1

Abstract:

Penicillium marneffei is a dimorphic fungus that causes fatal systemic mycosis in

immunocompromised patients. The infection Penicilliosis marneffei occurs most

commonly in HIV patients and is currently endemic in South East Asia. The instance

of P. marneffei infection has risen substantially due to the AIDS endemic and has a

100% mortality rate in untreated patient. P. marneffei is the only thermally dimorphic

fungus within its species, producing hyphal growth at 25°C and unicellular yeast

growth at 37°C.

The ability to grow at 37°C facilitates its infectivity in humans. P. marneffei primarily

affects the pulmonary system, disseminating through the blood to other internal

organs. Primary symptoms include weight loss, fever, anaemia and skin lesions

which can be successfully treated with a course of Amphotericin B followed by

Itraconazole. P. marneffei has been successfully extracted from the internal organs

of bamboo rats, however the current mode of transmission into humans is unknown.

It is commonly believed that infectious conidia are inhaled from an environmental

source possibly from the soil. In order to successfully control rates of infection, the

ecological niche of P. marneffei must be uncovered to understand transmission

methods. More interest is required in discovering the environment and the

epidemiology of P. marneffei to reduce the number of fatalities caused by

Penicilliosis infection.

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1. Introduction:

1.1. Penicillium marneffei:

Penicilliosis marneffei is described as an opportunistic and progressive infection

induced by the fungus Penicillium marneffei. P. marneffei is currently the only known

thermally dimorphic fungus within the Penicillium genus that causes fatal systemic

mycosis in immunocompromised hosts. Patients suffering from human

immunodeficiency virus (HIV) are the most common immunocompromised patients

affected. The infection is currently endemic in South East Asia including Southern

China, Vietnam, Thailand, Taiwan and Hong Kong with the number of instances

increasing due to the prevalence of AIDS in these areas. In northern Thailand, the

disease is ranked third following tuberculosis and cryptococcosis as the most

common opportunistic infection in patients suffering from HIV (Supparatpinyo et al.,

1994).The transmission method of P. marneffei is unknown, however it is suspected

that the infection is transmitted through inhaled conidia produced by an

environmental form of the fungus (Kaewmalakul et al., 2014).This project will discuss

the biology of P. marneffei infection including the mycology, pathology, diagnosis

and treatment of infection. The epidemiology of the infection including possible

reservoirs and methods to control P. marneffei will also be discussed in detail.

1.2. History:

The first isolation of P. marneffei occurred in 1956 from hepatic lesions extracted

from a bamboo rat’s liver (Rhizomys sinesis) at the Pasteur Institute of Indochina,

Vietnam (Segretain 1959). The fungus was named Penicillium marneffei, recently

changed to Talaromyces marneffei (Samson et al., 2011), in respect to Hubert

Marneffe, Pasteur Institute director in Indochina and Paris. The first reported

incidence of P. marneffei in humans occurred in 1959 when the researcher G.

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Segretain accidently inoculated the fungus into his finger in the laboratory (Segretain

1959). This caused the formation of a nodule after 9 days and also the development

of lymphadenopathy which was successfully treated with oral nystatin (Deng et al.,

1988). In 1973, the group of researchers including DiSalvo reported the first natural

human infection of P. marneffei from a patient living in North Carolina (DiSalvo

1973). The 61 year old minister reported he had worked in Vietnam and was treated

for Hodgkin’s disease where his spleen contained isolates of P. marneffei (Duong

1996). Another 5 cases where reported in 1984 by Jayanetra, in Bangkok (Jayanetra

et al., 1984). From these patients, 2 who had no underlying conditions were treated

with amphotericin B successfully, however the remaining three patients were

misdiagnosed with tuberculosis and died as a result. In the preceding years eight

cases where reported in China with a further 20 cases in the Guangxi region and six

cases reported in Hong Kong (Vanittanakom et al., 2006). The very first reported

incidence of penicilliosis marneffei in a HIV infected patient occurred in 1988 by Piehl

and colleagues causing severe mycosis. Due to the exponential rise in the

prevalence of HIV in Asia, the instance of P. marneffei has risen markedly as these

patients have a high susceptibility to infection (Piehl et al., 1988). Due to the high

frequency of P. marneffei among immunocompromised patients, the infection is now

recognised as an AIDS-indicating disease in many areas including Hong Kong and

Thailand (Cánovas & Andrianopoulos 2007).

