Prevention is the key to reducing your horse's risk of developing summer sores, and now is the time to begin preparations for the warmer, and fly-filled, months ahead.
 
Summer sores are caused by the larvae of two different types of stomach worms, known as Spurids. When the Habronema muscae and the Draschia megastoma larvae are deposited on skin abrasions or moist body parts such as eyes, nostrils, genitals, or ears, they can cause the skin lesions referred to as summer sores. But if they're larvae, how do they get onto the horse? They hitch a ride inside common flies.
 
Fly maggots in manure ingest the stomach worm larvae, and the larvae remain inside the flies until they mature; the larvae are then expelled when the fly is on your horse.
 

Summer sores can cause intense itching, leading your horse to bite or chew at the sore; this not only can cause secondary infections, it also delays the healing process and reinfects your horse with stomach worm larvae. Stomach worms have been known to cause ulcers in the stomach; plus, once horses have had summer sores, they can recur year after year.
 
Clearing up summer sores takes time and work, so it's better for everyone if you take steps now to control flies. Using fly predators and fly spray will help on your own property; banding together with neighbors to develop a community fly reduction program will help reduce the chances of infection in your region. Don't forget fly masks and sheets, and spot-control ointments or salves for fly control around wounds.
 
Once your horse has summer sores, while it's tempting to try and clear them up yourself, it can be cheaper in the long run to have your veterinarian pay a visit. A multi-faceted approach with antibiotics and anti-itch medications, plus appropriate Ivermectin-based dewormer, could be called for to interrupt the summer sore cycle.