Mud fever is a skin condition that is not necessarily caused by mud but by a bacteria living in the mud called Dermatophilus congolensis. But it should be made clear that the bacterium isn't always found in muddy or wet areas. Although not as common, the bacteria that causes mud fever has been found in dry conditions like in Australia where the infection is commonly known as greasy heel or rain scald. The bacterium thrives in wet environments and enters the skin of the horse through cuts and abrasions.
Mud fever is sometimes referred to as grease heel and usually affects the lower part of the legs but can also travel up the legs to lower portions of the body. If the infection is in the pastern area, the horse may appear lame due to the inflamed skin and pain. The infection will start as a raw patchy area which will become pussy. This pus then hardens and forms a scab. Interestingly enough, mud fever is more common in horses with white hair which is believed to be due to the lack of pigmentation in the skin. Once this bacterium takes up home on the horse, it can survive for months because the scabs protect the bacteria from drying out.
For mild cases of mud fever, the treatment isn't complicated but it will take vigilance and time to get rid the horse of the bacteria. The bacteria must lose what is keeping it alive-moisture. The scabs will need to be removed and kept removed thus allowing the bacteria to dry up.
Clip away the hairs from any affected area. All of the scabs need to be removed which unfortunately is done by picking them off. A thorough washing in a high-quality antiseptic shampoo every few days will help keep the skin clean however, the skin will need to be fully dried after washing. Keep the scabs removed, this is the one case where having a raw sore is better than having scabs since the scabs protect the bacteria from drying out. One scab can harbor thousands of living bacteria so removing all of them is important. After removing the scabs, an antibiotic ointment should be applied to the affected sore at least twice a day. Do not apply bandages as this can allow dampness, the goal is to get the areas to dry out.
Checking a horse regularly for any cuts and abrasions should be a routine step in horse care. Keep any wounds clean and apply a wound ointment such as "cut heal" to the cuts. Keep areas that the horse has access to clean. Do not allow a horse to stay in standing water or muddy areas. Do not use brushes from infected horses on uninfected horses and any brushes used on horses with mud fever should be thoroughly sanitized before reuse. For infections that seem to be not healing after steady treatment or for severe cases, contact a veterinarian.