- Definition
- Pathophysiology
- Systems Affected
- Genetics
- Incidence/Prevalence
- Geographic Distribution
- Signalment
- Signs
- Causes
- Risk Factors
BASICS
- Superficial cutaneous fungal infections develop in the stratum corneum, hair, and hoof. They include dermatophytoses and yeast dermatoses
- Dermatophytoses are generally highly contagious dermatoses due to keratinophilic fungi of the Microsporum and Trichophyton genera
- Yeast—superficial fungal dermatoses. Most important yeasts are Malassezia and Candida albicans
- Dermatophytoses—2 zoophilic species identified specifically in horses: Trichophyton equinum and Microsporum equinum
- Transmission by contact with clinically infected or asymptomatic carrier horses, other animal species, insect bites, or fomites. Dermatophyte spores have a very long resistance in the environment (months to years)
- The spores remain quiescent until local conditions stimulate arthroconidia to germinate and invade the stratum corneum and hair follicles. Protease production digests keratin and initiates skin and hair damage
- Yeast—(Malassezia spp.) is a lipophilic yeast present on the skin of most horses. Proliferation may induce inflammation
Dermatophytoses—1 of the 10 most frequent skin conditions in horses. Higher incidence on training farms than breeding farms.
- Dermatophytes—any age. More frequent in young horses
- Yeast—no breed predilection. Malassezia (intermammary fossa) possibly more frequent in mares. Nonseasonal
- Clinical disease is usually evident within 1–6 weeks after exposure and clinical signs are highly variable
- Evolution influenced by host (age, immune status), fungus, and time. More inflammation is frequent with Trichophyton sp. Papules, tufted hairs, or urticaria-like lesions at early stage
- Annular alopecia (1–10 cm in diameter) and scaling with an erythematous margin. Become polycyclic by coalescence or grow centripetally. New hair growth may occur in the center of the lesion but active disease continues to occur at the periphery
- May have single or multiple lesions in a cluster or generalized
- Moderate erythema (visible on white horses)
- Crusts occasionally thick. Infrequently multiple papular forms (miliary). Subcutaneous forms (mycetomas) are rare in horses
- Pruritus usually minimal, except with Trichophyton bullosum
- Frequently starts on areas exposed to trauma or are in contact with saddles, bridles, and harness
- Most lesions are located on the face, neck, dorsolateral thorax, forelimbs, and girth
- More or less rapidly extensive
- Individual lesions spontaneously cure with regrowth of hair from the center (occasionally darker in color)
- Mane and tail generally spared
- Malassezia—intertrigo (axillae, groin, mammary gland, prepubital fossa); odor; greasiness and sticky brownish material
- Candida—acute inflammation, erythema, pustular, erosion, exudates (occasionally whitish) mainly periorificial, vulvovaginal, perineal, or intertriginous areas, occasionally pruritic (even painful if Candida). Nodular cutaneous candidiasis represented as firm, painful nodules covered by a normal hair coat has been reported
- Yeast—immunosuppressive diseases (viral infections, neoplasia) or immunosuppressive drug therapy may predispose to candidiasis
- Vulvovaginal candidiasis was reported in Thoroughbred mares following oral administration of a synthetic progestogen
- Defects in cornification and hypersensitivity
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS