Anthelmintic resistance in the canine hookworm, Ancylostoma caninum

Hookworms are one of the most common soil-transmitted helminths and can infect a wide variety of mammals. There are three major anthelmintic drug classes currently available for treatment of hookworms in canines: the benzimidazoles, the tetrahydropyrimidines and the macrocylic lactones. In registration studies for the food and drug administration in the USA, febantel, moxidectin and milbemycin oxime all demonstrated efficacy of >99%. Fenbendazole demonstrated efficacy of >98% and pyrantel demonstrated a somewhat variable efficacy, with a mean across studies of approximately 94%, where more than half of those studies yielded >99%. The only mechanism of resistance currently known for anthelmintics is for the benzimidazole drugs. Detection of drug-resistant Ancylostoma caninum in dogs is a complex issue that deserves greater recognition before more multiple anthelmintic drug-resistant A. caninum infections are reported in an even wider geographic area and dog population distribution. Beyond the concerns for canine health, multiple anthelmintic drug-resistance in canine hookworms could present serious public health concerns because A. caninum is zoonotic.