|First Posted: May 23, 2010|
Jun 19, 2012
Summer Sores, Jack sores, Bursatti, Habroniasis and Draschia megastoma in Horsesby Debora Johnson
Flies, flies, flies! Summer has arrived and so have those nasty flies. So, what are summer sores and what causes them? Yes, it is the common house fly and stable flies that are the intermediate hosts for the parasites that cause summer sores. Summer sores or habroniasis/Merck Vet Manual is a condition that affects horses. A parasitic larvae known as nematodes is the cause of summer sores.
"...Parasites that use flies as intermediary transportation to their horse hosts include the skin-aggravating Habronema and Onchocerca - Scroll down page to Neck Threadworms and the eye-invading Thelazia species (added: A genus of spiruroid nematodes that inhabit the lacrimal ducts and surface of the eyes of various domestic and wild animals but rarely of humans). Habronema hitchhike on biting stable flies and houseflies to gain entry through wounds or while flies are imbibing fluids from the horse's lips and nostrils. The larvae that mature in the horse's stomach after being swallowed aren't particularly troublesome, but those infecting wounds inhibit healing and encourage excessive tissue growth in the open wound. This reaction may in part be allergic, for the lesions tend to recur on those infected parts of the body every summer, hence their common name of 'summer sore.'
Midges pass along the thread-like filarial worms called Onchocercae. Though most horses tolerate these skin invaders without incident, some sensitive hosts develop skin eruptions on the head, neck, belly and chest, which, in turn, invite further fly attacks. Though the lesions heal rapidly, they frequently recur; dry, scaly skin shedding dandruff-like particles, particularly along the mane and withers, belly and chest, is the most common sign of Onchocercae infection and is easily confused with Culicoides itch. Eye worm probably afflicts a third of the world's horses, yet it does surprisingly little damage. House-and face flies act as vectors for this parasite, which normally remains in the inner corner of the eye but can sometimes be seen crawling over the eyeball itself. The parasite causes tearing, and the discharge may attract even more flies and subsequent eye infections...." Insect-borne Equine Diseases
Flies ingest the immature larvae and act as hosts for these parasites. The flies deposit these larvae on the horse's muzzle, skin, etc., while biting the horse. The horse eats the larvae and the adult nematode lives in the stomach of the horse, produces more larvae, the passes the larvae out in manure. Maggots (immature flies) feed on the manure thus ingesting the larvae, and the cycle repeats.
Any horse can get summer sores. None are immune, however, some are more predisposed than others. It is also important to know that the stomach worms (Habroniasis) can be passed along to other horses by the life cycle of the worm. As the cycle of the parasite recycles the flies can carry the larvae and vector it to other horses as the fly bites and draws blood, passing on the larvae. Therefore, it is really important to control this parasite and do your best to eradicate it.For More Information: