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Dermatophytosis 247

Dermatophytosis Bonus Material Client Education
Sheet
Online
VetBooks.ir Clinical Presentation Diseases and Disorders
BASIC INFORMATION
DISEASE FORMS/SUBTYPES • Arthrospores attach within 2 hours of contact
and start invading and germinating in skin
Definition • Subclinical infection: incubation period from in 6-8 hours.
A superficial fungal disease of the keratin of contact with spores to invasion of skin and • Infection requires spore exposure,
hair, skin, or claws hair is ≈7 days, and these early lesions are microtrauma, and moisture for successful
easily missed in dogs or cats. establishment. Active infection with shedding
Synonyms • Kerion: an uncommon, overly exuberant of spores can occur within 7 days, as docu-
Ringworm immunologic/inflammatory response leading mented by biopsy, Wood’s lamp examination,
to thickened plaquelike to smooth, nodular direct examination, and fungal culture.
Epidemiology growths or masses; more common with • Dermatophytosis is a self-curing disease
SPECIES, AGE, SEX Trichophyton infections in healthy animals, and most infections
Cats and dogs of either sex and any age • Mycetoma or pseudomycetoma: rare pyo- resolve without treatment in 28-100 days.
granulomatous draining nodules from deeper Recovery is associated with development of
GENETICS, BREED PREDISPOSITION extension of infection in an immuno- a strong cell-mediated immunity (CMI);
Persian, Himalayan, and Rex cats and Yorkshire compromised host; more common in Persian lack of development of CMI results in
and Jack Russell terriers are overrepresented. cats persistent infection until a treatment
intervention.
RISK FACTORS HISTORY, CHIEF COMPLAINT
• Seropositive feline immunodeficiency virus Skin lesions seen in newly acquired pet. Owner DIAGNOSIS
(FIV) or feline leukemia virus (FeLV) may also have skin lesions.
status in cats alone does not increase risk of Diagnostic Overview
disease. PHYSICAL EXAM FINDINGS Diagnosis is based on clinical signs and use of
• Hunting and working dogs are at increased • Focal to multifocal areas of hair loss, complementary tests (see below). No one test
risk for disease and kerion reactions. scaling, crusting, hyperpigmentation, with is considered the gold standard.
• Physiologic stress from concurrent illness, or without erythema and variable pruritus.
poor nutrition, endoparasitism or ectoparasit- Lesions tend to be asymmetrical and can Differential Diagnosis
ism, neoplasia, poor husbandry, overcrowding mimic pyotraumatic dermatitis (dogs) or • In dogs, rule out superficial staphylococcal
in conjunction with microtrauma to skin, eosinophilic lesions (cats). pyoderma and demodicosis.
and concurrent spore exposure are major • Early lesions are most commonly found in • In cats, rule out flea allergy and mite infesta-
risk factors for adult animals. thinly haired areas (face) and on extremities. tions. Other allergies should be considered
• Group housing in shelters, rescue agencies, • Uncommon: pustular lesions or lesions that along with other causes of generalized scaling
pet stores coupled with exposure and the resemble pemphigus and pruritus. Common disease in kittens but
risk of microtrauma to the skin increase uncommon in adult cats
prevalence. Etiology and Pathophysiology
• Causes: M. canis, Microsporum gypseum, and Initial Database
CONTAGION AND ZOONOSIS Trichophyton spp. M. canis is more commonly • Careful dermatologic examination in room
• Dermatophytosis is a low-level zoonotic involved. Feline infections with Trichophyton light, followed by Wood’s lamp examination.
disease; infection in people causes skin lesions are common in winter and/or in cats from This is a highly useful tool for identification
and is curable. farms. of lesions not visible in room light.
• Most common complication of Microsporum
canis infections in immunocompromised
people is possible prolonged treatment time.
• Disease is transmitted by direct contact
between an infected animal to another
susceptible animal or person.
• Infection from contaminated environments
is a commonly cited risk factor, but there
is only one documented case; mechanical
carriage of spores on the hair is a confounder
for environmental contamination.
• M. canis is not part of the normal fungal
flora and isolation indicates true infection or
mechanical carriage, but mechanical carriage
is not infection, and the term carriers should
not be used.
• Refer humans (clients or staff) to medical
doctors for consultation regarding treatment
of their lesions.
GEOGRAPHY AND SEASONALITY
Disease prevalence is higher in warmer tropical DERMATOPHYTOSIS Ambient white light examination of an affected cat shows periocular moist dermatitis
or subtropical geographic regions, particularly and erythema bilaterally, extending to the left lateral bridge of the nose. Under white light, lesions suggest
in locales with large stray animal populations. simple upper respiratory tract infection. (Copyright Alana Canupp.)

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