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New AAEP Internal Parasite Control Guidelines

In May 2024, the American Association of Equine Practitioners (AAEP) released revised Internal Parasite Control Guidelines. The updated guidelines address Small Strongyles, Large Strongyles, Tapeworms, Roundworms (Ascarids), Threadworms, Pinworms, Bots, Stomach Worms (Habronema), and Neck Threadworms.

The complete set of these practical guidelines, designed for your convenience, is readily accessible here:

As a horse owner, it's essential to understand that parasite control is not about eliminating all parasites from your horse. Instead, the aim is to keep your horse healthy and minimize the risk of clinical illness. Recognizing that complete eradication of equine internal parasites is not feasible, and by avoiding such an unrealistic goal, we can collectively address the challenge of drug resistance in equine parasites that has emerged in recent years.

Fecal Egg Count Reduction Tests - Why They Are So Important?

Numerous horse owners may not understand the significance of Fecal Egg Count Reduction Tests (FECRT). These tests do not indicate the quantity of worms present in a horse or whether the worms are impacting the horse's well-being. Nonetheless, they provide insight into the effectiveness of the dewormers employed in our parasite management regimen, what types of worms are present, and whether the horse is a high, medium, or low shedder. This information is crucial for ensuring the efficacy of our parasite control measures.

Regrettably, the escalating global issue of drug resistance in equine internal parasites poses a significant concern. Equine dewormers are categorized into three common classes: benzimidazoles (fenbendazole, oxibendazole), pyrimidines (pyrantel pamoate), and macrocyclic lactones (ivermectin, moxidectin). Horse owners commonly base their dewormer selection on the information provided on the dewormer box, opting for a product that purports to address the specific worms they intend to treat.

Unfortunately, the information provided on the packaging of the dewormer purchased from your local equine supply store is significantly outdated. Consequently, it does not offer valuable guidance in choosing the appropriate dewormer for your horse. Here is the current resistance status for the prevalent internal parasites in equines:

Small Strongyles

  • Fenbendazole: Widespread Drug Resistance

  • Oxibendazole: Widespread Drug Resistance

  • Pyrantel pamoate: Widespread Drug Resistance

  • Ivermectin: Emerging Drug Resistance

  • Moxidectin: Emerging Drug Resistance

Roundworms (Ascarids)

  • Fenbendazole: Emerging Drug Resistance

  • Oxibendazole: Emerging Drug Resistance

  • Pyrantel pamoate: Emerging Drug Resistance

  • Ivermectin: Widespread Drug Resistance

  • Moxidectin: Widespread Drug Resistance

Large Strongyles 

  • Fenbendazole: None

  • Oxibendazole: None

  • Pyrantel pamoate: None

  • Ivermectin: None

  • Moxidectin: None

To effectively address your horse's internal parasites, it is recommended you establish a strong relationship with your veterinarian. By adhering to the latest AAEP Internal Parasite Deworming Guidelines, your veterinarian can assist in formulating a comprehensive plan encompassing testing schedules, result interpretation, dewormer selection, strategies for combating drug resistance, and tailored recommendations based on your horse's age and specific requirements.

Learn more about FECRTs in the video below by Equine Parasitologist Dr. Martin Nielsen from the University of Kentucky's Gluck Equine Research Center.

Key Take-Home Messages from the new AAEP Internal Parasite Control Guidelines:

  • Conduct annual fecal egg count reduction tests (FECRT) on all horses to ensure the efficacy of dewormers being used.

  • Understand that no dewormer can completely eradicate all parasites in a horse.

  • To minimize pasture contamination, maintain periodic fecal egg counts (FEC) once or twice a year to categorize horses as low, medium, or high shedders.

  • Deworm all horses at a standard rate (once or twice a year) and focus on more frequent deworming for specific horses based on FEC results (high shedders of strongyles).

  • Avoid using FECs as a diagnostic tool for diseases in horses, as there is no direct link between FECs and disease-causing parasite life stages.

  • Discontinue the practice of deworming all horses at fixed intervals throughout the year (e.g., every two months) and refrain from rotating dewormers blindly.

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Jul 13
Rated 3 out of 5 stars.

A nice study but what does it bring us in more healthy Friesian horses in the near future. Research should be done in the real practice today by asking Equine Vets and Equine Hospitals what the biggest problems are and go from there ! Take the University researchers outside and let them feel the real problems in the field. For me and many other specialists, the one and only way to go is: controled OUT-cross !!


Ben Horsmans Equine Vet and Friesian Breeder with Van de Velde Friesians (!)(Sape/Barteld/Walter)

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