 1989; 83: 416-427.

18. Schober G. Control of allergenic mites and fungi in house dust. Ph.D. thesis. State University of Utrecht, Utrecht, the Netherlands, 1991.

19. Platts-Mills TAE, Deuell B, Smith A, Kolmer H, Wilson B. Airborne allergens in atopic dermatitis. In: van Bronswijk JEMH, Baart de Ia Faille H, Bruijnzeei-Koomen CAFM, eds. Eczema and the environment. On the 75th anniversary of dermatology at Utrecht University Hospital, the Netherlands (1919- 1994). Department of Dermatology, Utrecht Univer­sity, Utrecht, 1994: 73-82.

20. Kniest FM, Liebenberg B, Ahr A. Mattress-encasings as a barrier for mites and airborne dust. J Aerosol Sci 1992; 23: S551-S554.

21. Andersen A., & Roesen J. House dust mite, Dermatophagoides ptero­nyssinus, and its allergens: effects of washing. Allergy 1989; 44: 396-400.

22. Schober G, Kniest FM, Kort HSM, De Saint Georges Gridelet DMOG, van Bronswijk JEMH. Comparative efficacy of house dust mite extermination products. Clin Exp Allergy 1992; 22: 618-626.

23. Mcdonald LG, Tovey E. The role of water temperature and laundry pro­cedures in reducing house dust mite populations and allergen content of bedding. J Allergy Clin lmmunol 1992; 90: 599-608.

24. Vandenhove T., Soler M., Brinbaum J., Charpin D., Vervloet D. Effect of dry-cleaning on mite-allergen levels in blankets. (Abstract). J Allergy Clin lmmunol 1992; 89: 257.

25. Bronswijk van JEMH. Colonisation and its prevention on house floors and in mattresses with Dermatophagoides pteronyssinus (Acari: Sarcoptiformes) in a center for asthmatic children. Ent Exp Appl, 1974; 17: 199-203.

26. Owen S, Morganstern M, Hepworth J, Woodcock A. Control of house dust mite antigen in bedding. Lancet 1990; 17: 396-397.

27. Roberts DLL. House dust mite avoidance and atopic dermatitis. Br J Dermatol 1984; 110: 735-739.

28. Murray AB, Ferguson AC. Dust-free bedrooms in the treatment of asthmatic children with house dust or house dust mite allergy: a controlled trial. Pediatrics 1983; 71: 418-422.

29. Howarth PH, Lunn A, Tomkin S. Bedding barrier intervention in house dust mite respiratory allergy. Clin Exp Allergy 1992; 22: 140 (Abstract).

30. Ridout S, Twiselton R, Matthews S, Stevens M, Matthews L, Arshad SH, Hide DW. Acarosan and the Acarex test in the control of house dust mite allergens in the home. Br J Clin Pract 1993; 47: 141-144.

31. Koren LGH. Long term efficacy of acaricide against house dust mites (Dermatophagoides pteronyssinus), in a semi-natural test system. In: Wildey KB, Robinson WH. eds. Proceedings of the 1st international conference on insect pests in the urban environment. Wheatons, Exeter: 1993: 367-371.

32. Kort HSM. Allergenic mites on mineral walls and in textiles. In: Wildey KB, Robinson WH. eds. Proceedings of the 1st international conference on insect pests in the urban environment. Wheatons, Exeter: 1993: 119-122.

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CHAPTER IV GENERAL DISCUSSION & SUMMARIES

IV.1 GENERAL DISCUSSION

89

90

GENERAL DISCUSSION

Aim of the study was to structure domestic allergen avoidance, while including indoor walls and room partitions, and to understand the ecological relationship on these walls and partitions. Ecological relationships were examined in laboratory and home studies (Chapter II). In addition, mould and mite avoidance procedures were executed in houses of allergic patients (Chapter 1111.

A new wall ecosystem

Organisms In homes, mites are present in combination with a variety of mould species in home textiles [7]. On walls, mites are found in the presence of xerophilic and meso-hygrophilic mould species (Chapter 11.2.1; 11.2.2), while dust lice are associated with meso-hygrophilic moulds only (Chapter 11.2. 11. In addition to moulds, mites, and dust lice, other arthropods such as plant lice and exuviae of silverfish were discovered on walls. These wall inhabitants may be used as bio­indicators of physical factors, such as humidity in houses (Chapter 11.2.1 ). In the future a list of these bio-indicators should be made and their reliability as an indicator should be studied in detail. Recently, cat (Fe/ d II and mite (Der f 11 allergens could be detected on wall surfaces too [48].

Interrelationships between wall inhabitants

Nutrients It has been known for some time that fungi play a role in the development of mites [7;42]. Xerophilic fungi are of nutritional value to pyroglyphid mites, whereas storage mites live merely on a fungal diet [6; 16;29]. Mould scores correlate with relative humidity for the dust-eating mite Dermatophagoides pteronyssinus, but not for the fungal-eating storage mite Glycyphagus domes­ticus (Chapter 11.1.2). Storage mites inoculated on mouldy surfaces pastured on these surfaces (Chapter 11.1.21.

A nutritional relationship is observed on walls between moulds present and storage or fungi eating mites such as Tarsonemids. Laboratory studies showed that Pyroglyphids are less dependent on the presence of moulds when compared to storage mites [40]. In the presence of moulds, storage mite can survive in granaries even in the absence of grain. Fungi may function as the sole substrate as well as an enhancement of the nutritional value of the substrate [331 (Chapter 11.1.11.

Fungi can be ascribed more than a passive role as a food source; they also have an active role in attraction of mites [45]. Probably this enhances the dispersal of their spores. Fungi use mites as a vehicle to distribute the spores; in the gut lumen of the house dust mite D. pteronyssinus spores of A. penicil­/oides are found [16]. A. repens germinated from faecal pellets of storage mites [21 ].

If man did not interfere, mould growth would be limited by grazing mites and dust lice. In their turn their populations would not be able to increase without limit, because predators like Cheyletus would hunt them.

Niche Different mite taxa and dust lice are present on walls with and without visible mould growth. Mites were seen on approximately 92% of the fungal ridden

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walls and on 74% of the walls without visible mould growth (Chapter 11.2.1). Total mite numbers were significantly higher on mould-ridden walls as com­pared to walls not soiled by fungi (Chapter II 2.2). This phenomenon is also observed in granaries, where mites thrive better in the surroundings of moulds [42].

A significant correlation is present between total mite numbers in textiles and on walls, probably contributable to the numbers in the category house dust mites. For non-pyroglyphid mites no such relation was found (Chapter 11.2.3). This could indicate that house dust mites on walls are aerogenically transported from dust reservoirs in textiles to the walls.

