Small Animal Dermatology, 3rd edition

298 DISEASES/DISORDERS

disease; an underlying disease is identified in fewer than 50% of adult-onset gen-

eralized demodicosis cases.

 Treatment with immune-modulating medications, including oclacitinib and corticos-

teroids, is associated with increased incidence.

Cats

 D. cati: often associated with metabolic diseases (e.g., FIV, systemic lupus erythemato-

sus, diabetes mellitus).

 Both systemic and topical immunosuppressive therapy may trigger demodicosis.

 D. gatoi:rarely a marker for metabolic disease; individual reports indicate that it may

be transferable from cat to cat within the same household.

CLINICAL FEATURES

 Alopecia, scaling, follicular casts (keratosebaceous material adhered to the hair shaft),

comedones, crust, erythema, hyperpigmentation, lichenification.

 Secondary bacterial folliculitis and furunculosis often noted in chronic canine demod-

icosis; produces concurrent lethargy, fever, lymphadenopathy, and pain.

 Demodex injaiandD. gatoimay be associated with pruritus.

 Ceruminous otitis externa has been associated withDemodexmites in both dogs and

cats.

Dogs

 Localized:
Fewer than 4–6, often well-demarcated, small (less than 2.5 cm) lesions
Usually mild; consists of patches of erythema and light scale
Juvenile form often resolves without treatment
Most common site is the face, especially around the perioral and periocular areas,

as well as the front legs (Figure 19.6).

 Generalized:
Can be widespread from the onset, with multiple poorly circumscribed patches

of intense erythema, alopecia, papules, comedones, and scale (Figure 19.7)

As hair follicles become distended with large numbers of mites, secondary bacte-

rial infections are common, often with resultant rupturing of the follicle (furun-

culosis) (Figure 19.8)

With progression, the skin can become severely inflamed, exudative, and gran-

ulomatous (Figure 19.9)

Pododemodicosis: symptoms may be limited to the distal extremities; lesions

associated with deep secondary bacterial infection; Old English sheepdogs

reported at increased risk (Figure 19.10)

Demodex injai: most often causes an alopecic and oily patch on the dorsal midline

(Figure 19.11).