Parasites can cause colic in a number of ways like burrowing into tissue linings and intestines, releasing gut irritants, and damaging organs as they travel through the bloodstream. The best way to control parasite infestations and prevent resistance to dewormers is to monitor individual horse fecal egg counts and strategically deworm for the specific parasites identified. Strategic deworming benefits both horse and owner. By individualizing deworming strategies, one minimizes parasite contamination of the environment, improves individual horses’ overall health, and limits parasite resistance. Owners save money by strategically deworming only affected horses. Regular, yearly deworming is still recommended for certain parasites, such as tapeworms, that cannot easily be detected on a routine fecal exam. Working with your veterinarian is recommended in order to determine the best protocol for your farm.

Deworming protocols for young stock need to be tailored to individual farms. Because ascarids can cause significant problems in young stock, deworming strategies for foals and weanlings should include dewormers that kill adult and larval ascarids. When developing a deworming plan, consider the stocking density, number of years housing horses, age of individual horses, resistance on the farm, ascarid numbers, and previous deworming protocols.

Depending on the parasite and time of year, many parasites do not reach maturity in the gastrointestinal tract for several months. Therefore, fecal egg counts will not accurately determine the number of parasitic larvae migrating through the horses’ bodies. Larvicidal dewormers are recommended when treating prior to maturation of adult worms. Resistance may impact efficacy of different products.

The MSU Veterinary Medical Center’s Equine Services team takes pride in creating customized and effective deworming plans for each patient. We identify your horse’s parasite load through a fecal sample.

  • Our laboratory technicians will determine if your horse is a low, moderate, or high parasite egg shedder.
  • We create a customized deworming plan for your horse and farm. This plan will take into account quantity and type of fecal eggs, the horse’s age, housing and environment, date of last deworming, and type of dewormer that was used. As parasite resistance is a major concern, dewormers need to be evaluated for efficacy.  On some farms, only one or two dewormers may be effective in controlling a certain parasite.

Minimize your horse’s expose to parasites by:

  • Don’t overpopulate your pasture with too many horses. Rotate their grazing between pastures.
  • If possible, remove all feces from the pasture at least two times per week. Alternatively, dragging the pasture to break up fecal piles on a hot, sunny day and allowing time for them to dry out will aid in parasite control.
  • Only spread compost—not raw manure—on the pasture.