For house dust mites the conditions for population growth on walls are less suitable than in textiles. They can not cling to smooth surfaces, however. Walls serve as a niche for pyroglyphid mites, because the dust particles trans­ported by air contain human skin scales, which they digest. Furthermore, pre­digestion can take place through moulds living on wall surfaces. Humidity conditions are satisfactory, since the mites are able to absorb water from the air [2].

The growth of storage mite populations on wall surfaces starts as a focal problem, since they have a close nutritional relationship with moulds. Storage mites, however, can only inhabit walls if moulds are already present.

Previously, mouldy walls were reported as an excellent niche for storage mites such as Glycyphagus domesticus [26]. In this thesis the ecosystem concept was developed. Walls are not only an excellent niche for storage mites but appeared to be part of an independent ecosystem in dwellings.

Temperature and humidity The appearance of food sources in the shape of moulds on wall surfaces depends on temperature, soiling and humidity. Particularly the amount of time that the relative humidity reaches the level needed for germination of spores is of importance [1 0]. In bathrooms wall surface humidity may exceed 90% RH, but only for a short duration. In living rooms, however, the amount of time this peak value is reached, may be twice as long as, due to water-vapour input from adjacent kitchens [ 19]. Differences in hygroscopicity of surfaces also play a part in the successful germination of fungi [19;13].

Other physico-chemical factors

Soiling In addition to temperature and humidity, the availability of nutrients is of prime importance for mould growth [34]. In chapter 11.1.1 it has been demonstrated that soiling of indoor materials with artificial dust increases growth of the inoculated fungi. Soiling increased mould growth depending on the relative air humidity (Chapter 11.1.1 & Chapter 11.1.2). For a high air humidity it is found that: the higher the hygroscopicity and soiling of the surface, the quicker mould growth takes place. At a low relative humidity, the nature and amount of soiling plays an important role in ecosystem success (Chapter II. 1 .1). If they are soiled enough, moulds occur on the lenses of optical instruments [37]. But at high relative humidities ( < 90%} moulds may occur on glass that appears clean to the naked eye [44].

On soiled surfaces physical and chemical composition of the dirt influ­ences fungal growth, probably due to differences in hygroscopicity. Fungal development is more extensive on painted paper as compared to unpainted paper [19]. In chapter 11.1.1 this phenomenon has been demonstrated for

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finishing and furnishing materials. After 40 weeks, little fungal growth was seen on clean gypsum board and spruce wood, whereas no fungal growth was observed on clean carpet and mattress (Chapter 11.1.1 ).

Soiling causes a reduction in minimum Aw levels that are conducive to growth. The effect is more pronounced at a low temperature (12.C) than at a higher temperature (25 ° Cl [19]. In general, for clean surfaces, an increase of temperature results in a reduction of minimum Aw requirements for mould growth [19].

Ph Previously, effects of surface pH on mould growth were reported [31 ;34]. However, when surfaces are soiled, this effect is eliminated (Chapter 11.1.1; Chapter 11.1.2).

In conclusion: soiling of indoor surfaces enhances mould growth and it elimin­ates the influence of surface pH and hygroscopicity of the finishing or furnish­ing material.

Allergological survey

When inhabitants have allergological complaints while staying at home, an allergological survey should be carried out concerning the agents causing the complaints [41 ]. This survey should be held after relevant sensitization is assessed. The agents may be surveyed by air sampling and surface sampling, or by source investigation. In this thesis, air sampling was done by means of the 'open Petri-dish' method (Chapter 111.3) and was used to assess mould exposure. Surface sampling was done using a tape-imprint technique, and source sampling was done by vacuuming, both in order to make an inventory and to study the ecological relationships between moulds and mites. When health damage is due to mites, this last method is frequently used to assess exposure to allergenic house dust [35].

Damage to buildings due to mould growth is often evaluated by means of air or surface sampling. In addition indoor climate classes are assessed [25].

Air sampling The advantages and the disadvantages of air sampling were previously evalu­ated [5]. It was shown that not only the sampling method matters for the assessment of moulds, but also the media chosen [38;46]. In homes, surface samples provide more information regarding moulds present on the surface as compared to air samples [38].

Surface sampling Tape-imprinting of walls had the benefit that the damage-inducing moulds could be easily identified. In addition, it is a suitable technique to directly examine the interrelations of moulds and mites on humid walls (Chapter 11.2.2). Although, the fungi identified gave information about the prevailing humidity, no clarifica­tion could be obtained about the origin of the damage. This especially applies to meso-hydrofilic or hydrofilic mould species, since these can appear as second­ary and tertiary colonizers [19].

The disadvantage of tape-imprints is that only a relatively small part of the surface is sampled. Identification of mites to species level is often imposs­ible. Therefore, it has been suggested in chapter 11.2.1 that vacuuming of walls

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in addition to sampling with tape-imprints may help. Vacuuming of walls has the advantage that mites and other arthropods

can be isolated from the dust taken from the whole surface of the dust source (home textiles or walls). Species and stages can then be established. Species found give information about the ecological relationships. The disadvantage of wall dust samples is that the isolation of moulds by use of a dilution plate method is time consuming compared to isolation from tape-imprints.

Sampling expression Besides the sampling method, the expression of the density of the organisms found is of importance too [11 ]. Mite counts are usually expressed per unit weight, although there are differences in dust density. For reasons of compari­son to other studies, we expressed the numbers of mites found per unit weight. To compare mite numbers found in home textiles dust and in wall dust, mite numbers were also expressed per unit area (Chapter 11.2.3). This was done because of the differences in the dust density of the surface. So, in an allergological survey, air sampling gives information on exposure only, while with surface or source sampling information is obtained about ecological relationships in addition to exposure. Organisms should be expressed by weight and also per unit area when different habitats are compared.

Allergological exposure After the allergological inventory, allergological exposure is assessed and compared to the existing hygienic risk level for the allergens relevant to the patient (Chapter 111.2 & Chapter 111.3). Relevant allergen sensitization and relevant allergen exposure is assessed by the physician and biologists respect­ively (Chapter 111.2 & Chapter 111.3). Organisms found are tested for their proposed hygienic risk level regarding sensitization before avoidance strategies are designed (Chapter 111.2 & 111.3). For mites this risk level is set on 10 mites per g floor dust, 100 mites per g mattress dust, 0.6 mg guanine per g dust, or Acarex value 1 [35]. For moulds, however, no such risk level is yet acknowl­edged. Prahl suggest 1 mould colony found in winter by means of the 'open Petri-dish' method (20 minutes) or 16 in summer, as a guideline to mould­reducing measures [36]. These numbers were obtained in Denmark. Data from other areas are lacking.

