Reviewing AAEP Parasite Control Guidelines

If you’re still recommending rotational treatment with anthelmintics at regular intervals to horse owners for parasite control, it’s time to familiarize yourself with AAEP’s new guidelines, which were updated in 2019. Previous parasite control guidelines were based on 55-year-old research that’s no longer valid and could be harmful to horse populations in the long run. Here’s what to know about the new guidelines.

3 Goals of Parasite Control

The AAEP acknowledges that there’s no one-size-fits-all approach to parasite control in equids. However, all parasite control programs should have the same goals, which do not include total parasite eradication.

“The true goal of parasite control in horses is to limit parasite infections so animals remain healthy and clinical illness does not develop,” according to AAEP Internal Parasite Control Guidelines. “The goal is NOT to eradicate all parasites from a particular individual. Not only is eradication impossible to achieve, [but] the inevitable result is accelerated development of parasite drug resistance.”

Instead, the AAEP recommends a parasite control program have these three goals:

  1. Minimize the risk of parasitic disease.
  2. Control parasite egg shedding.
  3. Maintain efficacious drugs by avoiding anthelmintic resistance as much as possible.

Control Methods

The AAEP recommends horse owners take the following steps to control parasitic disease and thus should be the basis of your recommended parasite control plan:

  • Perform regular fecal egg count (FEC) testing and fecal egg count reduction testing (FECRT) via the Modified McMaster or Modified Wisconsin testing techniques.
  • Environmental control, including the swift removal of manure from pastures. 
  • Proper composting of manure and soiled bedding.
  • Administer preventive anthelmintic treatments, such as benzimidazoles, tetrahydropyrimidines or macrocyclic lactones, at times of the year when transmission rates tend to be highest (when temperatures are moderate). The AAEP does not recommend the use of alternative dewormers that are not FDA approved.

FEC testing and FECRT frequency depends on the equid’s age. In young horses, FEC testing should be performed at weaning and FECRT should be conducted annually until age 3. The AAEP recommends evaluating anthelmintic treatment efficacy with FECRT in mature horses every three years.

For more advice on building a parasite control program, read the full AAEP Internal Parasite Control Guidelines.