BASICS
Dermatophilosis is a common bacterial exudative crusting dermatitis of horses that may affect multiple horses in a barn but not necessarily all of them. It typically occurs during periods of heavy rain. Tightly adherent crusts most commonly affect the dorsum of the trunk, especially the saddle region or the dorsal surface of both hind cannon bones. It is a cause of pastern dermatitis (grease heal, scratches). This infection is easily resolved with topical and/or systemic antimicrobial therapy.
No age, breed, or sex predilection has been recognized. Horses that are debilitated may develop a chronic infection. If a horse is kept in a wet stall or pen, chronic pastern dermatitis may ensue.
- Clinical lesions vary with the stage of disease. Initially, follicular and nonfollicular papules and pustules form tightly adherent crusts
- Crusts may cluster to form large coalescing crusted plaques associated with a thick yellow to light green suppurative exudate. Removal of crusts results in the distal hair ends protruding through the crust, giving a “paint brush” appearance. Moist erosive erythematosus alopecic lesions are present when the crust is removed
- Alopecia is variable. If lesions are palpated pain may be elicited
- Pastern or fetlock involvement may cause lameness and localized swelling
- Lymphadenopathy may occur
- Dermatophilosis is caused by a Gram-positive, non-acid-fast facultative anaerobic actinomycete—Dermatophilus congolensis
- Skin damage and moisture seem to be the 2 most important factors required for an infection to occur. Skin damage allows colonization while moisture is important to promote growth of the organism
- Biting flies and ticks may spread the disease as well as fomites. Crusts, whether on the horse or in the environment, are infectious
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS