Anthelmintic resistance in equine parasites is a growing welfare challenge requiring strategic, diagnostic-based worming programs rather than routine blanket treatment.
Worm burdens cause significant welfare harm in horses - heavy infestations cause weight loss, diarrhea, colic, and in severe cases intestinal rupture or larval cyathostominosis. The latter is particularly severe, causing acute hemorrhagic diarrhea and high mortality from the mass emergence of encysted larvae from the gut wall. As resistance to available wormers grows through overuse, the ability to effectively control these parasites is being eroded. Strategic worming programs based on diagnostic testing protect both individual horse welfare through effective treatment and the population welfare by preserving the efficacy of available treatments for future generations.