Call it rain scald, scratches, mud fever, or mud rash, dermatophilosis is a skin infection caused by the bacteria Dematophilus congolensis. The bacteria thrives in muddy, wet conditions, and enters through damaged skin or sores. In some cases, it may be mistaken for ringworm.
Palomino horses in pasture with environmental conditions condusive to dermatophilosis
Dermatophilosis is most prevalent in horses that are very young, very old, immunosuppressed or chronically exposed to moisture.
The infestations of bacteria create pus that sticks to the ends of tufts of hair. When the tufts of hair fall out, scabs form over collections of pus in the tissues.
When the disease is on the legs, it is often referred to as mud fever or rash. When the bacterial infestations are on the body, it is known as rain scald. If not treated promptly, secondary infections by Streptococci and Staphylococci may occur.
- Pus-filled sores and scabs
- Tufts of matted hair with pus on the tips
- Tender, painful areas
Dermatophilus congolensis becomes active in wet, soggy pastures, and during the rainy season of the year.
As temperatures rise and rainfall and other wet conditions develop in many areas, horses that are pastured or maintained in areas where the ground is often wet may develop the condition Dermatophilosis also known by several descriptive names.
While many horse owners think the bacteria that causes Dermatophilosis lives in the soil, it is actually carried on a horse's skin. Some horses become immune to the bacteria, but others are affected year after year, usually during a warm, wet season, although the condition can occur during wet winter weather.
Two conditions must be present for Dematophilosis to develop:
- Wet weather
- A break in the skin of the horse
Dermatophilus is most prevalent in horses that are very young, very old, immunosuppressed or chronically exposed to moisture. Biting insects or infected tack, brushes or blankets may spread the infection from horse to horse.
The bacteria can live on damp fence posts, stall doors and other places where horses often rub themselves. If a horse is a carrier of the dermatophilosis bacteria, another horse rubbing itself in the same spot may become infected if there is a break in the horse's skin.
Once the bacteria is under the skin of the horse, it produces thread-like tentacles that spread in many directions. The bacteria likes anaerobic conditions meaning that it thrives in an environment where the oxygen content is low or absent
Prevention
Keeping horses in dry areas with dry bedding and stalls is the best prevention.
Treatment
Horses should be stabled in dry conditions. The infection is responsive to a course of antibiotics, and topical agents work well. Infected areas should be clipped out, and scabs softened and lifted off. If scabs are not easily removed, soak or shampoo until they soften and can be gently removed with a soft brush.
If possible, burn the tufts of hair and scabs to prevent further infection of other animals. A veterinarian-recommended antibacterial wash in warm water should be used to cleanse the areas, after which they should be patted dry with absorbent paper towels. Continue the treatments until the skin heals.
If staph infection is suspected, have the veterinarian do a culture since further treatment may be necessary.