1.3. Patients Affected:

HIV positive patients are those mainly infected with penicilliosis due to a weakened

immune system. Infection has been reported in patients who were not HIV positive or

immunocompromised however this instance is rare. A review of the instances in

mainland China from 1984 to 2009 demonstrated that 87.72% of the cases treated

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were HIV positive (Liu et al., 2013). Prior to the HIV endemic the instance of P.

marneffei infection was relatively rare with only a few cases being described (Lee et

al., 2014). In the Chiang Mai hospital in Thailand, there were 1,115 cases of P.

marneffei infection between 1990 and 1997 alone (Sirisanthana et al.,1998). P.

marneffei infection has been recorded in HIV negative patients that have other

underlying conditions such as tuberculosis, Hodgkin’s disease, systemic lupus

erythematosus, patients recovering from immunosuppressive therapy and even

alcoholism (Wong et al., 2001).

2. Biology:

2.1.Mycology:

Figure 1. (Vanittanakom et al., 2006): Morphologies of P. marneffei species seen

under the microscope. In (A) the hyphal form can be seen with phialides and conidia.

In (B) the cells begin hyphal formation showing branched filaments. In (C) hyphae

have completed arthroconidiogenesis at 37°C. In (D) the yeast cells can be viewed

after incubation at 37°C.

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The Penicillium group of species is comprised of over 200 fungal species. P.

marneffei is regarded as one of the few species with medical importance within its

genus (Andrianopoulos 2002). The infection is also currently the only fungus within

the Penicillium genus that has been described as a temperature-dependent

thermally dimorphic fungus. At 25°C colonies can be cultured which are filamentous

in form and at 37°C the pathogenic form is expressed as oval shaped unicellular

yeast cells. The lifecycle of the infection is separated into three distinct phases: at

25°C there is filamentous hyphal growth, also at 25°C asexual development

(conidiation) can be seen and at 37°C unicellular yeast growth can be seen

(Kavanagh 2007).

Under suitable nutritional conditions at 25°C, the germination of a conidium occurs

within the first 6 hours through isotrophic growth, forming downy grey colonies and

by 12 hours a germ tube is produced through polarised growth. The germ tube

continues to grow through polarised growth at the apical tip for the formation of a

hypha and through septation cellular compartments are established behind the

apical tip. These sub-apical cells can produce branched cells with a new growth

point through repolarisation. The uncoupling of nuclear and cellular division occurs

where compartments of the actively growing cells contain multiple nuclei

(Andrianopoulos 2002).

In P. marneffei, yeast morphogenesis can occur at 37°C where yeast cells that can

divide by fission, are produced. The ability to grow at 37°C facilitates its infectivity in

humans (Kaewmalakul et al., 2014). Morphogenesis begins 48 hours after

germination giving rise to branched uninucleate hyphae through the coupling of both

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nuclear and cell division. Hyphal segment that consist of single nuclei are produced

and these pre-arthroconidial cells are easily separated by double septa. The

degradation of material that lies between the double septa occurs after time, the

process of arthroconidiation. These cells can assist the maintenance of the

elongated cell shape, initiate polarised growth and following nuclear division they

divide by fission to produce true yeast cells. The resulting yeast cells are also

capable of dividing by fission at 37°C however, yeast cells grown in vivo have a

different morphology than those in vivo (Cánovas & Andrianopoulos 2007). When

hyphae that have been produced at 25°C enter a temperature of 37°C they can

initiate a comparable morphogenic process that begins with coupling of nuclear and

cell division in the apical cells. This dimorphic transition can be reversed by

decreasing the temperature back to 25°C allowing the uncoupling of nuclear and

cellular division and the yeast cells are polarised forming hyphal cells.

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Figure 2. (Andrianopoulos 2002): Representation of the P. marneffei lifecycle

including asexual development and dimorphic switching. At 25°C the fungus grows

as a mycelial through hyphal growth and asexual development can produce conidia.

At 37°C the fungus grows as pathogenic yeast cells that divide by fission.

P. marneffei can also initiate asexual development which leads to multicellular

conidiophores containing uninucleate conidia. This process occurs after hyphal

growth at 25 °C and requires specific environmental conditions including light and an

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air interphase. This process begins with the production of multinucleate aerial stalk

cells from specialised hyphal cells. These stalk cells can be septate, they grow

outward from the mycelium and can produce secondary stalk cells known as rama.

