Winter and Spring is the time of year for mud fever. This is a skin infection caused by an organism called Dermatophilus congolensis which lives in the soil. In winter, the skin is softened by rain and mud. Continual wetting and drying causes the skin to chap and allows the bacteria to enter. Muddy conditions are not always necessary; wounds or grazes can also allow the bacteria to penetrate.
Mud fever is recognized by scabs, a crusty exudate, and matted hair. It is usually seen around the coronet, heels and pastern, although scabs may form anywhere. It is more common on white legs with pink skin. In severe cases it can cause the legs to swell up and the horse may become lame. It affects cattle, goats and sheep.
Treatment of mud fever must be vigorous and immediate. It is important to remove all scabs and exudate as these harbour the bacteria. Removing the scabs can be uncomfortable for a horse, so it helps to first soften the scabs with warm soapy water and then clean down to pink healthy skin using a dilute antiseptic solution such as iodine wash or Malaseb shampoo. In severe cases, poulticing may be required to soften the scabs. Afterwards ensure that the leg is thoroughly dried.
Once dried, an antibiotic cream such as Bioderm® should be applied twice daily. The scabs and crusts will reform rapidly therefore it will be necessary to repeat the antiseptic wash daily until the legs are completely healed.
If the leg becomes swollen or the horse becomes lame, then veterinary attention is needed. Severe cases may require a course of antibiotics and anti-inflammatories.
Allowing the legs to dry after exercise, followed by brushing off any mud appears to be the best management practice. If your horse acquires minor scabs on the legs, a close watch should be kept to ensure that they do not develop into mud fever. This condition is much easier to treat if it is recognized early!
David McDonnell BVSc Massey, MACVSc, DipBusStud