Deworming Dilemma

An owner seeks advice about deworming her horse that lives alone, travels to a public barn for exercise, and had a fecal sample that did not reveal any parasite eggs.
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Deworming Dilemma
If a horse is in good health and a fecal sample does not reveal any parasite eggs, there is simply no incentive to treat. | Photo: iStock
Q: I need advice about deworming our horse. He lives alone in a two-acre pasture, but he is hauled to a public barn for exercising. Our vet has advised us to cut back on the every-other-month deworming schedule after a manure sample showed he had no worms. How often should we deworm? Would you please recommend which medication we should use?

—Marty Ward, Medford, Ore.

A: Thank you for asking this highly relevant question. I fully agree with your veterinarian. To deworm a horse every other month is a serious overtreatment. In the best case it is not needed and is a waste of medicine and money and, at worst, such treatment regimens inevitably lead to resistant parasites.

You do not mention your horse’s age, but I assume he is an adult. Adult horses most often require only one or two treatments a year, and many may not need any treatments at all. If he is in good health and a fecal sample does not reveal any parasite eggs, there is simply no incentive to treat

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Written by:

Martin Krarup Nielsen, DVM, PhD, Dipl. ACVM, is an associate professor of parasitology and the Schlaikjer professor in equine infectious disease at the University of Kentucky’s Maxwell H. Gluck Equine Research Center, in Lexington. His research focus includes parasite diagnostic measures and drug resistance. Known as a foremost expert in the field of equine parasites, Nielsen chaired the American Association of Equine Practitioners’ (AAEP) parasite control task force, which produced the “AAEP Parasite Control Guidelines.”

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