July 20, 2021 3 min read
Summer sores are anything but fun for both the horse afflicted and the owner. These oozing wounds, also known as habronemiasis, can take months to heal without the right management protocol and often make the horse unrideable.
Consider this: the horse in the stall next to yours develops a summer sore. You lucked out, right? At least it wasn’t your horse! Unfortunately, you’re not as lucky as you might think. While summer sores don’t spread directly from horse to horse, they are contagious. Understanding what they are, how they occur, and how they spread can help keep your horse safe.
So, how do they develop in the first place? Lucky for us, it involves our two favorite things as equestrians: parasites and flies. Summer sores are caused by the larvae of an equine parasite known as Habronema. Most of the time, the Habronema worm is able to live harmlessly in your horse’s stomach. Their eggs are passed through the horse’s digestive tract and into the manure. There, the larvae are ingested by maggots where they continue to develop. When the maggots are ready to fly, the larvae inside them are at the right age to find and infect your horse.
While most Habronema are ingested by the horse and continue their lifecycle in the mucosa of the stomach, problems begin when a larva is deposited in other moist areas such as the eyes, lips, genitals, and open wounds. Here it will start to burrow into the horse’s skin in search of a suitable living environment. After a short time, the larva will die and calcify. The ugly wounds that result are painful and itchy, causing self-mutilation as your horse bites and rubs at the area in an attempt to find relief. Habronemiasis will appear as an ulcer filled with light red granulation tissue, almost like proud flesh. It can contain pieces of dead tissue and may leak fluid.
Not all horses who are infected with Habronema display symptoms. It’s uncommon, but an unusually heavy load of Habronema worms can cause issues with ulcers and irritation of the stomach. Most of the time horses who are carrying Habronema in their digestive tract appear to be perfectly healthy. Despite their outward appearance, these infected horses are still shedding Habronema eggs into their manure. If houseflies are also present, these eggs can be ingested by the fly and transported to any horse on the farm.
If one horse on the farm develops a summer sore, chances are good that all horses on the farm are either infected or at high risk of becoming infected. Your horse may be one of the lucky ones that doesn’t develop a summer sore, but could still be carrying Habronema worms. Keep in mind that once Habronema is present on your farm, it’s only a matter of time until one of the horses develops a summer sore.
Equine Habronema are specific to the equidae population and can only survive in horses, donkeys, and zebras. There is no evidence that Habronema larvae can be transferred to humans via flies. Still, you should always follow proper hygiene protocols when managing equine Habronema. This can include wearing disposable gloves, using clean and sterile equipment, and washing your hands after you’re done. Not only will this prevent you from external bacteria, but it will also keep your horse’s open wound from developing a secondary infection.
Successful management of equine Habronemiasis requires deworming of every horse on the farm, whether they show signs of an active infection or not. This can be particularly difficult if a neighboring farm is not as diligent about deworming or fly prevention on their farm. But deworming alone is not enough to help a horse with a summer sore.
If you suspect your horse has a summer sore, follow the steps below:
Zarasyl is odorless, non-volatile, water miscible, chemically stable, non-irritating and non-toxic. Steroid and antibiotic-free, this FEI and race-day safe high-tech amorphous silica formula provides a sustained delivery of orthosilicic acid to the skin which is the bioavailable form of silicon associated with healthy connective tissue growth. Equestrians have noted “super success with a patient’s stubborn habronemiasis infection.”