Implementing a Deworming Program Based on Fecal Egg Counts (AAEP 2010)

Most horse owners are diligent about deworming their horses on a regular schedule. But there might be a more efficient deworming program that both horses and their owners can benefit from. According to Claudia K. True, DVM, a practitioner with Woodside Equine Clinic in Ashland, Va., basing a deworming program on fecal egg counts allows each horse an individualized deworming schedule and reduces the possibility of developing anthelmintic resistant parasites.

During a presentation at the 2010 American Association of Equine Practitioners convention, held Dec. 4-8 in Baltimore, Md., True outlined an approach to developing a deworming program based on the horse's individual needs by performing routine fecal egg counts.

"The use of routine fecal egg counts allows veterinarians to decide which horses to deworm and when to deworm them," True said. "Our practice implemented routine fecal egg counts in horses over one year of age as part of our wellness program to encourage our clients to adopt responsible anthelmintic use."

Although Woodside's clients initially responded to the program's introduction with mixed opinions, True relayed that the overall response was very positive once the clients understood the process and how it benefited their horses and their bank accounts.

The clinic team divided the horses they examined into two classes: high shedders and low shedders. High shedders' fecal exams contained 300 eggs or more per gram of feces, while low shedders' feces contained less than 300 eggs per gram.

The basic program she and her colleagues outlined for low shedders (which accounts for the majority of the population, True said) includes deworming twice a year: once in December with moxidectin and praziquantel, and once in June with ivermectin and praziquantel. The specific dewormers used will likely vary in different parts of the country, she added.

The program the veterinarians recommended for high shedders includes five dewormer administrations per year. Moxidectin and praziquantel are used semiannually (in February and October). Oxibendazole, ivermectin and praziquantel, and pyrantel are used annually in May, June, and January, respectively. Again, the types of dewormers used should be appropriate for the region of the country.

About ten to 14 days post-deworming, True added, it's important to do a follow-up fecal egg count to ensure the amount of parasites present in the horse was reduced.

The veterinarians in the practice place foals on a specialized deworming program, according to True. In her program foals are first dewormed with oxibendazole when they're 6 to 8 weeks old, and they don't analyze a fecal sample before the first deworming. After the foal's first fecal sample is taken at 14 to 16 weeks, the foal is dewormed with pyrantel. Oxibendazole is used again at 22 to 24 weeks of age (again with no fecal sample). Finally, at 30 to 32 weeks, pyrantel is administered after a fecal examination. True recommends that the foal be put on a regular adult horse deworming schedule at 38 weeks.

True cautions not to use moxidectin to deworm foals less than 1 year old, as reports of death have surfaced due to accidental overdoses.

She said that the program Woodside established focuses on the parasites found in the Mid-Atlantic region (the clinic's location), and other areas of the country (or world) might have different parasite deworming requirements. Before creating such a program she suggests veterinarians develop a deworming schedule specific to their geographic location, and also that they analyze which types of dewormer should be used throughout the year in their region of the country.

Also, she cautioned that this program is not possible without appropriate staffing and time at the clinic to implement and process all the fecal samples.

By scheduling routine fecal exams for their horses, owners can feel confident they're following a personalized deworming program that meets their horse's individual needs. Additionally, True noted, some owners will save money by reducing the amount of dewormer they must purchase annually, which is a positive in the current economy.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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