Bots and Beyond: Summer Equine Parasite Risks

Bots and Beyond: Summer Equine Parasite Risks

Photo: Erica Larson, News Editor

All horses are at risk from summer-loving parasites. Whatever your climate and wherever your horse resides--from stalls to pastures or dry lots--these parasites thrive during summer months. Here's how some of these parasites can infect your horse, what damage they do, and how to best control them.

Bots (Gasterophilus spp.): Female bot flies lay eggs on the horse's hair. The eggs are stimulated to emerge by the horse's licking or biting and, within five days of being deposited by the female, develop into larvae. Subsequently, the larvae make their way into the horse's mouth. Once inside the horse's mouth they bury themselves in the tongue, gums, or lining of the mouth. During this stage, the horse could experience severe irritation, pus pocket development and loosened teeth; loss of appetite can also develop at this stage.

After about a month in the mouth, the larvae molt to the second stage and move into the stomach. The second and later third stage larvae typically attach to the lining of the stomach and the intestinal tract. They cause irritation and can block the opening to the small intestine as well as interfere with digestion; chronic gastritis, ulcers, colic and other conditions can result.

Dewormers for Bots: ivermectin; moxidectin has limited control

Stomach worms (Habronema spp. and Draschia spp.): These parasites are responsible for producing "summer sores" (non-healing wounds) and internal problems. Infection occurs when flies deposit infected larvae on the horse's lips, nostrils, or open sores. When eggs are deposited in wounds, "summer sores" can occur. In large numbers, habronema can produce severe gastritis, and tumor-like enlargements can develop in the stomach wall. If they rupture, peritonitis (inflammation of the membrane lining the abdomen) usually ensues.

Dewormers for Stomach worms: ivermectin; moxidectin controls adult stage Habronema

Filarial parasites (Onchocerca spp.): Adult filarial parasites reside quietly in the nuchal ligament, which spans from the withers to the poll. When larvae called microfilaria develop, however, they migrate through the bloodstream and to the skin. Signs of filarial parasite infection include small lumps on the chest, withers, neck, face, and belly; itching and rubbing, resulting in loss of hair and scaly skin; development of scabby, weeping sores; moon blindness; and fistulous withers.

Dewormers for Threadworms: ivermectin

Don't let these parasites interfere with your horse's health this summer. Many products, including Durvet's ivermectin paste, are very effective against each of these parasites. Talk to your veterinarian about developing an individualized deworming program.

About the Author

Durvet, Inc.

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