Question of the Day

Dermatophilosis is a crusting dermatitis caused by the filamentous bacteria Dermatophilus congolensis, seen in all ruminants and horses. Also called “lumpy wool” or “rain scald/rot.” 

Infection is seen most often in younger or systemically ill/immunocompromised animals. Many are housed in areas with poor hygiene or without shelter. Excessive moisture, rainy conditions, skin damage, and concurrent illness that results in immunosuppression are predisposing factors. 

Loss of the protective sebaceous film layer seen on healthy skin is thought to be an important factor in the pathogenesis. Carrier animals and fomites such as grooming tools are also important as this can be contagious in at-risk animals. 

Thick crusts, which usually contain the organism, look like the end of a paint brush when removed from the animal and are a typical finding. On cytology (impression smear of a crust) the “railroad track” appearance of the gram-positive cocci is classic for dermatophilosis. 

The infection self-resolves after a few weeks in most animals without treatment. Can use topical and systemic antimicrobials in persistent cases.

Images courtesy of Dr. Patrick Hensel.