Antiparasitic Resistance

Comment on this policyScientific experts have identified changes in parasitic infections (relating to parasite genetics, biology, and robustness as well as management of these parasites) and in parasiticide susceptibility that are of immediate and emerging concerns in many species. The AVMA strongly recommends that veterinarians in concert with animal owners utilize the most up-to-date guidelines, treatments, and evidence-based medicine for parasite control. Animal owners should always consult their veterinarian about parasite control. Examples of parasites that have evidence of resistance to certain parasiticides include Dirofilaria immitis (heartworm) in dogs; Haemonchus contortus (barber pole worm), Teladorsagia circumcincta (stomach worm), and Trichostrongylus colubriformis (black scour worm) in small ruminants; Cooperia spp. (intestinal worm) in cattle; and Cyathostomin spp. (small strongyle) and Parascaris equorum (roundworm) in horses.

These changes are affecting the health and productivity of animals, requiring veterinarians and animal owners to reexamine strategies, programs, and drug choices for parasite evaluation and control. The geographical extent of parasite species with documented parasiticide resistance varies greatly and treatment strategies should be guided by local conditions and experience. Diagnosis of the presence of parasiticide resistance is still challenging. Primary and continuing educational efforts in the field of parasitology are needed to provide the most up-to-date knowledge to veterinarians, veterinary students, and animal owners; this knowledge should include parasite life cycles, diagnostic evaluations, and treatment and control measures. In developing a parasite control program, veterinarians can obtain specific information from multiple sources including, but not limited to, species and specialty groups, government agencies, and other experts.