At the stalk cells tips, budding division occurs producing two layers of uninucleate

sterigmata cells known as the phialides and the metulae. On the stalk there can be

found usually 3-5 metulae and by an acropetal mode of division each metula can

produce 3-5 phialides. A chain of spores is produced from the phialides through

basipetal division, where younger spores displace the old spores. The conidia are

oval, often have prominent disjunctors and mature spores can be identified by the

grey-green pigment they produce (Deng et al., 1988). There are a variety of

regulatory genes that play vital roles in the control of asexual development and the

control of dimorphic switching (Yang et al., 2014). The regulatory gene abaA plays

an important role in controlling cell cycle events during coniditation and during yeast

growth. AbaA deletion strains produce stalks, rama and metulae that are incapable

of producing spores. The stuA regulatory gene also plays an important role in

asexual development as deletion of the gene result in loss of production of metulae

and phialides. GasA is a signalling gene that results in delayed conidiation and is

majorly involved in the switch from growth to development. Dimorphic switching in P.

marneffei is also controlled by abaA gene which affects the coupling of the nuclear

and cell division cycles in yeast cells. The homologue cflA is also important during

dimorphic switching as it is required for correct morphogenesis of yeast cells

(Andrianopoulos 2002). A study in 2014 suggests that the yakA gene of the fungus

has a vital role in normal growth and development as yakA mutant strains exhibited

abnormal morphogenesis (Suwannakorn et al., 2014). The study of the dimorphic

switching in P. marneffei has increased the understanding of the control mechanisms

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in other fungal pathogens. Understanding the biology of P. marneffei can provide

targets for drugs used during treatment of infection.

2.2. Pathology:

P. marneffei is a pathogen that primarily affects the pulmonary system and has the

ability to disseminate hematogenously through the blood to other internal organs.

The immunological state of the host has a major effect on the severity of the disease

(Vanittanakom et al., 2006). It is evident that the pathogenicity of the fungus is

closely related to the dimorphic transition from the mycelial phase in the

environment, to a yeast phase within the host (Suwannakorn et al., 2014). P.

marneffei initially invades the host through the skin or possibly through inhalation

and the yeast cells penetrate the macrophages. P. marneffei conidia can kill

macrophages and disseminate through the body. To ensure survival of the conidia

within the phagocytes, the fungi responds to the host environmental stresses by a

mechanism that is still unknown (Nimmanee et al., 2015). The disease can cause

three different reactions within a host, a granulomatous reaction, a suppurative

reaction and an anergic and necrotizing reaction (Deng et al., 1988). In

immunocompetent patients, granulomatous reaction can be seen in organs of the

reticuloepithelial system where a granulomas is formed by histiocytes, lymphocytes,

plasma cells and epithelioid cells. The yeast cells multiple intracellularly causing the

granulomas to enlarge and proliferate to accommodate the fungal cells. The centre

of the granulomas becomes necrotic as it continues to enlarge causing the

accumulation of neutrophils and the formation of an abscess.

The suppurative reaction commonly occurs in immunocompetent patients causing

multiple abscesses in organs such as the lung, liver, skin and subcutaneous tissue

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by neutrophils and fibrin. Immunocompromised patients are mainly affected by the

anergic and necrotizing reaction in organs such as the lung, skin and liver. Infected

patients show macrophages engorged with proliferation yeast cells which can be

used as a marker for the presence of a progressive and disseminated infection within

the host. Cultures containing P. marneffei have been isolated from a variety of

organs however the blood, skin, bone marrow, liver, lymph nodes and lungs are the

most common organs targeted (Duong 1996).

2.3. Clinical manifestations:

Figure 3. (Qiu et al., 2014): Chest High resolution tomography showing lung lesions

and protrusions on the wall of the patient’s trachea.

Penicilliosis marneffei infection most commonly causes anaemia, weight loss, fever

and skin lesions in HIV patients. The infection can be characterised by the presence

of skin lesions which can be seen in approximately 85 % of patients mainly occurring

on the face and neck (Vanittanakom et al., 2006). Disseminated infection starts with

fever, chills, coughs and pleurisy (inflammation of the membrane of the lungs).

