What is a good deworming program for horses?

Parasite management in horses has evolved significantly over the past fifteen years from the calendar-based rotational deworming programs that were the previous standard toward a targeted selective treatment approach that is now recommended by the majority of equine veterinary organizations and parasitologists. Understanding the principles behind this shift — and what a good modern parasite management program actually involves — helps horse owners make more effective decisions about deworming rather than following outdated protocols that contribute to anthelmintic resistance without necessarily managing parasites effectively. Fecal egg count testing is the foundation of targeted selective deworming. A fecal egg count — a laboratory analysis of a fresh manure sample that quantifies the number of parasite eggs being shed per gram of manure — allows the veterinarian or owner to categorize each horse as a low, moderate, or high shedder and to make deworming decisions based on that specific horse's parasite burden rather than on a calendar-based protocol that treats all horses the same regardless of their actual parasite load. Low shedders — which research consistently shows constitute the majority of horses in most populations — can often be dewormed far less frequently than the previous standard without any compromise in parasite control, while high shedders are treated more aggressively. This targeted approach dramatically reduces the total anthelmintic exposure in the horse population, which slows the development of drug resistance in parasite populations. Fecal egg count reduction testing — performing a fecal egg count before treatment and then again two weeks after treatment — confirms whether the specific anthelmintic used is actually working against the specific parasites present in a specific horse. Resistance to ivermectin and other anthelmintics has been documented in horse parasite populations globally, and a drug that worked reliably a decade ago may not be working reliably today in a specific geographic region or a specific horse. Confirming efficacy through reduction testing rather than assuming it allows treatment protocols to be adjusted when resistance is detected. A veterinarian familiar with the current evidence on equine parasite management is the most appropriate resource for designing a specific program for a specific horse or a specific property, because the specific parasites present, the local resistance patterns, and the management factors of the specific situation all influence what an effective targeted program looks like in practice.