Summer Sores in Horses

Summer sores or habronemiasis can appear anywhere on the body that flies are able to rest and feed, especially around the eyes, face, prepuce and penis, or on any wound. Flies carry the larvae of Habronema worms onto these areas where they cause a severe inflammatory reaction, sometimes with a yellowish-white center.

The lesions can sometimes look similar to proud flesh. Irritation and biting or rubbing of the area is common. Often the inflammation will subside in winter and reappear the next summer. Summer sores are most common in very hot, wet areas, but in some years the condition is widespread wherever large numbers of horses congregate.

Ivermectin or moxidectin, both dewormers, are the best form of treatment and a response to treatment can be diagnostic. Surgical removal of the lesions is possible, combined with certain insecticides or dewormers that are applied to the skin or given orally. Fly control is necessary. Veterinary assistance is needed to diagnose and treat habronemiasis.