Deworming Programs




Recent research has shown that 80 percent of the parasite egg population comes from 20 percent of the equine population on a given farm, indicating most horses have very low parasite burdens.  Parasite resistance to dewormers is increasing and no new classes of dewormers are currently being developed.  Colts Head Veterinary Services will help you:

  1. Determine if your horse is a low, moderate, or high shedder of GI parasites.
  2. Use a dewormer that is effective for your horse.
  3. Decrease your horse’s exposure to parasites.

To accomplish these goals we recommend the following plan:
  1. To begin, we need to determine your horse’s parasite burden:
    • An initial fecal egg count should be performed at least 6-8 weeks after deworming with pyrantel pamoate (Strongid) or 10-12 weeks after deworming with ivermectin (Zimectrin) or moxidectin (Quest). This will determine if your horse is a low, moderate, or high shedder of GI parasites.  A deworming program will be recommended.
  2. Next, we need to find dewormers that are effective for your horse:
    • Deworm your horse with the recommended product. 
    • Have a fecal egg count performed 10 to 14 days after deworming to make sure the parasites were killed.  This step is very important to determine if the dewormer was effective and we may modify the deworming schedule based on these results.
    • Repeat this procedure the first time either ivermectin or moxidectin is used and again when pyrantel pamoate is administered- a fecal egg count performed before deworming, deworm your horse, and repeat a fecal egg count 10 to 14 days later. This procedure is performed once with ivermectin/ moxidectin and once with pyrantel pamoate.
    • After the first year on this program, only an annual fecal egg count is necessary.
  3. Decrease your horse’s exposure to parasites: 
    • Remove manure from paddocks twice weekly if possible. 
    • If you are going to drag or mow paddocks, wait until the hottest days of the year, drag or mow, and then leave the paddock vacant for several weeks or drag at the end of the grazing season. 
    • If possible, rotate pastures with other species of grazing animals.

Colts Head Veterinary Services also has a recommended deworming program if you are not interested in deworming based on fecal parasite egg counts or if your horse is less than a year of age.