With summer comes heat and humidity, and it is a time in many places where pesky flies are at their worst, which creates problems for many horse owners.
The increase in fly population can often lead to summer sores, medically known as Habronemiasis. Summer sores are lesions on the skin caused by the larvae of equine stomach worms Habronema.
These worms in the horse’s stomach produce eggs that pass through the digestive tract and are shed in the horse’s dung. Barn flies typically gather around manure and ultimately collect the parasite’s larvae on their extremities. Summer sores will outbreak when flies carrying the larvae deposit the eggs onto an open wound or the mucous membranes of the horse.
The larvae infect the open wound or mucous membranes, causing an inflammatory reaction including symptoms of inflammation, discharge, and the production of granulation tissue infected with larvae. One way to detect a summer sore is the visible granulation of tissue containing small yellow, rice-like larvae within the skin and a mucopurulent (mucus or pus-like) discharge associated with the wound.
Many different treatments have been tried, most with poor results, so prevention is the most effective way of controlling summer sore outbreaks.
The best way to protect horses is to implement an effective method for fly control, manure removal, proper wound care, and most importantly, an effective de-worming program to disrupt the parasite’s life cycle internally.
The popular dewormer, Ivermectin, has commonly been used to kill both adult worms in the stomach and the larval forms in the skin tissue. Corticosteroids are administered to reduce the inflammatory hypersensitivity reaction, and antimicrobials treat any secondary infections that may develop as the result of an open wound. If not treated properly, summer sores can last up to several months and possibly require a costly surgical procedure to remove the granulated tissue and larvae.
At the first sign of a summer sore, contact your veterinarian to discuss treatment and develop an effective fly management program.
Article courtesy Palm Beach Equine Clinic.