Mud fever can range from a mild skin irritation to very painful infected sores. It can cause swelling and lameness. It affects the lower legs, commonly the back of the pastern but can move up the leg. It starts off as matted hair with dry crusts, caused by the inflamed skin weeping.
It is caused by the Bacterium Dermatophilus congolensis present in soil. This bacterium cannot invade healthy skin but in winter, rain and mud soften the skin. If skin becomes chapped through repeated wetting and drying the bacteria can enter. Anything which breaks the skin such as a small cut or wound can allow the bacteria to invade. For this reason muddy conditions are not always necessary for mud fever to occur. It is largely a management issue although some horses are more prone to it particularly those with white skin. Hairy feathered horses are less prone due to the protection the feathers offer.
For further information on treatment, and prevention tip can be found here: