Dealing with Summer Sores
Jessica Van Scyoc, DVM
One of the most frustrating summer problems a horse owner can face is cutaneous habronemiasis, or “Summer Sores.” Summer sores are a common problem, especially prevalent in California and Florida. Clinical signs of the disease include circular lesions made up of granulation tissue containing small yellow nodules. They can sometimes start from a previous scratch or injury. The wounds are typically around the eye, genitalia, lips, or lower limbs. They usually show up in the spring, and can last throughout the fall. Once a summer sore pops up, it will unfortunately tend to recur every year.
The parasites Habronema and Draschia are the cause of summer sores. The adult parasites live in the stomach of the horse, and pass larvae out through the manure. Stable flies that land in manure pick up the larvae, and either deposit it on the lips of the horse (to be swallowed into the stomach again), or on the eye/penis/lips/legs to form a sore. The sore is the body’s reaction to the foreign larvae.
Correct diagnosis is critical. Usually, a biopsy is necessary to distinguish a summer sore from proud flesh, squamous cell carcinoma, Pythium, or a sarcoid. Once confirmed, treatment centers around two factors.
1- Fly control: Since flies transport the larvae, fly control is essential to decrease the chance of infection. Fly spray with a minimum of 2% permethrin should be applied in late afternoon. Automatic insect repellent systems work well to control flies in the barn.
2- Wound care: Topical treatment with ointment (usually a mixture of anti-inflammatory and deworming agents) is helpful. The veterinarian may elect to inject steroids directly into the wound to decrease immune response. If possible, keeping a clean bandage on the wound helps to keep it covered with ointment as well as prevent fly irritation. In severe cases, oral steroids and/or surgery may be necessary.
If you think your horse may have a summer sore, please contact the office for an appointment at (321) 639-4242.