Parasite control in horses has evolved over recent years to combat increasing drug resistance. Old recommendations suggested deworming every two months, but blind use of anti-parasitics has led to the resistance that we see today. To fight this, we now recommend just once or twice a year and annual fecal floats to evaluate the success of a treatment program. At our practice, we typically deworm twice a year, once with QuestPlus and once with regular Ivermectin. Annual fecal floats are important to do to evaluate the efficacy of the drugs we use.
The second way we have been fighting resistance is actually by allowing a very small number or common parasites to exist. Any grazing horse will inevitably have some level of parasite burden, and by not always deworming them, we allow for a more susceptible population to persist, we decrease the number of resistant parasites found in your horse’s GI tract, which means that when they have a higher parasite burden, the dewormers we have will be effective against them.