For houses, a humidity risk level for mite development was set at the boundary between the (Dutch) indoor climate classes II and Ill [41].

Excretion products The allergenicity of house dust can be assessed with mite counts, mite aller­gens or with guanine amounts as variables [ 17].

Guanine Guanine is the main nitrogenous waste product of spiders and is also part of mite faecal pellets [7]. Guanine concentration in house dust is positively correlated with the amount of D. pteronyssinus (Der p I) allergens and with total mite numbers [8;30]. Guanine is used to assess mite-allergen exposure in dwellings [17;41]. It can be measured quantitatively by capillary zone electro­phoresis (Chapter 11.1.2) or semi-quantitatively by means of the Acarex test {Chapter 111.2, 111.3) to assess mite-allergen exposure.

In chapter 11.1.2 a correlation between total mite numbers and guanine concentration is seen for D. pteronyssinus. However, no such relation is detected for G. domesticus.

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The fungivorous character of storage mites probably causes a difference in excretion products between the storage mite G. domesticus and the dust-eating mite D. pteronyssinus. A change in faecal pellet composition from nitrogenous (guanine) to more carbohydrate rich, due to the fungal diet of the storage mites, could be the cause. Therefore, Berrens' hypothesis about the house dust allergen consisting of a peptide portion and a carbohydrate portion should be re­evaluated [3]. He postulated that the carbohydrate portion could degrade by means of Maillard reactions without losing allergenic activity [4]. This glycoprotein rich allergen was a chemically stable allergen, such as is seen for Der p I in common house dust (Chapter 11.1.3)

Another consequence of the fact that total mite numbers of G. domes­ticus did not relate with the guanine amount, might be that the Acarex test should not be used for the quantification of storage mite products as the mites live in a mouldy environment. Use of the Acarex test would then result in an under-estimation of mite-allergen exposure.

Differences in the diet of mites may have consequences for composition of their faeces and thus cause differences in the allergens excreted. This could be an explanation for the differences observed in cross-allergenicity between storage mites and house dust mites. In some RAST-inhibition studies, cross­allergenicity is found between storage mites and house dust mites [20;28], while others demonstrated a lack of cross-allergenicity [221 or no significant RAST correlation [1 ;23]. Another explanation might be the difference in exposure in patients tested [24].

In chapter 11.1.2 guanine concentration per mite is negatively correlated with total mite numbers for both D. pteronyssinus and G. domesticus. This can be caused by the fact that guanine was assessed in the dust only (exoskeletons and faecal pellets) and not from the mite body. Mites are able to store guanine in their body (18]. For D. farinae, grown in pure culture, guanine accounts for about 0.3% of the body mass [47].

Mite allergen In chapter 11.1.3 the stability of the mite allergen Der p I, in common house dust, was examined after mite extermination. This study was performed because most mite avoidance programmes merely include the extermination of mites [12]. After almost four years of incubation, at 75% relative humidity and 5 or 25 ° C, no significant reduction of Der p I is seen. This result demonstrates that even after mite extermination, home textiles remain allergen reservoirs. Therefore, mite-reducing procedures should include removal of allergens in addition to extermination of mites.

Allergological avoidance strategies

Conventional allergen avoidance strategies For atopic persons exposure to indoor allergens is related to allergic diseases [35]. In chapter 111.1 it is mentioned that the relationship between dust exposure and allergic inflictions has been known for hundreds of years. The most abundant mites of that time, however, were storage mites. These mites were also observed on walls together with moulds.

Avoidance strategies were restricted to the removal of the infested objects, the intensive cleaning, or improvement of ventilation.

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Modern allergen avoidance strategies Nowadays, it is recommended that the relevant allergen producers be identified before executing avoidance procedures [41].

As suggested by Kniest, all relevant allergen sources should be included in avoidance programmes [27]. This implies that inner walls and room partitions should also be part of mite and mould-reduction programmes. Although walls are not a main dust reservoir, they form enormous allergen accumulating surfaces in dwellings. Until now avoidance strategies were aimed at home textiles and included cleaning of dust reservoirs, and the removal and eradica­tion of allergen producers. Schober suggests combining these short-term measures with long-term measures, which involve humidity management [41].

Relevancy of wall inhabitants in allergic diseases Relevancy of house dust mites (Pyroglyphidae) and moulds in allergic disease is well documented. It is a less known fact that silverfish and dust lice also may elicit allergic reactions [39].

The presence of storage mites on the inner walls of houses might by an explanation for the fact that sensitization to storage mites is now also seen in urban populations. In the sixties, sensitization to storage mites was seen in rural populations, tropical regions or was related to someone's occupations [43]. Nowadays, 43% of patients allergic to house dust mites have specific lgE bodies for storage mites [14;15]. Furthermore, more than 50% of house dust allergists have positive skin-test reactions to storage mites [14;27]. These were all patients living in urban environments.

No differences in sensitization level are found between urban and rural populations [14;15]. Another indication for the clinical relevance of mites and moulds on wall surfaces might be that this niche sharing results in exposure to both organisms. Sensitization to both storage mites and fungi is seen in people living in urban areas (Chapter 111.2; Chapter 111.3) [32].

In the case study described in chapter 111.2, the patient was sensitized to both storage mites and moulds. It was evident that exposure to mites and moulds on wall surfaces led to an exacerbation of atopic dermatitis, since few home textiles were present.

Only limited success is achieved in reducing atopic dermatitis through the avoidance of mites [12]. However, all of these previous avoidance programmes only take home textiles into account, or hospitalization of patients. In this case, however, other avoidance schemes had to be developed, because walls were a major allergen source. A short-term programme for a rapid decrease of expo­sure was devised in addition to a long-term programme for a prolonged decrease of exposure. This was, as proposed by Schober, the ideal concept of mite management [41].

A structured approach towards allergen avoidance A structured approach of allergen avoidance starts with an assessment of relevant allergen sensitization and hyperreactivity and relevant allergen expo­sure. Followed by the design of an individual avoidance programme [9]. In this avoidance programme short-term measures should be combined with long term measures (Chapter Ill). Furthermore, the effect of the avoidance strategy should be evaluated by the physician. Preventive measures should be recommended after the evaluation of relevant sensitization and allergen exposure.

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Short-term measures Short-term measures included cleaning of dust reservoirs and surfaces, removal of allergens and killing of allergen producers (Chapter Ill). In chapter 111.2 a quick reduction of mite and mould exposure from home textiles was chosen by washing clothes, using washable mattresses and applying chemicals that combine intensive cleaning with extermination of organ­isms. The acaricide Acarosan® (benzyl benzoate) was applied for the few home textiles left. This acaricide had proven its efficacy in laboratory as well as in home studies [27;41]. Inner walls and room partitions were treated with Apesin Ap-100 (Mg-monoperoxy-phthalate-hexahydrate), which had not been used in houses before.