Hepatomegaly, lymphadenopathy, leukocytosis and arthritis has been reported in

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cases. Over 70% of patients are anaemic and have been recorded with haemoglobin

levels of 10 g/dl or lower. Hepatosplenomegaly is common particularly in children

who are HIV positive and there have been records of bone marrow infection and

genital ulcers (Duong 1996). It is uncommon for the central nervous system to be

affected however there has been reported in Vietnam the development of confusion,

agitation and depressed consciousness in rare cases (Kantipong et al., 1998). A

study in 2013 reported that 10% of penicilliosis patients they examined had P.

marneffei infection in the bone marrow, suggesting bone marrow inspection should

also be considered during treatment (Nong & Liang 2013). The manifestation in HIV

negative patients are relatively similar including the onset of lymoadenopathy,

arthritis, pulmonary infection and osteomyelitis (Wong et al., 2001). These symptoms

are characteristic to other systemic infectious diseases such as tuberculosis,

cryptococcosis and histoplasmosis in patients infected with HIV and may occur along

with penicilliosis (Hilmarsdottir et al, 1993). This makes the diagnosis of P. marneffei

in patients more difficult with misdiagnosis leading to many deaths in the past.

2.4. Diagnosis:

Rapid diagnosis is crucial to begin treatment early and increases the chances of

patient survival (Cao et al., 2009). The diagnosis can be delayed by the slow growth

rate of Penicillium marneffei and its similarities to TB and also non-tuberculous

mycobacterium. The traditional diagnosis method by fungal isolation also requires a

prolonged incubation period. The mould to yeast transition of the infection can be

used as a useful diagnostic tool with the yeast form containing a transverse septum,

which is the marker of binary fission (Jan et al., 2008). The conventional methods of

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diagnosing P. marneffei are through histological examinations under a microscope

and fungal cultures. The isolation of P. marneffei using a microbiological culture is

the most commonly used method with samples taken from the bone marrow, skin,

sputum, papule scrapings, urine or stool samples. Bone marrow specimen has the

highest yield of 100%, with skin samples giving 90% and blood cultures giving 76%

(Supparatpinyo et al., 1994). The fungus can be grown at 25°C on sabouraud

glucose agar, demonstrating its mycelial phase. Through incubation at 37°C there is

a conversion from mold to yeast form which can be used to identify the colony. P.

marneffei culture can be identified through an immunodiffusion technique using

rabbit antiglobulin against antigen from a standard strain. This exoantigen test allows

P. marneffei to be easily distinguished between the other Penicillium species

(Sekhon & Garg 1982). Histological examinations can allow fast diagnosis through

examination of bone marrow aspirates, skin biopsies and lymph node biopsies that

have been Wright-stained. Using stains such as hematoxylin and eosin, periodic

acid-Schiff stain and Grocott methenamine silver can allow the infection to be

examined in cytological studies. P. marneffei is most commonly confused with

Histoplasma capsulatum which also appears as intracellular yeasts and is similar in

regards to size and staining properties (Wong & Wong 2011). The infection can be

examined in the form of unicellular oval cells, which have the ability to separate by

cross wall formation within cells such as machrophages, or extracellular sausage

shaped cells (Vanittanakom et al., 2006). The presence of the transverse septum is

crucial to distinguishing the infection against microorganisms such as Histoplasma

capsulatum. The histological examinations and fungal cultures are very time

consuming methods of diagnosis which may not give a rapid enough diagnosis for

critically ill patients. Cytological examinations have proven to be more efficient at

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producing a rapid response and the specimens can be obtained by less invasive

methods. Cytological studies can be undertaken using specimens from lung

aspirates, sputum, neck lymph node aspirates or lung biopsy imprint smears (Jan et

al., 2008). Cytological smears that are stained by a Romanowsky method can

present the characteristic transverse septum of P. marneffei after aspiration and can

be confirmed by a microbiological culture (Wong & Wong 2011). Serologic diagnosis

has been developed to detect specific antibodies used with antigens of the fungus in

order to provide a swift diagnosis (Vanittanakom et al., 2006) however they are not

widely available. Patients that are HIV positive and are infected with P. marneffei

have a significantly higher level of antigen and lower level of antibody in comparison

to patients who are HIV negative with P. marneffei (Wong et al., 2001). A method for

detecting IgG antibodies using a fluorescent antibody test has been developed using

antigens such as conidia and the yeast form of P. marneffei (Yuen et al., 1994). A

high IgG titer can indicate the presence of infection, suggesting this method has the

potential for rapid diagnosis. Aspergillus fumigatus galactomannan can be detected

using a monoclonal antibody by the PAstorex Aspergillus test kit. This

galactomannan assay can be used to detect galactomannan in P. marneffei using a

specific latex agglutination which increased the sensitivity for penicilliosis detection.

