Many horse owners and veterinarians have reported a bad fly season this year and, for those residing in Southern states, there’s no end in sight. Flies are aggravating and distressing and bring along an inherent risk for summer sores.

“Summer sores are the product of a stomach worm, or Habronema (muscae) infection,” explained Nathan Voris, DVM, senior equine technical Services veterinarian for Zoetis. “As part of the Habronema life cycle, infective larvae are shed in horse feces and later picked up by houseflies. Infected flies deposit Habronema larva in open wounds, or into tissues around the horse’s mouth, lips, eyes, groin area damaged during feeding activities. The infection causes a significant inflammatory reaction, or summer sore. If Habronema and houseflies are both present, summer sores can be a problem for any horse.”

Persistent summer sores are extremely bothersome and slow to heal and, in many cases, remove the horse from training or showing. It’s a situation all too familiar to Carolyn Hornbeck of Raeford, N.C., and her 10-year-old American Quarter Horse gelding.

“He was a healthy horse that I’ve had for several years,” Hornbeck said. “It started out as a small sore on his ankle and, in no time at all, grew into a large wound comparable to the size of a giant filet (of steak) that would not heal. After a costly surgical procedure and eight months of (treatment), it scarred down to the size of a quarter and he was able to go back to riding