In the open study with atopic dermatitis patients, short-term measure­ments were executed only (Chapter 111.3). Acaricidal cleaning was combined with the use of mattress covers and regular washing of duvets. Washing of the duvets kept guanine concentrations beneath the proposed sensitization risk level [35]. The frequency of washing (once every six weeks) was, however, experienced as tiring by the inhabitants.

Use of mattress encasings resulted in a decrease of dust and mite ex­posure. However, the colonisation of mites on mattress encasings was not halted. Therefore, it is necessary to regularly clean mattress covers.

Short-term avoidance procedures involving acaricidal cleaning and barrier methods alone resulted in a decrease of severe atopic dermatitis (Chapter 111.3). However, in rhinitic patients a decrease in clinical symptoms was observed when acaricidal cleaning only was applied [27]. Apparently, a lower exposure is needed to reduce dermatitis symptoms than to reduce nose complaints.

Short-term mite-reducing procedures have proven their efficacy [12;27], but are not sufficient when patients are also exposed to mites and moulds on walls surfaces. In this event, long-term avoidance procedures should be executed in addition to short-term management of mites and moulds of inner walls.

Long-term measures Long-term measures were devised after a technical evaluation of the house by a building engineer and an assessment of the (Dutch) indoor climate class. Long­term management involved improvement of ventilation and dehydration of the humid walls. It was the first time that wall surfaces were included in an avoidance programme.

This multi-disciplinary home-sanitation programme proved to be effective. The (Dutch) indoor climate class went from IV (humid) to II (normally dry) [25]. Furthermore, patient total serum lgE and symptom scores decreased with 79% and 87% respectively. Above all, the patient was able to resume her work (Chapter 111.2).

Long-term measurements could be applied in houses of patients with a lower threshold level for mite exposure if a further reduction in allergen expo­sure could not be reached by short-term measures only, due to technical and seasonal limitations (Chapter 111.3). The execution of long- term avoidance strategies should be preceded by a technical evaluation of the building in addition to assessment of the indoor climate class. Indoor climate classes should be compared to the humidity risk level of mite development as described by Schober [41].

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Preventive measures Allergological preventive measurements in Dutch houses with a rapid effect should include mattress encasings around new mattresses only. In the long run, design or renovation of houses has to aim at (Dutch) indoor climate class II. With the correct level and type of ventilation, indoor climate can be kept at this level by the inhabitants for a number of years.

Evaluation Evaluation of the allergen avoidance programme should be done after 3 months of short-term allergen avoidance measures, and after 1 year of long-term allergen avoidance measures. Allergic symptoms should be evaluated by the physician and relevant allergen exposure should be evaluated by a biomedical and technically trained person. Allergic symptoms and allergen exposure should be compared to the hygienic risk level(s). When allergic symptoms do not decrease a revision of the avoidance programme should be made. In especially the case of atopic dermatitis also non-allergic factors should be considered.

Long-term sanitation methods should be performed in a larger number of houses in order to achieve generally applicable results. Furthermore, indoor walls and room partitions should be part of avoidance procedures in humid houses, because of the presence of moulds and mites. In addition to this, it will also be necessary to investigate the feasibility of avoidance programmes conducted by the inhabitants themselves. Avoidance programmes should be easy to conduct. These programmes should be taught in Building Engineering, since physical aspects of houses influence the allergen exposure from surfaces prone to moulds and mites.

A structured approach to allergen avoidance is a multidisciplinary approach consisting of short-term as well as long-term indoor environmental sanitation methods. They spread over the scientific and technical disciplines of bio­medical sciences and building physics.

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2. Arlian LG, Veselica MM. Water Balance in insects and mites (review). Comp Biochem Physiol. 1979; 64A: 191-200.

3. 8errens L. Structural studies of house dust allergens. Clin Exp lmmunol. 1970; 6: 71-74.

4. 8errens L. The chemistry of atopic allergens. In monographs in allergy. 1971; 7: Vlll-298.

5. Beaumont F. Aerobiological and clinical studies in mould allergy. Ph.D. thesis. Groningen, the Netherlands. 1985.

6. Bronswijk JEMH van, Sinha RN. Role of fungi in the survival of Dermato­phagoides (Acarina:Pyroglyphidael in house-dust environment. Environm Entomol. 1973; 2: 142-145.

7. Bronswijk JEMH van. House dust biology for allergists, acarologists and mycologists. NIB publishers Zeist, the Netherlands. 1981: 316 pp.

8. Bronswijk JEMH van. Guanine as a hygienic index for allergologically relevant mite infestations in mattress dust. Exper Appl Acarol. 1986; 2: 231-238.

9. Bronswijk JEMH van, Kort HSM, Koren LGH, Nes AMT van, Snijders MCL. Allergen avoidance in the dwelling environment. In: Eczema and the environment: On the 75th anniversary of dermatology at Utrecht Univer­sity, the Netherlands. (1919-1994). eds. Bronswijk JEMH van, Baart de Ia Faille H, Bruijnzeei-Koomen CAFM. 1994: 83-98.

10. Chowdhury S. Germination of fungal spores in relation to atmospheric humidity. lnd J Agric Sci. 1937; 7: 653-657.

11. Colloff MJ. Practical and theoretical aspects of the ecology of house dust mites {Acari: Pyroglyphidae) in relation to the study of mite-mediated allergy. Rev Med Vet Entomol. 1991; 79: 611-630.

12. Colloff MJ, Ayres J, Carswell F, Howarth PH, Merrett TG, Mitchell EB, Walshaw MJ, Warner JO, Warner JA, Woodcock AA. The control of allergens of dust mites and domestic pets: a position paper. Clin Exp Allergy. 1992; 22 {suppl 2): 1-28.

13. Coppock JBM, Cookson ED. The effect of humidity on mould growth on constructional materials. J Sci Food Agric. 1951: 534-535.

14. Dal Monte A, Tomasini C, Calipa V, Pederzoli P. The role of the sensitiza­tion to storage mites in the diagnosis of allergic respiratory diseases. Aerobiologia. 1992; 8: 419-422.

15. Debelit M, Lanner A. Haufigkeit von spezifischen lgE-Antikorpern gegen Hausstaub- und Vorratsmilben bei jungen Atopikern. Allergologie. 1993; 8: 323-328.

16. Douglas AE, Hart AE. The significance of the fungus Aspergillus peni­cilloides to the house dust mite Dermatophagoides pteronyssinus. Sym­biosis. 1989; 7: 105-116.

