The American Association of Equine Practitioners (AAEP) has revised their guidelines on parasite control. An individualized risk-based deworming approach begins with a fecal egg count (FEC) test. Your veterinarian evaluates FEC test results before and after deworming to help determine a baseline for parasite levels and efficacy of the treatment.
Once your horse’s risk level is established, deworming treatments should be focused in the season of peak transmission, such as spring and fall when pasture refugia, or parasite populations, are at their highest.
Parasites can become resistant to deworming active ingredients when they are overexposed to them, leaving fewer treatment options. Small strongyles have been shown to have widespread resistance to fenbendazole. Moxidectin is the most effective treatment against small strongyles, but its use should be timed to control levels of egg shedding into the environment in the fall, when environmental conditions are conducive to egg development and larval survival.
Because every horse is unique, the AAEP guidelines recommend working with your veterinarian to develop an individualized risk-based deworming plan tailored to your horse’s needs.