Summer has arrived! With the humid weather, pesky flies are at their worst this time of year, which creates common problems for many horse owners. The increase in fly population can often lead to summer sores, medically known as Habronemiasis.
Summer sores on a horse's face. Photos courtesy of Palm Beach Equine Clinic
Summer sores are lesions on the skin caused by the larvae of equine stomach worms Habronema. These worms in the horse’s stomach produce eggs that pass through the digestive tract and are shed in the horse’s feces. Barn flies typically gather around manure and ultimately collect the parasite’s larvae on their extremities. Summer sores will occur when flies carrying the larvae deposit the eggs onto an open wound or the mucous membranes of a horse. The larvae infect the open wound or mucous membranes, causing an inflammatory reaction including symptoms of inflammation, discharge, and the production of granulation tissue infected with larvae.
One way to detect a summer sore is the visible granulation of tissue containing small yellow, rice-like larvae within the skin and a mucopurulent (mucus or pus-like) discharge associated with the wound. Prevention is the most effective way of controlling summer sore outbreaks and the best way to protect horses is to implement effective methods for:
- fly control
- manure removal
- proper wound care
- an effective de-worming program
A diligent de-worming program is the most important element of prevention because effective de-wormer disrupts the parasite’s life cycle internally. The key is to kill both adult worms in the stomach and the larvae that form in the skin tissue.
For treatment of summer sores themselves, corticosteroids are administered to reduce the inflammatory hypersensitivity reaction, and antimicrobials treat any secondary infections that may develop as the result of an open wound. If not treated properly, summer sores can last up to several months and possibly require a costly surgical procedure to remove the granulated tissue and larvae. At the first sign of a summer sore, contact your veterinarian at Palm Beach Equine Clinic at 561-793-1599 to discuss treatment and develop an effective fly-management program for your barn.