The worm population on your farm includes the worms in each of the horses and also in manure and on the pasture. | Photo: iStock

How can you reduce internal parasite infection and manage anthelmintic resistance on your farm?

Do you know which of your horses has parasites? Chances are they all do, to one extent or another. What’s more important is knowing which horses have the highest fecal egg counts and which anthelmintic (deworming) treatments are effective on your farm. These are the first steps in developing a strategic horse parasite control plan for your farm.

When adopting such a management strategy, the primary goal is to prevent horses from amassing extremely high worm burdens, which, although uncommon, can cause signs of colic, diarrhea, and weight loss. Two secondary goals help achieve this:

1. Reducing the worm burden on pastures (which reduces horses’ rate of infection and reinfection); and
2. Maintaining the long-term ­efficacy of available dewormers.

​Equine parasitologist Martin Nielsen, DVM, PhD, Dipl. ACVM, an associate professor and the Schlaikjer professor of equine infectious disease at the University of Kentucky’s Gluck Equine Research Center, in Lexington, says that in managing your horses’ own parasite population, you are managing that of the entire