Rotational deworming–dosing horses with different classes of dewormers in rotation–is often recommended for controlling equine internal parasites. The theory is that by using all of the available effective deworming drug classes, we combine their benefits into a maximally effective program. However, some researchers say rotation isn’t a good idea because it contributes to parasite resistance and will reduce the effectiveness of available deworming drugs.

At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., two different viewpoints on rotational deworming were presented. We’ve included both here so you can see the evidence for both sides and make your own choices.

Presentation 1: Evaluation of Anthelmintic Rotational Regimens on a Previously Documented Fenbendazole-Resistant Farm

Wade Nichols, PhD, a senior technical services specialist at Intervet/Schering-Plough Animal Health, presented the results of a multiyear Texas Tech University study evaluating the efficacy of various parasite control strategies in a closed herd with documented resistance to fenbendazole