ORIGINAL ARTICLE

Trichodectes canis in puppy and adult dogs

Danieli Brolo Martins & Emanuele Zanella de Oliveira &

Marilia Avila Valandro & Miryâne Franco &

Janaína de Souza

Received: 14 June 2013 /Accepted: 19 August 2013# Springer-Verlag London 2013

Abstract One cause of pruritus in dogs is pediculosis, adisease transmitted by the high infestation of lice. We reporttwo cases of pediculosis by Trichodectes canis in differentstages of life: in a puppy dog and in an adult dog. In the firstcase, a female Chow Chow puppy dog, 2 months old, waspresented showing clinical signs such as incoordination, poorbody status, tangled hair in the ventral thoracic and abdominalarea, pruritus, intense skin flaking, and seborrhea and seba-ceous secretion besides fleas and lice. In the other case, anadult female Cocker Spaniel dog was attended, 8 years old,with severe itching, weight loss, listlessness, erythema in theabdominal area, neck, and ears, and presence of lice. Thetreatment for pediculosis caused by T. canis is simple, basedon the application of fipronil spot-on. Thus, the veterinarypractitioner should be aware of diseases that demonstrateseborrhea and pruritus, and include the infestation by T. canisin the differential diagnosis.

Keywords Pediculosis . Chewing lice . Pruritus .

Ectoparasiticides . Canine

Introduction

Dermatology is one of the most representative areas in smallanimal clinic, making up about 20 to 75 % of medical con-sultations (Scott et al. 2001). Some of the factors that contrib-ute to high number of dermatologic cases are the visualizationof skin alterations by the owner (Souza et al. 2006) and/or

changes in the animal behavior, such as intense itching, lead-ing to self-injury (Araújo 2001).

In this sense, one of the causes of itching is pediculosis, adisease transmitted by the high infestation of lice (Araújo2001; Medleau and Hnilica 2009; Wall and Shearer 1997).In addition to constant and irritating prague, these insects arelinked to constant epidemics and secondary diseases (Cezar2005).

Pediculosis may be caused by chewing or sucking of host-specific parasites (Medleau and Hnilica 2009). Lice are insectsbelonging to either the Anoplura order for sucking lice orMallophaga order for chewing lice, such as Trichodectescanis (Phthiraptera, Ischnocera). Chewing lice feed crusts,secretions, and other skin organic materials (Hargis andGinn 2009; Sloss et al. 1999).

T. canis is a constant ectoparasite with a typical life cycle,including an incomplete metamorphosis. The eggs are at-tached to the dog's hair shafts and after 5–8 days they giverise to three nymphal stages, followed by a reproductivephase. The full cycle takes 3 to 5 weeks (Wall and Shearer1997).

The domestic dog (Canis familiaris ) is considered theprimary host of T. canis . In addition to this, this louse hasalso been observed in wild canids (Badr et al. 2005; Jimenezet al. 2010; Gardner et al. 2013). However, it is a disease witha higher incidence in young neglected animals (Medleau andHnilica 2009). However, T. canis is not always found in areaswith high density of ectoparasites, such as Rhipicephalussanguineus (Dantas-Torres et al. 2009).

The T. canis causes irritation to the hosts, which makethem become restless, do not feed or rest properly, and scrubthemselves so intense with their paws or mouth. This actioncan result in tearing of hair, damaging of the skin, and causinginjuries that may be aggravated by secondary infection (Cezar2005; Jimenez et al. 2010). Moreover, desquamated cell plug(Araújo 2001), seborrhea, tangled hair, small papules, crusts

D. B.Martins (*) : E. Z. de Oliveira :M.A. Valandro :M. Franco :J. de SouzaUniversity Veterinary Hospital, Center of Health Sciences,University of Cruz Alta, Cruz Alta, Rio Grande do Sul98005-050, Brazile-mail: vetdanielimartins@yahoo.com.br

Comp Clin PatholDOI 10.1007/s00580-013-1810-9

and, in more severe cases, weakness and anemia can also beobserved (Medleau and Hnilica 2009).

