Summer sores are the common term for a skin condition caused by the larvae of Habronema and Draschia worms. As these larvae attempt to complete the next phase of their lifecycle, they may cause inflammatory reactions on your horse’s body.
Interestingly, these species of worms don’t migrate inside the horse, but complete their lifecycle in your horse’s stomach. While horses with only a small infestation may not show any clinical signs, a heavy infestation can be deadly – potentially leading to perforation and rupture of the stomach.
These worms begin their lifecycle when eggs are excreted in your horse’s manure. The eggs become larvae, and are often carried by house and stable flies to your horse’s mouth. Once they land on the lips, they are swallowed and grow into adult worms inside the stomach.
How Summer Sores Occur
However, Summer sores occur when the larvae land on other areas of your horse’s body and cannot enter the stomach. Their favoured environment are moist areas of the body, such as the eyes, ears and lips, but they can also occur elsewhere.
- Summer sores may occur when larvae are deposited on compromised skin or mucous membranes, such as the site of an injury or irritation.
- Parasites, like ticks, flies and midges, can also lead to persistent scratching and self-damage, leaving the skin susceptible to Habronema and Draschia
As the larvae cannot enter your horse’s system, they cause a severe local inflammatory reaction that results in swelling, ulceration, redness and itching. These rapidly-growing lesions are summer sores and often require veterinary care.