This is a highly specific test which can be utilised for efficient detection and is

currently screened for in newly diagnosed HIV patients (Wong & Wong 2011).

Molecular diagnosis methods for P. marneffei detection have been developed with a

specific PCR assay based on oligonucleotide probe of the 18S rRNA gene. This

method has proven to be highly specific and sensitive, however is a complicated

method of diagnosis (Vanittanakom et al., 2006) and is currently not accessible

during clinical use. In 2011, Zhang et al developed a sensitive method of diagnosing

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P. marneffei by using a multiplex ligation-dependent probe amplification (MLPA)

assay. The group designed three sets of probes used to amplify the internally

transcribed spacer region of P. marneffei rRNA. These probes can simultaneously

detect the gene loci and characterise different fungal strains in the one MLPA

reaction. The MLPA assay is very sensitive and specific and can be completed in

one working day. This method could provide rapid diagnosis and provide information

on the epidemiological studies of the infection (Zhang et al., 2011).

2.5. Treatment:

Figure 4. (Supparatpinyo et al., 1998): Table represents the survival rate of patients

who survived and had no relapse cases during secondary prophylaxis using

Itraconazole and a Placebo. Patients taking Itraconazole had a significantly higher

probability of survival.

The mortality rate of those infected with P. marneffei and are untreated is 100%,

highlighting the importance of swift antifungal therapy (Supparatpinyo et al., 1993).

Due to the high mortality rate, treatment should be administered straight away and

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not delayed until the results from fungal cultures or samples are obtained. P.

marneffei is known to be highly susceptible to the following group of azoles;

itraconazole, miconazole, voriconazole, ketoconazole and fluconazole, with the latter

being the least effective. Itraconazole has a broad antifungal spectrum, low toxicity

level and has appropriate pharmacokinetic properties. Terbinafine and voriconazole

do have some effect against P. marneffei however there is limited data on their

potential use (Liu et al., 2013). Penicilliosis is also susceptible to amphotericin B

which has proven to be effective and is the standard drug for the most severe cases,

however is associated with high rates of relapse (Sekhon et al., 1992). Amphotericin

B requires a prolonged hospital stay which is inconvenient, is relatively toxic, is

expensive and is known to cause adverse side effects. Some of the side effects

include nausea, headaches, vomiting, and it has been associated with multiple organ

damage such as kidney damage (Supparatpinyo et al., 1998). The recommended

treatment is intravenous amphotericin B at a dosage of 0.6 mg/kg taken daily over

the course of 2 weeks, followed by oral itraconazole at a dose of 200mg taken twice

daily over 10 weeks (Qiu et al., 2014). Secondary prophylaxis with itraconazole has

proven to be efficient at preventing relapse in patients who have received the initial

amphotericin B therapy. The strategy of preventing relapse within patients is more

effective than treating patients who have already relapsed (Supparatpinyo et al.,

1998).

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3. Epidemiology:

3.1. Endemic Areas:

Figure 5. (google images): Diagram represents the geographic restriction of P.

marneffei infection to South East Asia. The regions affected may contain similar

environmental conditions for the infection to survive and expand.

P. marneffei infection is currently geographically restricted to Southeast Asia

(Gugnani et al., 2007). There have been confirmed cases of infection outside of the

endemic regions in Europe, North America, Africa and Australia in HIV patients

where they reported no recent travel within Asia. These infected individuals suggests

that the infection only requires short term exposure to be contracted by susceptible

hosts and there must be a minimum of one site of infection within the environment in

these regions where tourist can become infected even during a short stay (Chaiwun

et al., 2011). There are two reported cases of penicilliosis marneffei in patients

outside of Asia who reported no history of travel to the endemic area. The first case

was observed in an African from Ghana in 2000 followed by a case in Togo in 2008,

both in HIV positive patients (Patassi et al., 2013). The mode of transmission for both

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these cases is unknown, however both countries share a border suggesting possible

transmission from the same source. It is suggested that due to the development in

trading between Asian and West Africa, the infection may have travelled by boat.

These cases propose that clinicians should consider P. marneffei in HIV patients that

develop skin lesions, regardless of geographic locations.

The method of transmission of P. marneffei in humans remains a mystery. The

basic ecology of the fungus remains unclear and understanding the ecological niche

of P. marneffei is essential to recovering the mode of transmission. The main issue

of concern is whether penicilliosis marneffei is transmitted by humans through an

animal or environmental source (Vanittanakom et al., 2006).

