A disease of the skin which occurs as a result of continuous exposure to moisture, for example on the back and croup or horses kept outside in wet conditions or on the front of the cannon bones in horses which have their legs hosed down daily. The symptoms usually start as tufts of hair which are easily pulled out and progress to scabs and pustules over a larger area. The disease is caused by a bacterium called  Dermatophilus congolensis, which is frequently present on the skin of healthy horses and is easily transmittable from horse to horse as well as from horse to humans. To invade the skin, the bacterium requires small wounds or moisture softened skin.