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International Journal of Livestock Research
eISSN : 2277-1964 NAAS Score -5.36
Vol 7 (1) Jan’17
Invited Review
Dermatophytosis - A Highly Infectious Mycosis of Pet Animals
Mahendra Pal*and Raj Mahendra1
Consultant of Veterinary Public Health and Microbiology, 4 Aangan, Jagnath Ganesh Dairy
Road, Anand-388001, Gujarat, INDIA
1
Shashwat Clinic, Panchbatii, Bharauch-392001, Gujarat, INDIA
*Corresponding author: [email protected]
Rec. Date:
Jan 15, 2017 23:39
Accept Date:
Jan 27, 2017 18:15
Published Online:
January 29, 2017
DOI
10.5455/ijlr.20170129071049
Animals. International Journal of Livestock Research, 7(1), 1–7. doi:10.5455/ijlr.20170129071049
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How to cite: Pal, M., & Mahendra, R. (2017). Dermatophytosis - A Highly Infectious Mycosis of Pet
1
Abstract
Dermatophytosis is a highly infectious mycotic disease of great economic, and public health
consequences. It is estimated that 20 % of world population is affected with dermatophytosis. The disease
is cosmopolitan in distribution, and has been frequently reported in humans as well as in many species of
animals including cats and dogs. Dermatophytosis is an occupational mycozoonosis of pet owners, dog
handlers, kennel attendants, dog trainers, dog catchers, veterinarians, and persons working in animal
shelters. Among several species of dermatophytes, Microsporum canis is the principal cause of ringworm
in cats, and dogs; and is recognized as an emerging pathogen of global significance. Transmission of
infection can occur by direct contact with diseased animal and man, indirect contact with contaminated
fomites or contact with soil. The disease is more severe and common in kittens and puppies. Direct
microscopical demonstration of dermatophytes in skin /nail lesions by potassium hydroxide technique,
and its isolation in pure growth on Sabouraud medium/DTM still considered the mainstay of diagnosis. A
number of topical agents (miconazole, clotrimazole, terbinafine, luliconazole), and systemic drugs such
(griseofulvin, ketoconazole, fluconazole, itraconazole) have been tried for the management of disease.
The identification of asymptomatic carrier in kennels and catteries by culture of brushing, and use of
Wood’s lamp in screening of pet colonies where M. canis is the only concern, is recommended. The role
of T. bullosum, a newly emerged zoophilic dermatophyte in the etiology of canine and feline ringworm
should be investigated. It is emphasized that Narayan stain, which is cheap, easy to prepare and stable at
room temperature, should be widely employed in microbiology and public health laboratories for the
morphological studies of dermatophyes, which are implicated in the etiology of human and animal
ringworm.
Key words: Canine, Dermatophytes, Direct Microscopy, Feline, Microsporum Canis, Narayan Stain,
Ringworm, Zoonosis
International Journal of Livestock Research
eISSN : 2277-1964 NAAS Score -5.36
Vol 7 (1) Jan’17
Introduction
Fungi have emerged as a significant cause of morbidity and mortality in humans and animals throughout
the world (Pal, 2007). Recently, there has been an increase in the incidence of fungal infections in
developing countries. This may be due frequent and prolonged use of antibacterial antibiotics,
corticosteroids, immunosuppressive drugs, neoplastic agents, HIV/AIDS, leukemia, lymphoma,
neutropenia, tuberculosis, diabetes mellitus, organ transplantation besides environmental condition (Pal,
2007; Jain et al., 2014). Dermatophytosis (ringworm, tinea) is the most commonly encountered
superficial and highly contagious mycosis of humans and animals (Van Cutsem and Rochette, 1991; Pal
and Dave, 2005; Pal, 2007; Pal and Dave, 2013; Dave et al., 2014). Disease is reported from many
countries of world including India ( Ainsworth and Austwick,1973; Baxter and Rush-Munro, 1980; Pal,
1981; Wright,1989; Bond,2010; Pal and Dave,2013; Dave et al.,2014; Jain et al.,2014); and occurs in
sporadic as well as in epidemic form (Pal,1981; Pal and Thapa,1993; Pal and Lee,2000; Pal and Dave,
2005).Dermatophytosis is more prevalent in tropical and subtropical regions where the temperature and
relative humidity are high ( Pal, 2007; Jain et al., 2014). The public health implications of animal
dermatophytes are well established by many investigators (Pal and Lee, 2000; Pal and Dave, 2005; Dave
et al., 2014). In Africa, dermatophytosis is a common skin disease affecting more than 30 % of children in
primary schools (Pal, 2011).The global incidence of dermatophytosis is estimated 20 % (Pal, 2007).