3.2. Bamboo Rats:

P. marneffei has been successfully extracted from 4 species of rats including

Rhizomys sinensis, Cannomys badius, Rhizomys sumatrensis and Rhizomys

pruinosus, and also from the soil present in the burrows of bamboo rats (Gugnani et

al., 2004). The bamboo rats can be located in the endemic regions, however the

prevalence of infection does vary across Asia (Vanittanakom et al., 2006). There is

little evidence to suggest that humans directly contract penicilliosis marneffei from

these rats, however it is clear that there is a strong association between P. marneffei

and the rodent species (Cao et al., 2011). Infected rats appear healthy, suggesting

that rats are only carriers of the infection (Chaimun et al., 2011). Bamboo rats are

known to live in mountainous regions and have limited contact with humans. Few

humans eat Bamboo rats and P. marneffei cases have been recorded in known

vegetarians (Chariyalertsak et al., 1997). It is widely considered that both humans

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and rats are commonly infected by an external source in the environment, however it

is also considered that the bamboo rats play a role as an obligate phase in the life

cycle of P. marneffei (Cao et al., 2011). Studies suggest that the rats possibly act as

a vector for human infection by acting as amplifiers of the infectious dispersal stages.

Infection within the rodents may benefit P. marneffei as the body of the host, after

death, can create a nutrient rich environment for aerosol dispersal. Both HIV

patients and bamboo rats are reported to have some genetically similar strains which

could indicate possible co-infection from a common source (Chaiwun et al., 2011).

3.3. Soil as a reservoir:

It is currently still unknown the exact mode of transmission within humans, although

it is assumed that infectious conidia are inhaled within the environment and

disseminates through the lungs (Bulterys et al., 2013). In 1997 a case control study

was conducted by Chariyalertsak, (Chariyalertsak et al., 1997) which indicated that

the bamboo rats were not a risk factor of infection, but rather the patient’s exposure

to possible reservoirs in the environment within the soil. The study included data

from 1988 to 1992 and demonstrated that cases were more likely farmers and

labourers and were also more likely to be younger males. The data was not

statistically significant and it is possible that younger people have an increased

chance of exposure to an environmental source through occupation and recreation

(Chariyalertsak et al., 1997). Investigations of soil samples within Asia have been

conducted in order to determine the natural reservoir of P. marneffei. Deng et al.

(1988) were the first group successful at isolating samples from soil taken from R.

pruinosus species burrows. The second successful isolation attempt was made by

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Chariyalertsak et al. (1996) from a soil sample taken from the burrow of R.

sumatrensis species (Gugnani et al., 2004). A study conducted in 2008 (Joshi et al.,

2008) presented findings that in sterile soil, P. marneffei can survive for

approximately 4 weeks and only 2-3 days in non-sterile samples. Other attempts to

isolate P. marneffei from soil samples have failed and there is little evidence to prove

that transmission occurs from the soil.

There is significant evidence indicating increased infection among HIV patients

during the rainy season, particularly in Thailand from May to November. A study from

Vietnam reported a 30 % increase in cases of penicilliosis admitted, demonstrating

the seasonal variation of P. marneffei (Le et al., 2011). These patterns of infection

rates can provide a greater understanding of the epidemiology of the fungus

(Chariyalertsak et al., 1996). The study in Thailand suggested the expansions of P.

marneffei reservoirs may be facilitated by precipitation. As cases of P. marneffei

occur in both urban and rural areas, it is difficult to distinguish where the

environmental source is located. A study in Vietnam examined the association

between penicilliosis cases and environmental variables such as humidity,

temperature, wind speed and precipitation (Bulterys et al., 2013). The study

examined data gathered from the Ho Chi Minh City hospital between 2004 and 2010.

The data demonstrated that precipitation and humidity where strongly associated

with the number of penicilliosis. This data suggests that the combination of both

rainfall and humidity may facilitate spore release or fungal growth in the environment.

It is suggested that rainfall should have a greater influence on fungal growth in soil

located deep in the ground, whereas humidity would facilitate fungal growth on areas

that are more exposed to air. More research into the seasonal variation of P.

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marneffei will lead to greater understanding of the environmental niche and method

of transmission in immunocompromised patients.