17. Dust mite allergens and asthma: Report of a second international workshop. J Allergy Clin lmmunol. 1992; 89: 1 046-1060.

18. Evans GO. Principles of acarology. C.A.B. international, Wallingford. 1992: 563 pp.

19. Grant C, Hunter CA, Flannigan B, Bravery AF. The moisture requirements of moulds isolated from domestic dwellings. lnt Biodeter. 1989; 25: 259-284.

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20. Griffin P, Ford AW, Alterman L, Thompson J, Parkinson C, Blainey AD, Davies RJ, Topping MD,. Allergenic and antigenic relationship between three species of storage mite and the house dust mite, Dermatophagoides pteronyssinus. J Allergy Clin lmmunol. 1989; 84: 108-117.

21. Griffiths DA, Hodson Ac, Christensen CM. Grain storage fungi associated with mites. J Econ Entomol. 1959; 52: 514-518.

22. Hage-Hamsten M van, Johanson SGO, Johansson E, Wiren A. Lack of allergenic cross-reactivity between storage mites and Dermatophagoides pteronyssinus. Clin Allergy. 1987; 17: 23-31.

23. Hage-Hamsten van M, Johansson SGO. Clinical significance and allergenic cross-reactivity of Euroglyphus maynei and other non-pyroglyphid and pyroglyphid mites. J Allergy Clin lmmunol. 1989; 83: 581-589.

24. Hage-Hamsten van M, Machado L, Barros MT, Johansson SGO. Compari­son of clinical significance and allergenic cross-reactivity of storage mites 8/omia kulagini and Lepidoglyphus destructor in Sweden and Brazil. Allergy. 1990; 45: 409-417.

25. Hees RPJ van. Vochtproblemen in bestaande woningen. Rapport 151, Stichting bouwresearch, Rotterdam. 1986: 185 pp.

26. Hora AM. On the biology of the mite, Glycyphagus domesticus de Geer, (Tyroglyphidae, Acarina). The Annals of Applied Biology. 1939: 483-494.

27. Kniest FM. The management of dust allergens. Ph.D. thesis. Nijmegen, the Netherlands. 1990: 1 27 pp.

28. Luczynska C, Griffin P, Davies RJ. Topping MD. Prevalence of specific lgE to storage mites (A. siro, L. destructor and T. longior) in an urban popula­tion and crossreactivity with the house dust mite (D. pteronyssinus). Clin Exp Allergy. 1990; 20: 403-406.

29. Lustgraaf B van de. Ecological relationships between xerophilic fungi and house dust mites (Acarida: Pyroglyphidae). Oecologia. 1978; 33: 351-359.

30. Le Mao J, Pauli G, Tekaia F, Hoyet C, Bischoff E, David B. Guanine content and Dermatophagoides pteronyssinus allergens in house dust samples. J Allergy Clin lmmunol. 1989; 83: 926-933.

31. Magan N, Lacey J. Effect of temperature and pH on water relations of field and storage fungi. Trans Br Mycol Soc. 1984; 82(1): 71-81.

32. MOsken H, Bergmann KCh. Storage mites: frequency of sensitization and clinical allergy. Allergy Clin lmmunol News Suppll. 1991: 146.

33. Parkinson CL, Jamieson N, Eborall J, Armitage DM. Comparison of the fecundity of three species of grain store mites on fungal diets. Exp Appl Acarol. 1991; 12: 297-302.

34. Panasenko VT. Ecology of microfungi. Bot Rev.1967; 33: 189-215. 35. Platts-Mills TAE, de Week AL. Dust mite allergens and asthma- a

worldwide problem. J Allergy Clin lmmunol. 1989 83; 416-427. 36. Prahl P. Reduction of indoor airborne mould spores. Allergy. 1992; 47:

362-365. 37. Raper KB, Fennell Dl. The genus Aspergillus. Robert E. Krieger Publishing

Company Huntington. New York. 1977: 190 pp. 38. Reenen-Hoekstra vanES, Samson RA, Verhoeff AP, Wijnen van JH.

Brunekreef B. Detection and identification of moulds in dutch houses and non-industrial working environments. Grana. 1991; 30: 418-423.

39. Rijckaert G, Thiel Cl, Fuchs E. Allergenitat von Silberfischen und Staublausen. In: Fast releasing allergens from some organisms living in house dust. Ph.D. thesis, Nijmegen, the Netherlands. 1981: 33-39.

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40. Rodriguez JG, Rodriguez LD. Nutrional ecology of stored-product and house dust mites. In: Nutritional ecology of insects, mites, spiders, and related invertebrates. eds: Slansky F, Rodriguez JG. New York, John Wiley. 1986: 345-368.

41. Schober G. Control of allergenic mites and fungi in house dust. Ph.D. thesis. Utrecht, the Netherlands. 1991: 179 pp.

42. Sinha RN. Acarine community in the stored rapeseed ecosystem. In: Acarology VI. eds: Griffiths DA, Bowman CE. Ellis Horwood limited, Chichester. 1984; 2: 1017-1025.

43. Spieksma FThM. Domestic mites: their role in respiratory allergy. Clin Exp Allergy. 1991 ; 21 : 655-660.

44. Tomkins RG. Studies of the growth of moulds. Roy Soc Proc B. 1929; 105: 5-401.

45. Thomas CM, Dicke RJ. Attraction of the grain mite Acarus siro (Acarina: Acaridae), to solvent extracts of fungi associated with stored food commodities. Ann Entomol Soc Am. 1972; 65: 1069-1073.

46. Verhoeff AP, Wijnen van JH, Boleij JSM, Brunekreef 8, Reenen-Hoekstra van ES, Samson RA. Enumeration and identification of airborne viable mould propagules in houses. Allergy. 1990; 45: 275-284.

47. Yokoyama H, Matsuki H, Misawa K, Takaoka M, Kasuga H. Guanine levels in house dust as a means of estimating the mite population. Tokai J Exp Clin Med. 1990; 15: 477-483.

48. Wood RA, Mudd KE, Eggleston PA. The distribution of cat and dust mite allergens on wall surfaces. J Allergy Clin lmmunol. 1992; 89: 126-130.

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In our homes we are protected from noxious outdoor environmental factors. Protection from indoor environmental factors, however, is limited. Several biological agents attack our house materials and health. This thesis is focused on the harmful effects of moulds and mites on indoor surfaces, home textiles and health.

Soiling is one of the conditions conductive to mould growth on indoor surfaces. Little fungal growth is seen after 40 weeks of incubation on clean gypsum board and clean spruce wood. No fungal growth is seen, however, on clean carpets and mattress. Soiling enhances the growth of moulds and it eliminates the influence of surface pH and hygroscopicity of the clean surface (Chapter 11.1.1).

