Common Dewormers: Still Effective Against Small Strongyles?

Study results revealed that three commercially available dewormers showed poor efficacy on the majority of farms tested.
Share
Favorite
Close

No account yet? Register

ADVERTISEMENT

Common Dewormers: Still Effective Against Small Strongyles?
Study results revealed that three commercially available dewormers showed poor efficacy on the majority of farms tested. | Photo: Kristen Janicki/The Horse
We know that anthelmintic (or dewormer) resistance in equine internal parasites—meaning the drugs we use are becoming ineffective against the parasites they’re designed to control—is changing the way researchers and veterinarians recommend that we deworm our horses. “But what are the odds that I’ll have this problem on my little farm,” you wonder. According to recent study results, the odds are pretty good: They suggest that some commercially available dewormers—fenbendazole, oxibendazole, and pyrantel pamoate—showed poor efficacy on the majority of farms sampled during the project.

In the study, nearly 1,000 horses from 67 farms in the mid-Atlantic region of the United States received one of four different deworming products. At the same time a fecal sample was collected for analysis for parasite eggs. The horses with strongyle fecal egg counts totaling over 200 eggs per gram were retreated with fenbendazole, oxibendazole, or pyrantel pamoate. Of those horses, only 6%, 21% and 43%, respectively, showed fecal egg count reductions greater than 90%.

“On the majority of farms sampled, these three products performed poorly,” said study author Meagan A. Smith, DVM, Dipl. ABVP, staff veterinarian for the University of Pennsylvania’s School of Veterinary Medicine’s Field Service.

Deworming infographic feature image
RELATED CONTENT | Infographic: Deworming Adult Horses

Currently, ivermectin and moxidectin—two macrocyclic lactone medications—still offer good control against small strongyles. “Their continued efficacy is significant because so far they are the only available dewormers for horses that still have consistently good activity against strongyles,” she said

Create a free account with TheHorse.com to view this content.

TheHorse.com is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into TheHorse.com.

Start your free account today!

Already have an account?
and continue reading.

Share

Written by:

Katie Navarra has worked as a freelance writer since 2001. A lifelong horse lover, she owns and enjoys competing a dun Quarter Horse mare.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

Which skin issue do you battle most frequently with your horse?
259 votes · 259 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!