Dermatophilosis - Horse

Also known as: Cutaneous streptothrichosis — Rain Scald — Mud Fever

Also see General Dermatophilosis for more information.

Clinical Signs

Three clinical syndromes have been documented:

They occur usually due to a repeated wetting of the stratum corneum or skin trauma which makes the skin more vulnerable to parasitism by the causal agent Dermatophilus congolensis. It is more commonly seen in the winter. Typically hair becomes matted and focal lesions develop into crusts and thick scabs covered by layers of yellow-green pus. When scabs are removed the hair is taken with them and alopecia results.

Rain scald commonly affects the dorsum, shoulders and neck. It can however extend to lower portions of the body and abdomen. It typically begins as small rough raised bumps and can go un-noticed in long haired regions.

Mud fever looks similar to rain scald but affects the pastern and distal limbs. White legs and white skinned areas are most commonly affected.

Grease heel is a disease complex described in its own page. Dermatophilus is not always involved.


Bring affected animals into a dry environment and isolate. Scabs should be soaked and removed. Chlorhexidine and benzoyl peroxide are recommended as topical antibacterials.

Tack and any other equipment should be disinfected to avoid further infection. Systemic antibiotics should be administered if secondary infection is present. Owners should be educated about the condition and warned that the disease may reoccur in wet weather.

Dermatophilosis - Horse Learning Resources
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Equine dermatophilosis


Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial

4th year Veterinary Dermatology notes. Royal Veterinary college. October-November 2008. p60-64.

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