Indoor surfaces in humid surroundings are not only inhabited by moulds but also by mites (Chapter 11.2.1, 11.2.2, 111.2, 111.3). These organisms live together with other arthropods on walls in a so-called wall ecosystem. They can be used as bio-indicators of physical factors, such as humidity in houses (Chapter 11.2.1).

Pyroglyphids, storage and fungi eating mites (Tarsonemids) are found on walls with visible mould growth (Chapter 11.2.2). Moulds occurring on humid walls belong to xerophilic and mesohydrophilic species, such as Aspergillus penicilloides and Cladosporium herbarum respectively. Moulds and mites on walls have a nutritional relationship. This does not mean, however, that visible mould spots should be present. Fine fungal mycelia, invisible to the naked eye, provide an adequate meal for wall-inhabiting mites (Chapter 11.2.1 ). Moulds in their turn use mites and dust lice as a vehicle for their spores.

House dust mites (Pyroglyphidae) can also be obtained from walls without visible mould growth. These mites and their food source, skin scales, will be transported from textile dust-reservoirs to the walls by air. House dust mites in textile dust and wall dust are indeed positively correlated (Chapter 11.2.3). For non-pyroglyphids no such correlation is found.

The storage mite Glycyphagus domesticus has a different guanine excretion from the dust eating mite Dermatophagoides pteronyssinus. This is probably caused by the nutritional interaction between moulds and storage mites. Total numbers of G. domesticus are not related to guanine concentration present, whereas for D. pteronyssinus a relation is found between total mite numbers and guanine concentration in the dust (Chapter 11.1.2). In mouldy surroundings, this difference in guanine excreted may have consequences for the assessment of mite and allergen exposure using guanine.

Mite exposure can also be assessed by mite counts or by allergen amounts. The house dust mite allergen Der p I is stable in house dust, for almost 4 years under simulated house conditions (Chapter 11.1.3). This has the consequence that in mite avoidance studies older dust should be removed too. Mite avoidance studies should combine extermination of mites with the removal of allergens.

Mite avoidance used to include the removal of infested home textiles only. Before World War II home textiles were predominately infested by storage mites. In those days house dust mites only occurred on dried hides and in bird nests. After World War II, due to changes in home-textile materials, house dust mites became the most abundant domestic allergen producers (Chapter 111.1 ). The clinical relevance of storage mites diminished. Recently, people sensitive to storage mites have been found in urban environments, in addition to rural regions and places of work in the food industry. In the current urban environ-

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ment allergic patients are exposed to relevant numbers of house dust mites, storage mites and moulds in their own dwellings (Chapter 111.1 ).

Before avoidance programmes are executed an allergological inventory is done. Vacuuming, a tape-imprinting technique and the open 'Petri-dish' method are used to get an indication of the exposure level (Chapter 111.2 & 111.3). Home textiles as well as inner walls and room partitions are sampled. Due to the fact they were situated in humid houses, inner walls showed to be a relevant allergen accumulating surface for mite and mould excretions and secretions (Chapter 111.2).

In such a humid house (Dutch indoor climate class IV), inhabited by an atopic dermatitis patient, a multidisciplinary home sanitation programme was supervised by a physician, biologist and building engineer, but executed by the inhabitants themselves. Although, this dwelling was decorated with few home textiles, the patient had severe complaints. Therefore, an unusual home sanitation programme was devised. This sanitation programme combined a short-term phase for a rapid decrease of allergen exposure with a long-term phase for a prolonged decrease of allergen exposure. The short-term phase included regularly washing, removal and cleaning of infested materials and extermination of allergic organisms. The long-term phase included prevention of allergen exposure by use of a washable mattress and combined effective ventilation with humidity management. This involves drying of inner walls and room partitions. This multidisciplinary programme led to a gradual drop of total lgE and clinical symptom scores in the patient studied. Beside this, the patient resumed work (Chapter 111.2).

In the houses of three other atopic dermatitis patients, with a Dutch indoor climate class on the boundary of class II and Ill, a home sanitation programme was carried out without humidity management (Chapter 111.3). This short-term sanitation programme involved the cleaning of infested surfaces, exterminations of mites by use of an acaricide and prevention of allergen exposure by use of mattress covers and washable duvets and pillows.

This short-term home sanitation programme did not result in a clinical improvement of all three patients. However, avoidance measures resulted in a decrease of guanine exposure. Changes in guanine exposure were equivalent to changes in symptoms scored by the patient and contrary to changes in dust exposure.

Acaricidal treatment of home textiles with Acarosan• only resulted in a decrease of Acarex to 1 + (0.6 mg guanine per gram dust), in the case of heavily infested floor-textiles (Acarex ~ 2+ = < 10 mg guanine/ g dust). Use of mattress covers and washable beddings attained a Acarex value beneath the no-sensitization risk of 1 +. However, mite numbers increased in the autumn. The opportunity to wash duvets and pillows was experienced as an advantage, but washing these beddings regularly was considered as too time-consuming and was therefore not done frequently enough (once every six weeks) with all supplied washables. Avoidance measures were technically successful in reducing mite exposure, but clinical benefit was only obtained in the patient with severe atopic dermatitis.

In humid environments, inner walls and room partitions form a large allergen accumulating surface inhabited by moulds, fungi eating mites (Tarsonemoidea, Glycyphagidae and Acaridae) and also house dust mites (Pyroglyphidae). Home sanitation programmes should not only monitor mite or allergen exposure and their clinical effects, but also the feasibility of avoidance measures. In addition, avoidance programmes should be not too time-consum­ing and easy to perform by the inhabitants, in order to enhance compliance.

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This should be taken into account in the design or renovation of houses. A structured approach to allergen avoidance comprises short-term

measures for a rapid decrease in allergen exposure, combined with long-term measures for prolonged decrease of allergen exposure. Furthermore, in addition to home textiles, indoor walls and room partitions should be part of avoidance programmes.

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Woningen zijn gebouwd ter wering van schadeljjke invloeden van buiten. De bescherming tegen schadelijke binnenmilieu-effecten is veelal beperkt. Dit proefschrift behandelt een aantal allergologische effecten van normale biologische agentia in het huiselijke binnenmilieu: schimmels en mijten, die hun leefmilieu gevonden hebben op minerale oppervlakken binnenshuis en in het woningtextiel.

Vervuiling van oppervlakken bevordert de groei van schimmels. Slechts weinig groei werd gezien na 40 weken incubatie van schimmel-diasporen op schoon gipsplaat en dito vurenhout. Schoon tapijt en matras bleef zelfs vrij van schimmelgroei onder deze condities. Het positieve effect van vervuiling op de schimmelgroei bestaat uit het temperen van extreme pH-waarden in het bouwmateriaal en het vergroten van de hygroscopiciteit van het oppervlak (Hoofdstuk 11.1.1).

In de waning worden de oppervlakken onder vochtige condities niet aileen door schimmels, doch ook door mijten en insekten bewoond. Samen met de schimmels vormen deze organismen het ecosysteem van de vochtige muur (Hoofdstuk 11.2.1, 11.2.2, 111.2 en 111.3.). De specifieke soorten die in een woning aangetroffen worden, kan men gebruiken als bio-indicatoren voor de heersende vochtcondities (Hoofdstuk 11.2.1, 111.1).

Huisstofmijten (Pyroglyphidae), voorraadsmijten (Acaridae en Glycyphagi­dae) en andere schimmeleters (Tarsonemini en Psocida) bleken aanwezig te zijn op wanden met een met het blote oog zichtbare schimmelbegroeiing. De betreffende schimmels bleken te behoren tot de zogenaamde xerofiele (bijvoor­beeld Aspergillus penicilloides) en mesohygrofiele soorten (bijvoorbeeld Clados­porium herbarum). Gezien vanuit mijten en stofluizen (Psocida), vormen de schimmels een voedselbron. Het voordeel voor de schimmels is gelegen in het verspreiden van hun sporen door mijten en insekten. Dit betekent overigens niet dat de mijten aileen voorkomen b!j met het blote oog zichtbare schimmelgroei. Ook een microscopisch dunne laag van mycelium (onzichtbaar voor het blote oog) geeft de geleedpotigen voldoende voedsel (Hoofdstuk 11.2.1 ).

Niet aile mijten op de wand zijn van schimmelgroei afhankelijk. Er stuiven voldoende huidschilfers van mens en huisdier uit woningtextiel, lijf- en linnen­goed tegen de wand om een behoorlijke populatie van huisstofmijten te voeden. Er bestaat dan ook een positieve correlatie tussen de huisstofmijtenaantallen in woningtextiel en op de wand. Deze relatie is niet gevonden voor de van schimmelgroei afhankelijke soorten (Hoofdstuk 11.2.3).

Huisstofmijten en voorraadsmijten verschillen verder in de mate waarin zij guanine uitscheiden in hun uitwerpselen. In het geval van de huidschilfer-etende huisstofmijten bestaat er een kwantitatieve relatie tussen de aanwezige aantal­len en de guanine-uitscheiding. Deze relatie is afwezig bij de schimmelvretende voorraadsmijt Glycyphagus domesticus. Het verschil in voedselrelatie zal de oorzaak zijn van het gevonden verschil. Wanneer het guanine-gehalte van het stof wordt gebruikt als maat voor de blootstelling aan mijten in huis, zal dit onder extreem vochtige omstandigheden leiden tot een onderschatting van het allergoloische probleem (Hoofdstuk 11.1.2.).

Andere methoden om blootstelling aan mijtenprodukten te meten zijn het tellen van de mijten in het stof en het bepalen van de mijtenallergenen in dit medium of in de Iucht.

Het huisstofmijtenallergeen Der p I bleek onder gesimuleerde woningcon­dities bijzonder stabiel te zijn. Zelfs na ongeveer 4 jaar was zijn activiteit niet verminderdl Voor de allergologische woningsanatie betekent dit dat niet aileen

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de mijten gedood moeten worden, doch dat vervolgens oak het allergeenrijke stof verwijderd dient te worden (Hoofdstuk 11.1.3.).

Gezien de grotere vochtigheid binnenshuis en het gebruik van meer natuurlijke materialen, werd het woningtextiel v66r de tweede wereldoorlog voornamelijk door voorraadsmijten bewoond. De aantallen waren hager dan tegenwoordig. In die tijd werden huisstofmijten vooral in vogelnesten gevonden en op gedroogde huiden. Het klassieke saneren van deze woonomgeving bestond uit het verwijderen van (al) het woningtextiel. Klinisch bleek dat zeer effectief te zijn. Na de tweede wereldoorlog is het in eerste instantie droger geworden in huis. Bovendien nam de hoeveelheid synthetische materialen toe. Onder deze omstandigheden verdwenen de voorraadsmijten vrijwel volledig in stadshuizen en rukten de huisstofmijten op. Laatstgenoemden werden de meest abundante geleedpotigengroep binnenshuis. De laatste jaren stijgt de vochtigheid in onze huizen weer, als gevolg van energiebesparende maatrege­len. Meer voorraadsmijten en schimmels binnenshuis is het gevolg. De allergie voor voorraadsmijten heeft zich opnieuw uitgebreid naar de stad.

Voordat een succesvolle allergologische woningsanatie uitgevoerd kan worden is enig voorwerk vereist. In geval van de waning van een eczeem­patiente, die een overgevoeligheid had voor voorraadsmijten, schimmels en huisstofmijten, zijn drie verschillende technieken benut om daadwerkelijke blootstelling vast te stellen: mijtenanalyse van opgezogen stof, luchtbemonste­ring met open petri-schalen en microscopische analyse van plakbandafdrukken van de wanden. Vooral voorraadsmijten en schimmels bleken aanwezig te zijn; huisstofmijten kwamen vee! minder voor (Hoofdstuk 111.2.).

Nadat de genoemde inventarisatie in deze vochtige waning (binnen­klimaatklasse IV) was uitgevoerd en de resultaten bekend waren, is door biologische, medische en bouwkundige experts samen met de huisgenoten een op deze situatie toegesneden sanatieprogramma opgesteld. De huisgenoten en hun familieleden voerden dit plan zelf uit, onder supervisie van de experts (Hoofdstuk 111.2.).

Het programma bestond uit korte-termijn maatregelen die weliswaar snel effect sorteerden, doch regelmatig herhaald moesten worden, en lange termijn maatregelen. Het korte-termijn-plan bestond uit het regelmatig wassen van woningtextiel, het gedeeltelijk verwijderen en gedeeltelijk reinigen van niet­wasbare, doch wei ge'infecteerde materialen. De lange-termijn maatregelen betroffen de aanschaf van volledig wasbare matrassen, hoofdkussen en dekbedden, een verbetering van de ventilatie en het verlagen van de vochtig­heid in huis. De maatregelen leidden tot een langzame daling (gedurende enkele jaren) van het totaal lgE in het serum van de patient, en een langzaam verdwij­nen van de huid- en longklachten van de patient. Bovendien was de patient weer in staat haar werk te hervatten (Hoofdstuk 111.2.).