Although they have a great capacity for proliferation, theseectoparasites do not survive more than a few days away fromthe environment of the host and are transmitted by directcontact with infected animals, as well as brushes, combs,bedding, pillows, and other objects (Medleau and Hnilica2009; Sloss et al. 1999).

In terms of control, the oldest ectoparasiticides demonstrategood efficacy against adult lice but do not have a goodovicidal activity and/or persistent, leading to the need forfrequent treatments to eliminate new emerging nymphs(Pollmeier et al. 2002).

Currently, newly developed products, with low volume,applied topically or systemically, although not always labeledfor specific claims against lice, may offer safer alternatives,being more effective and convenient (Nolan and Lok 2012;Arther 2009), such as fipronil (Pollmeier et al. 2002; Arther2009), selamectin (Shanks et al. 2003), and the associationbetween imidacloprid and moxidectin (Kim et al. 2008).

Some ectoparasites has its detection, identification, andcontrol quite easier. However, others can be a challenge tothe professional (Arther 2009). Thus, this paper aims to reporttwo cases of pediculosis by T. canis in different stages of life,in a puppy dog and in an adult dog. Since pediculosis is anuncommon disease in dogs and cats (Medleau and Hnilica2009; Pollmeier et al. 2002), the veterinary practitionershould be aware of the diseases that show seborrhea anditching, and include the infestation by T. canis in thedifferential diagnosis.

Report case 1

A Chow Chow female dog, 2 months old, with no history ofvaccination or anthelmintics was presented at the VeterinaryHospital of the University of Cruz Alta (HV-UNICRUZ). Inthe interview with the owner, he reported that the animal wasshowing uncoordinated movements, disability to feed itself,and an episode of vomiting with parasites. The owner alsoreported that he had gotten the animal on the same day of themedical consultation, and that his puppy was the smallest andweakest of the litter. The animal lived in an open courtyardwith several dogs of different ages, without special care, andwith unrestricted entry of strange dogs.

During the physical examination, the alterations observedwere incoordination, mild degree of dehydration, pale mucousmembranes, normal body temperature, poor body status, tan-gled hair in the thoracic and abdominal ventral regions, pru-ritus, intense desquamated cell plug, diffuse dry seborrhea,and sebum secretion. Epidermal collarettes and pustules onthe ventral abdomen were also observed, along with

ectoparasites. On closer examination, fleas and lice wereobserved in the patient (Fig. 1), ratified by microscopicevaluation.

Other materials were also collected, as blood for completeblood count (CBC), as the nervous clinical signs presentedcould be compatible with distemper or release of neurotoxinsof Toxocara sp. Feces were collected from the rectum for stoolexaminations.

The microscopic evaluation identified species of louse asT. canis (Fig. 2). The stool examinations revealed Toxocaracanis . The CBC already revealed no changes in leukocytecount, but moderate microcytic hypochromic anemia wasobserved in the erytrogram.

After obtaining the laboratory results, we instituted initialtreatment with fipronil spot-on (Frontline®), single applicationtube for up to 10 kg in weight, applied directly to the neck ofthe dog. We also administered trimethoprim sulfadiazine15 mg/kg, BID, and three consecutive days of membershipfebantel, praziquantel, and pyrantel. Additionally, fluid, com-plex B, antiemetics, and nutritional support for convalescingwere also instituted.

After 1 week of hospitalization, the patient came to death byworsening of nervous clinical signs. The concomitant involve-ment of distemper was later confirmed by histopathology.

Fig. 1 Presence of a louse (arrow) located between the matted hair coatof the Chow Chow dog

Fig. 2 T. canis removed from Chow Chow dog. ×4

Comp Clin Pathol

Report case 2

An adult female Cocker Spaniel dog, 8 years old, with vac-cines and delayed dewormer was presented. In the interview,the owner reported that the animal was being cared by hisdaughter, and the dog was showing weight loss, depression,decreased appetite, itchiness and pain in the body. The animalwas kept in the courtyard, in contact with other dogs and cats,including homeless animals.

The clinical examination revealed normal rectal tempera-ture, pale mucous membranes, normal hydration, and bodyweight of 10 kg. During the dermatological examination,erythema was observed in some portions of the ears, neck,and abdomen, as well as quite secondary infection (Fig. 3).The presence of fleas was observed, but there was a suspicionof the presence of lice (Fig. 4). Samples for microscopicobservation confirmed the clinical suspicion of T. canis .

With the confirmation of the presence of lice, thetreatment was to bathe the animal with pyrethrin-basedshampoo and complete grooming of the animal. Fipronil spot-on (Frontline®) tube for up to 10 kg was also applied in theneck of the animal which should be reapplied in 15 days. Theadministration of cephalexin 500 mg (25 mg/kg, BID,20 days), meloxicam (0.1 mg/kg, SID, 4 days), chlorhexidineshampoo in baths (weekly basis), food supplements and iron-based amino acid, and animal feed supply for dogs withsensitive skin was also shown. The owner was requested toreturn the animal for reassessment after 15 days.

Another recommended action to the owner has been to treatall animals that come into contact with the patient, with the useof fipronil spot-on, as well as treating the environment withpyrethrin.

After 15 days of the initial consultation, the animal was incontact with the owner who reported that the animal wasbetter, eating well, and very active. The skin lesions hadregressed and there was no itching.

Discussion

The dogs have often a variety of ectoparasites, among theseare lice, which can result in mild to severe consequences,depending on the rearing conditions, severity of infestation,as well as the nature of the defense mechanism (localized orsystemic) mobilized by the host in response to the parasite(Arther 2009). In this aspect, animals of different ages, i.e.,puppies and adult dogs, may present some particularitiesrelating to the clinical signs of pediculosis.

Domestic dogs and wild animals can be infested with twotypes of biting lice: T. canis or Heterodoxus spiniger (Badret al. 2005; Linardi 2001). In both reported cases, the animalshad a single species of Mallophaga, T. canis . Although thediagnosis by direct visualization is possible, the Chow Chow'sdirty and intensely matted hair coat made such a view difficult.In the case of the Cocker Spaniel, direct visualization waspossible only after shaving the hair. Immediate microscopicevaluation (since lice are very mobile) was essential for thecorrect identification of the parasite (Medleau and Hnilica2009; Sloss et al. 1999).

Most of the problems related to this ectoparasite is associat-ed with irritation and itching. The cause of pruritus is stillunknown but is believed to result in more than just mechanicalirritation (Hargis and Ginn 2009). Besides that, dog lice aredifficult to diagnose by the naked eye unless specificallysearched for (Jimenez et al. 2010). In addition, our ChowChow patient had concomitant infestation by Ctenocephalidescanis , an ectoparasite quite common and can easily lead to amisdiagnosis, as found in similar locations to T. canis and leadsto the appearance of many similar clinical signs. Scabies,cheyletiellosis, and hypersensitivity reactions should also beincluded in the differential diagnosis (Wall and Shearer 1997).

The favorite regions of parasitism include the head, neck,back, and tail region. The T. canis is highly active. It feeds onthe flaking and secretion from the skin wounds. The excessiveitching leads to the matted, alopecic lesions and developmentof crusts, as well as abrasions and secondary bacterial involve-ment (Medleau and Hnilica 2009; Wall and Shearer 1997;

Fig. 3 Erythema and secondary infection in the abdomen of the CockerSpaniel dog

Fig. 4 Presence of many lice (arrows) in the Cocker Spaniel dog

Comp Clin Pathol

Arther 2009). Our patients had several of these lesions.However, it is likely that some of these lesions, such aspustules and epidermal collarettes on the abdomen, are dueto dermatologic phase distemper presented by Chow Chow.Still, it is interesting to note that the intense itching, and thelesions that this act entails, can cause a framework of stress onthe animal causing it to feed less, leading to weight loss. Theclinical symptoms must be distinguished from dermatitis al-lergy to flea bites in a first moment, especially in adult animalsthat have low infestation by lice. However, animals with lowinfestation may show no clinical signs or lesions (Hargis andGinn 2009).

Another factor common to these two ectoparasites is thatthe T. canis can also serve as an intermediate host of cestodesDipylidium caninum parasite in dogs (Wall and Shearer 1997,Cardozo et al. 2003) and occasionally in humans (Sloss et al.1999). In the Chow Chow dog, feces were examined and nointestinal cestode was found.

Moreover, while the pulicosis occurs especially in warmtemperatures (Sloss et al. 1999), pediculosis usually occurs inwinter, when temperatures are colder, the coverage pilosa islonger, the animals are gathered, and nutrition is lower (Hargisand Ginn 2009; Jimenez et al. 2010). Despite the low temper-atures of Brazilian South winter (subtropical weather) duringthe Chow Chow patient's care, it was still possible toobserve the significant presence of fleas along with thelice. This fact emphasizes the importance of a more de-tailed examination of the coat, since lice can go unnoticed.In addition to this, the worsening of anemia presented bythe animal, typical of iron deficiency anemia, could beoriginated by the action of fleas (Araújo et al. 1998), aswell as the chewing lice, since they can ingest blood fromwounds (Sloss et al. 1999).

Ages and immune states of patients reported are in agree-ment with the literature citing the infestation by T. canismainly in younger, senile, debilitated (Pollmeier et al. 2002),neglected and malnourished animals (Medleau and Hnilica2009). Toxocariasis added distemper, which may have con-tributed to the severity of the patient in case 1. However, it isimportant to remember that the decrease in hygiene and in-creased infestation could be related, but not as cause andeffect. Both would result from a single cause: the neglect ofthese animals.

It is very important to treat affected animals and those ofthe same species that had contact with them; this was alsorecommended to the owner of the Cocker Spaniel. It should bepointed out to the owners that lice should not be killed directlywith nails, because their blood can be contaminated andtransmit various diseases if there are cuts or sores on the skin(Linardi 2001).

The lice infestations are usually treated with dust, aerosolsprays, liquids, or shampoos. The treatment is often repeatedin a range of 14 to 30 days to kill newly hatched lice (Medleau

and Hnilica 2009; Pollmeier et al. 2002; Urquhart et al. 1998).Already a spot-on version may require only a single applica-tion (Arther 2009). Traditional treatments include calciumsulfide, 2 % pyrethrin, pyrethroid, organophosphate, and car-baryl. Ivermectin, selamectin spot-on (Medleau and Hnilica2009), imidacloprid 10%+2.5 % moxidectin spot-on (Kimet al 2008), and 0.25 % fipronil spray or 10 % spot-on(Medleau and Hnilica 2009; Pollmeier et al. 2002) are alreadyconsidered as alternative treatment; the latter being used inthis case. Death of most parasites was observed 24 h afterapplication of the product, with the complete elimination ofhead lice 48 h after the application.

For prophylaxis, collars are often used with a carbamate-based insecticide or pyrethroid insecticide diazinon (Urquhartet al. 1998).

Taking into account only the lice, the prognosis is generallygood (Medleau and Hnilica 2009; Jimenez et al. 2010;Gardner et al. 2013). Despite the success of treatment againstT. canis , Chow Chow's clinical case progressed to death dueto distemper and its complications. The case study of CockerSpaniel described the full success of the treatment given to theanimal, having significant improvement in 2 weeks oftreatment.

In conclusion, the pediculosis can sometimes go unnoticedby both the owner and by the veterinary practitioner.Therefore, the infestation by T. canis must be taken intoaccount in the differential diagnosis of seborrhoea andpruritus in dogs. Young animals, malnourished with con-comitant diseases (viruses or endoparasitosis), or neglectedas observed in these cases, are more susceptible to this kindof disease. Prevention and control measures should betaken to the contacts of the same species, as well as actionsto hygienic environment.

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