Prevention is the best way to protect your horse from summer sores. Thankfully, summer sore prevention is tied to basic horse husbandry, including deworming, fly control, and wound care:
Control of stomach worms is the best way to help prevent summer sores. Adult stomach worms thrive in your horse's stomach and release their larvae into the digestive tract, where they are passed in your horse's manure and ingested by fly larvae. The fly larvae matures into an adult and the adult fly then deposits the stomach worm larvae onto your horse's wounds. To help break this cycle, use a strict deworming schedule.
Since flies serve as the intermediate host of stomach worm larvae, effective fly control is also essential. In addition, even if your horse is on a strict deworming schedule, horses in nearby pastures or on the same trails might not be and the stomach worm larvae they pass could be easily carried to your pasture or barn. To combat flies, set perimeter traps and use topical sprays. Spot-ons or suitable insect-repellent salves can add insect protection to your horse's more sensitive areas, including open wounds. Furthermore, fly masks and sheets can also help protect your horse's eyes, ears, mouth, and other moist body areas. Insect repellent supplements may also help kill fly larvae in your horse's manure.
Wounds, cuts, and abrasions are vital entry points for stomach worm larvae. Therefore, wound-free horses may have less chance of developing summer sores. Of course, horses often get wounded. However, immediately cleaning and treating any skin abrasions, cuts, or wounds helps speed healing. Similarly, a clean horse may have less chance of infection.