Rain Rot

What is Dermatophilosis (rain scald)?

Dermatophilosis is caused by actinomycete bacteria, Dermatophilus congolensis. It usually occurs along the back of the horse during wet conditions in fall and winter. Transmission is from a carrier animal is by contact, insects, ticks and foreign objects (fomites). 

Clinical signs: The primary signs are hair loss and crusts which include the hair.

  • Hair loss at sites of tack on the back
  • Crusts with matted hair
  • Moist skin under the hair

Diagnosis: The diagnosis is made by microscopically  identifying the bacteria on impressions smears.

Treatment: Removing the affected hair and crusts followed by washing and tamed iodine or lime sulfur. Systemic penicillin or trimethoprim-sulfa are effective.

Prevention:  Keeping dirt and dander in the hair coat is normally effective. Cleaning tack and preventing contamination from affected horses should be practiced.