David Gruby (1840) is credited to record for the first time the ringworm of scalp in children due to
Microsporum audouini (Pal, 2007). However, the first record of ringworm in dogs due to Microsporum
canis was established by Bodin and Almy in 1897 (Pal, 2007). In cats and dogs, M. canis is the most
common cause of dermatophytosis (Wright, 1989). Healthy cats and dogs may remain asymptomatic
carriers of M. canis , and hence pose a great risk to humans, particularly those who remain in contact with
pet animals (Pal,2007).It is pertinent to mention that about 30 % of dogs and cats in USA are infected
with M. canis, a frequent cause of tinea capitis in children (Pal,2011). It is reported that about 80 % of
human ringworm in rural areas, and 10 % in urban settings are of animal origin (Pal, 2011).The present
communication focuses on the growing significance of dermatophytic fungi, especially M. canis in the
etiology of canine and feline ringworm.
Etiology
Disease is caused by dermatophytes, which are keratin digesting, aerobic, non-motile, non-capsulated,
filamentous fungi. Dermatophytes represent 42 species classified in three genera namely,
glutaraldehyde (CFSPH, 2013). In cats, about 98 % of ringworm infection is caused by Microsporum
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and also susceptible to sodium hypochorite, idophors, formaldehyde, benzalkonium chloride, and
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Epidermophyton, Microsporum and Trichophyton (Pal, 2011). They are sensitive to dry, and moist heat,
International Journal of Livestock Research
eISSN : 2277-1964 NAAS Score -5.36
Vol 7 (1) Jan’17
canis. However, in dogs, M. canis is responsible for over 70 % of cases (Aiello and Mays, 1998).The
other dermatophytic fungi isolated from canine and feline include M. gypseum, M. persicolor, T. equinum,
T. erinacei, T. mentagrophytes, T. rubrum, T. tonsurans and T. verrucosum (Ainsworth and
Austwick,1973; Pal,1981; Pal et al.,1990; Yamada et al.,1991; Bernardo et al., 2005; Brilhante et
al.,2006; Sharma et al.,2009; CFSPH,2013).The spores of M. canis in infected building can remain viable
for one year (Menelaos ,2006).
Transmission
The source of infection is always exogenous. The cats and dogs can be infected with zoophilic (animal)
dermatophytes, geophilic dermatophytes (soil), and anthropophilic dermatophytes (man). The direct
contact with patient and indirect contact with contaminated fomites serve as means of transmission of
dermatophytes. The infection can also be acquired from the contaminated soil (Pal, 2007).
Clinical Symptoms
Cats
Many cats with dermatophytes show few or no lesions. The cats may develop a carrier state in the
absence of clinically appearing lesions, and can represent an insidious source of contamination to other
animals (Menelaos, 2006). The kittens are most frequently affected, and typical lesions which consist of
focal alopecia, scaling, and thin, greyish white crusts, are mostly observed around the ears, and face or
extremities (Aiello and Mays, 1998)). These lesions may or may not pruritic. The grooming nature of the
cats may eventually spread the infection to the entire body. The large, alopecic, and exudative lesions
occur in severe form of ringworm in debilitated cats. In some long haired cats, especially Persians, the
firm, subcutaneous nodules known as pseudomycetoma, are seen on the neck and back (CFSPH,
3013).True feline mycetoma due to M. canis, which is a rare clinical manifestation, is reported from
Japan by Kanbe and other (2009).Occasionally, the nails may be affected along with the skin and hairs
(CFSPH,2013).
Dogs
The ringworm infection is most commonly encountered in young dogs less than 1- year-old (Menelos,
2006). The lesions in puppies may show alopecia, scales, vesicles, pustules, and crust. Other forms of
dermatophytosis include kerion, and pseudomycetomas. In addition, onychomycosis may occur
uncommon in dogs, and is usually accompanied by immunodeficiency (Aiello and Mays, 1998).