The same study from Vietnam also presented findings on the incubation period of P.

marneffei. The strong association between seasonal variations and infection rate

suggests that disseminated disease can occur in a short time after

immunocompromised patients have been exposed to the fungus. Penicilliosis cases

may be due to primary infection, reinfection or reactivation of latent disease

(Chariyalertsak et al., 1997). In cases of penicilliosis within children, primary infection

is the most important problem, with reinfection and reactivation being more important

in adult cases. The study estimates that the incubation period may be between 0 and

3 weeks.

3.4. Possible Reservoirs:

Other possible reservoirs suggested by the case-control study in Thailand are

bamboo plants which are commonly grown and eaten. Bamboo thickets are also the

habitat of R. sumatrensis species of Bamboo rat suggesting that they may possibly

be a common reservoir for infection. Attempts to demonstrate a correlation between

bamboo plants and the infection have not been successful. The possibility of rats

acting as vectors for human transmission suggest that possibly other animals such

as dogs, cats and elephants may play an obligate role in the lifecycle of P. marneffei.

A study in Thailand in 2010 suggested dogs as a reservoir for infection when PCR

samples on nasal swaps obtained from outdoor dogs where positive for P. marneffei

infection. American dogs are known to obtain nasal infections from Penicillium

species and their nasal regions frequently come into contact with nature and soil

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(Mathews & Sharp 2006). The research showed approximately 13% of the dogs that

samples were taken from were positive with P. marneffei. The dogs may be a

reservoir for infection or may just be carriers, more research is required to confirm

these observations (Chaiwun et al., 2011). The presence of P. marneffei within other

animals that frequently come into contact with tourists such as elephants, is

unknown. Studies of these other animals in Thailand would be valuable to

understanding the epidemiology of the infection.

4. Control:

4.1. Methods of Containment:

Figure 6. (Hu et al., 2013): Penicillium marneffei cases have increased exponentially

due to the AIDS epidemic, in the graph a dramatic increase from 2000 to 2009 can

be seen in correlation with the increase in AIDS patients.

It has been noted that in areas where HIV transmission has reduced due to the

introduction of control measures, the cases of P. marneffei have also reduced in

correlation. To effectively control transmission rates of P. marneffei, the prevalence

of HIV must be reduced. There have been numerous projects to help reduced the

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cases of HIV in the developing world. Needle syringe programmes have effectively

reduced HIV and hepatitis C among drug users. The development of sensitive and

specific HIC screening tests have effectively removed HIV infection from the drug

supply in the developed world and these methods could be employed in the

developing world (Bertozzi et al., 2006). To prevent mother to child transmission, a

course of nevirapine can be administered to mothers throughout labour (Guay et al.,

1999). By discovering the ecological niche of P. marneffei, the mode of transmission

may be uncovered which is essential to controlling the infection. Discovering the

mechanisms of infection will prove vital to reducing the total number of infections and

deaths per year. Quicker diagnosis are essential to reducing mortality rates and this

can be achieved by increasing awareness among physicians. In patients with HIV

and P. marneffei, antifungal therapy should not be postponed until the results from

diagnostic tests are obtained (Supparatpinyo et al., 1992).The instance may be

higher than reported due to misdiagnosis in the past and poor reporting of cases in

national statistics, therefore it is essential to adapt controls measures to ensure the

instance decreases (Hu et al., 2013). Shorter treatment regimens that require

reduced hospital stays could decrease the burden on healthcare systems. The cases

in Togo and Ghana suggests that clinicians should consider P. marneffei infection in

all HIV patients presenting with lesions, regardless of geographic regions as only

early diagnosis and treatment can lead to reduced mortality (Patassi et al., 2013).

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5. Conclusion:

The instance of P. marneffei infection has increased rapidly in South East Asia due

to the prevalence of HIV. The mortality rate of HIV infected patients who acquire

penicilliosis marneffei is high if diagnosis and treatment are not rapidly administered.

The epidemiology of the infection is still relatively unknown, however studies have

highlighted possible reservoirs that should be investigated. Transmission of the

infection may not be controlled until the natural reservoir of the infection is

discovered. The cases of infection in Togo and Ghana suggest the infection can

survive in environmental conditions found outside of the endemic regions. More

publicity is required to highlight the significance of the disease in order to increase

interest in studying the infection. This project discusses the infection in detail

regarding the biology, epidemiology and control. The complex morphology of P.

marneffei and the poor understanding of the epidemiology highlight the severity of

infection and the necessity for increased research in order to successfully control it.