This is a common bacterial skin infection that causes very distinctive "paintbrush crusts" to form on the skin. It is most commonly seen on the topline and lower limbs. The bacterial infection and inflammation causes the skin to ooze serum that sticks the hairs together in the classic way. These peel off together in a shape akin to a broad paintbrush stroke, leaving pink skin underneath.

This condition is more common in situations where the skin stays moist for extended periods of time. It is easily transmitted horse to horse via tack and grooming equipment, human handlers and insects.

The organism can live in removed hair crusts for a very long time so disposal of these is advised. The condition is not typically itchy (pruritic) but severely affected horses may be in discomfort from it, and removal of crusts may be painful. It is seen commonly in horses that are debilitated and immune suppressed from other causes.