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exposed to dermatophytes, may have developed immunity (Menelaos, 2006).The generalized ringworm is
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concurrently with ringworm infection (CFSPH, 2013). Older dogs are less susceptible, and if previously
International Journal of Livestock Research
eISSN : 2277-1964 NAAS Score -5.36
Vol 7 (1) Jan’17
Diagnosis
The clinical signs are not very characteristic to warrant the diagnosis of dermatophytosis. In
immunosuppressed patients, laboratory test include a complete blood count, biochemical profile, and
urine analysis. The examination of lesion or infected hair under Wood’s lamp is helpful to make a
tentative diagnosis of canine and feline ringworm caused by M. canis. This zoophilc dermatophyte
exhibits a bright greenish yellow fluorescence under UV light (Pal and Dave, 2013).The microscopic
examination of skin scrapings, broken hairs or nails in potassium hydroxide (KOH) solution reveal the
presence of thin , long , branched hyaline hyphae and arthrospores (Pal, 2007).The isolation of
dermatophytes is attempted in Sabouraud dextrose medium with chloramphenicol and actidione (Pal,
2007) and also on dermatophyte test medium (DTM) (Taplin et al.,1969).The later medium becomes red
due to rise in pH through metabolic activity of dermatophytes (Pal and Dave,2013). As some of the
dermatophytes grow slowly, the incubated media should be examined daily for up to four weeks before
discarding as negative. The detailed morphology of dermatophytes is studied in Narayan stain (Pal,
2004).This stain contains 0.5 ml of methylene blue (3 % aqueous solution),6.0 ml of dimethyl sulfoxide
(DMSO) and 4.0 ml of glycerin. The skin biopsy should be performed in nodular dermatitis or in the
event of negative cultural finding. The hyphae and arthrospores are better demonstrated by periodic acid
Schiff (PAS) technique (Pal, 2007).Very recently, molecular tools are also applied in the diagnosis of the
dermatophyte infections (Brilhante et al.,2006; Kanbe, 2008; Jensen and Arendrup, 2012).The differential
diagnosis includes bacterial folliculitis, demodicosis, malasseziosis, scabies, and seborrheic dermatitits
(Pal, 2011).
Treatment
Most infections in healthy animals heal spontaneously within one to a few months. The primary objective
of treatment in dermatophytosis of pet animals are to hasten the speed of recovery ,prevent the spread of
infection, and reduce the risk of transmission to humans and other animals (CFSPH, 2013). The treatment
for ringworm infection can be frustrating due to its relapse, and expensive because of high costs of
antifungal drugs. Both topical and systemic therapy is recommended in small animal clinical practice.
Local lesion may be treated with topical application of miconazole (2%), clorimazole (1%), terbinafine
(1%), and luliconazole (1%) cream. The drug is applied as a thin layer twice a day on the lesions for 15 to
21 days. In chronic, severe, generalized cases, and also in long haired cats, systemic therapy is indicated.
A number of drugs such as griseofulvin (25-100 mg/ kg body weight) in dog, and (25-50 mg /kg body
(5 mg/kg body weight) are given daily. The cats may develop bone marrow depression; especially the
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neutopenia at higher doses of griseofulvin. This drug is highly contraindicated in pregnancy. Moreover,
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weight) in cat in divided doses with fatty meal, ketoconazole (10 mg / kg body weight), and itraconazole
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International Journal of Livestock Research
eISSN : 2277-1964 NAAS Score -5.36
Vol 7 (1) Jan’17
gastrointestinal upset is a common sequela of griseofulvin administration (Aiello and Mays,
1998).Treatment for ringworm should be continued for 2 -4 weeks past clinical cure (Aiello and Mays,
1998). It is advised that mycological monitoring of therapy is imperative to see the efficacy and response
of drugs.
Prevention and Control
The complete eradication of dermatophytes from the environment of catteries, kennels, and animal
shelters seems impracticable. However, proper cleaning and disinfection of premises, decontamination of
fomites, isolation of sick animal, quarantine of newly purchased pet and its fungal culture for the presence
of dermatophyte, treatment of affected pets will certainly minimize the prevalence and incidence of
dermatophytosis in cats and dogs. As animal dermatophytes are highly communicable to human beings,
persons keeping the pets should be imparted health education about the source of infection, mode of
transmission and personal hygiene (Pal, 2007; Pal and Dave, 2013). It is emphasized to detect the
infection of dermatophytes in asymptomatic carrier animals by employing standard mycological
technique.
Conclusion
Dermatophytosis, a global, superficial, infectious mycotic disease of humans and animals, is caused by
many species of dermatophytes. The disease is reported from developed and under developing nations of
the world. In cats and dogs, M. canis is the most common cause of ringworm. Clinically affected and
asymptomatic pets are an important source of ringworm in humans particularly in children. About 30 %
of animal ringworm cases can lead to human involvement. Chronic or aggressive steroid therapy has been
associated with protected disease. The infection can be more persistent or widespread in young or sick
animals. Since zoophilic dermatophytes have public health implications, proper care must be observed
when dealing with the sick animals. It is advised that immonocompromised patients should not handle the
pet animals. As M. canis has emerged as a global pathogen, its role in various dermatological disorders of
humans and animals should be further investigated. More studies are needed to develop a potent, safe, and
low cost immunotherapeutic agent to protect canines and felines from ringworm, which is an important
fungal zoonosis of global significance.
Acknowledgements
We are highly indebted to Prof. Dr. R. K. Narayan for critically reviewing our manuscript. Thanks are
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also due to Anubha Priyabandhu for sending some of the relevant literature on the subject.
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