In twee drogere woningen (op het grensgebied van binnenklimaatklasse II en Ill) kon het sanatieprogramma simpeler zijn. De vochtbestrijdingscomponent is weggelaten. De korte-termijn maatregelen bestonden uit een speciaal reini­gingsprogramma (met een acaricide-reinigingsmiddel) en het gebruik van mijten­en allergeendichte hoezen om de matras, alsmede het gebruik van wasbare

, dekbedden en kussens. Deze korte-termijn maatregelen leidden niet tot een klinische verbetering van het eczeem bij aile drie de patienten, hoewel de mijtenblootstelling (gemeten als guanine in het stof) wei daalde. Aileen de patient met ernstig eczeem ondervond een klinische verbetering als gevolg van de genomen maatregelen. Er bleek wei een relatie te bestaan tussen blootstel­ling aan mijten (guanine) en symptomen. De behandeling met de acaricide­reiniger was aileen in staat de mijtenblootstelling te Iaten dalen in textiele

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vloeren die hevig besmet waren. De mijtendichte hoezen en het regelmatig wassen hield de blootstelling wei beneden de internationale hygienische grenswaarde (0,6 mg guanine per gram afgezogen stof}. De huisgenoten beschouwden het wassen echter als zeer belastend en voerden het niet voor al het textiel regelmatig uit. De minder frequent gewassen zaken vertoonden daarna een waarde boven de hygienische grenswaarde. Wellicht had ook in deze, bouwkundig gezien, droge woningen een vochtbeperkingsplan uitgevoerd moeten worden en had rekening gehouden moeten worden met individuele drempelwaarden wat betreft de mijtenblootstelling (Hoofdstuk 111.3.}.

Onder vochtige omstandigheden vormen de wanden in huis een groot allergeen-accumulerend oppervlak. Dit oppervlak wordt bewoond door schim­mels, schimmeletende mijten (Tarsonemoidea, Glycyphagidae, Acaridae} en huisstofmijten (Pyroglyphidae). Daarom dient niet aileen woningtextiel, doch ook de wanden te worden meegenomen in een allergologisch woningsanatiepro­gramma. Bij het opstellen van een sanatieprogramma dient niet aileen het verwachte klinische effect en de technische effectiviteit van de maatregelen in beschouwing geno111en te worden, maar ook de haalbaarheid van de maatrege­len in het betreffende huishouden. Een effectieve sanatie hoeft niet arbeidsin­tensief te zijn en kan gemakkelijk uitgevoerd worden. Tenminste, wanneer daarmee bij het ontwerpen en detailleren van woningen en bij renovatie reke­ning is gehouden.

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CURRICUlUM VITAE

Helianthe Sherida Marianne Kort was born on 23 July 1962 in Paramaribo, beneath the Surinam sun. In 1982 she obtained the Athenaeum B diploma at the Herman Jordan Lyceum in Zeist. She completed her Master's course in Biology in 1987 at Utrecht University, specialising in Medical Biology. In that same year she earned the grade-one teaching qualification in Biology.

From 1988 to 1994 she was assistant researcher ("toegevoegd onderzoeker") at the interuniversity task group 'Home and Health' of Utrecht University and Eindhoven University of Technology. She specialised in allergological home sanitation and was involved in the developing of allergological avoidance programmes. Both fundamental as well as applied research in the field of the biology of the indoor environment were her interests, with the inventory, isolation and determination of mites and fungi forming essential parts.

She has been secretary of the Association of Suppliers of Sanitation Products and Services (VlS) since april 1994. In June 1992 she married lucien Veldema and in January 1994 their son Felicien was born.

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STELLING EN

Een huis zonder schimmel, mijt of stofluis op de muren, is als een woning zonder prenten aan de wand.

II Selectieve sanatie is effectief in het verminderen van allergische symptomen, doch de patient blijft ook verantwoordelijk voor het vermijden van pollen en voedselallergenen.

Ill Binnen se!ectieve sanatie is het verwijderen van mijtenallergenen uit de reser­voirs een 'must', daar het allergeen minstens 4 jaar lang aanwezig blijft. Dit proefschrift, hoofdstuk 11.1.3~

IV Schimmels, mijten en andere geleedpotigen kunnen dienen als biologische sensoren voor fysische factoren, zoals vochtigheid. Dit proefschrift, hoofdstuk 11.2.1.

v Promovendi en zwangeren Ieven in hun eigen wereld. Een combinatie van beiden leidt tot een extreme isolatie.

VI In vochtige woningen van patienten met een overgevoeligheid voor voorraads­mijten en I of schimmels dienen de muren te worden onderzocht en eventueel behandeld, aangezien deze een groot allergeen-accumulerend oppervlak hebben. Dit proefschrift, hoofdstuk 111.2

VII De integratie van allochtonen in de Nedertandse samenleving loopt met dezelfde snelheid (in jaren) als de groei van schimmels op 'schone'-ondergronden bij een relatieve vochtigheid < 75% (in weken).

VIII Conventionele sanatie leidt, op z'n best, tot een tijdelijke verlichting van de allergische klachten, terwijl selectieve sanatie in de allergeenrijke woning, als korte-termijn maatregel, gecombineerd met het uitdrogen van de woning, als lange termijn maatregel, leidt tot een permanente vermindering van de allergeen expositie en tot een vermindering van de allergische klachten. Kniest eta!. Clin Exp Allergy vo/21; 39-47; 1991. Dit proefschrift, hoofdstuk Ill.

IX Een grenswaarde van 1 0 tot 16 schimmelkolonies per plaat (0 10 em), verkre­gen met de open-plaat-methode, zou kunnen gelden als een richtlijn, waarboven schimmel-reducerende maatregelen genomen dienen te worden. Prahl P. Allergy vo/47; 362-365; 1992.

X De IS0-9000 serie kwaliteitstandaard als referentie bij de beoordeling van kwaliteit voor onder meer agrarische produkten, richt zich te weinig op de oplossing van praktische problemen die ondervonden worden door expor­terende ontwikkelingslanden.

XI Technisch effective sanatie-maatregelen resulteren aileen in een klinisch succes als ze ook haalbaar zijn in de praktijk. Dit proefschrift, hoofdstuk Ill.

XII De bijdrage van kauwgum aan vervuiling van de stedelijke omgeving is evident; maatregelen om deze terug te dringen verdienen derhalve meer aandacht.

Stellingen behorend bij het proefschrift: "A structured approach to allergen avoidance in dwellings, with special emphasis on the ecosystem of humid indoor walls and room partitions".

Zeist, 30 november 1994 Helianthe S.M. Kort