Re-Evaluate Your Deworming Protocols This Fall

by Dr. Kenton Morgan, senior veterinarian, Equine Technical Services, Zoetis

When did you last deworm your horse? What parasites did you deworm your horse against? If you’re not sure, it may be time to re-examine how you approach your equine deworming program.

Deworming every horse every couple of months was common practice for more than 40 years. However, the American Association of Equine Practitioners (AAEP) has revised their guidelines on parasite control. The guidelines now advocate for need-based deworming to avoid resistance in parasites by using a targeted treatment approach.

Many horses may need only two treatments per year in the spring and fall. However, horses at greater risk may need more frequent anthelmintic, or deworming, treatments. An individualized, risk-based deworming approach begins with a fecal egg count (FEC) test. Your veterinarian evaluates FEC tests before and after deworming to help determine a baseline for parasite levels and efficacy of the treatment.

Fall Parasites

Once your horse’s risk level is established, deworming treatments should be focused in the season of peak transmission, such as spring and fall when pasture refugia or parasite populations are at their highest. When considering a dewormer this fall, be sure to choose a complete dewormer that’s effective against encysted small strongyles (cyathostomins), the key parasite of concern in adult horses. And in the fall, we’re always concerned about tapeworms and bots.
Tapeworms can be difficult to diagnose even though they are common and widely distributed. A properly timed single annual tapeworm treatment is beneficial for most horses following the grazing season. In most areas, treatment should be given in the late fall or early winter when tapeworm transmission is low due to cold weather. Praziquantel, found in QUEST® PLUS Gel, is effective for treating tapeworms.1

Treat horses for bots once annually, during late fall or early winter as a cleanout. This will help decrease transmission the following season. Moxidectin, also an active ingredient in QUEST PLUS, is one of only a few equine dewormers effective against bots.1

Parasites can become resistant to deworming active ingredients when they are overexposed to them, leaving fewer treatment options. Small strongyles have been shown to have widespread resistance to fenbendazole.2 Moxidectin is the most effective treatment against small strongyles, but its use should be timed to control levels of egg shedding into the environment in the fall, when environmental conditions are conducive to egg development and larval survival.1

Individualized Deworming™

Because every horse is unique, the AAEP guidelines recommend working with your veterinarian to develop an Individualized Deworming™ plan tailored to your horse’s needs. Prior to purchasing a dewormer, ask your veterinarian to conduct an FEC test. Then evaluate your horse’s Individualized Deworming needs by answering a few questions on or via the EQStable™ app.

Do not use QUEST Gel or QUEST PLUS Gel in foals less than 6 months of age or in sick, debilitated and underweight horses. These products should not be used in other animal species, as severe adverse reactions, including fatalities in dogs, may result.
1 American Association of Equine Practitioners. AAEP Parasite Control Guidelines. Accessed August 30, 2016. 
2 Kaplan RM. Anthelmintic resistance in nematodes of horses. Vet Res. 2002;33:491-507. 
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