Deworming: One Size Doesn’t Fit All

Work with your veterinarian to develop an individualized deworming plan that caters to your horse’s needs.

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We all know each horse is different, so why treat them all with the same deworming schedule? Managing parasite control is a critical aspect of your horse’s health and should be adjusted depending on age, environment, season, and much more.

“Horse owners need to remember that parasites can cause illness in horses of all ages, and parasite resistance is real,” said Nathan Voris, DVM, equine technical services veterinarian for Zoetis. “It is up to individual horse owners and their veterinarians to take charge of this serious area of their horse’s health.”

It is important to take the parasite risk factors of each individual horse into consideration, including its age and health status, whether it travels and shows, and whether new horses are coming and going from the herd, Voris explained. This information can help you take control of the parasites in your horse and on your farm.

The American Association of Equine Practitioners (AAEP) recommends moving away from traditional deworming practices of treating the entire herd with the same dewormer at the same time. A few points Zoetis suggests remembering about individualized deworming:

  • Deworming programs should be designed for individual horses—forget the days of treating the group. Knowing each horse’s age, weight, and fecal egg count (FEC) results can help determine the most effective deworming plan for your horse.
  • AAEP Parasite Control Guidelines suggest a basic foundation of one or two dewormer treatments per year for every adult horse; Treatments should target large stongyles, small strongyles, tapeworms, bots, and stomach worms.
  • Roundworms or ascarids (Parascaris equorum) are recognized as a major parasitic pathogen in foals and weanlings, often causing poor growth. While roundworms have developed resistance to ivermectin, benzimidazoles and pyrantels remain effective. Daily dewormers can also be a good choice for adult horses with high strongyle contamination potential.
  • Deworming should take place based on the parasite’s life cycle so the medications are most effective in reducing the number of parasites in the environment. Spring and fall are the peak transmission seasons. • The wrong product at the wrong time can increase the population of anthelmintic-resistant parasites in your horse’s environment.
  • A FEC test is simple, inexpensive, and can tell you which individual horses are shedding more parasite eggs and should be dewormed more frequently. Evaluating treatments at least every three years with a fecal egg count reduction test can help determine product efficacy.

Proper parasite management is critical to your horse’s health. Collaborate with your veterinarian to develop an individualized deworming plan that caters to your horse’s needs.


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