Anthelmintic Resistance in Companion Animal Parasites: Diagnostic and Treatment Challenges.

Anthelmintics are central to parasite control in companion animals, but drug targets in helminths remain limited. Anthelmintic resistance is a clinically significant threat, with emerging multiple anthelmintic drug-resistant Ancylostoma caninum, macrocyclic lactone-resistant Dirofilaria immitis and praziquantel-resistant Dipylidium caninum. Each treatment is a selection event which eliminates susceptible parasites and enriches resistant survivors. Drug-resistant helminths often go undetected due to limited diagnostics and sole reliance on treatment. While some molecular tools can detect gene polymorphisms associated with resistance, their use is somewhat limited. Sustainable control will require strategic evidence-based use, targeted surveillance, and continued research into resistance mechanisms and detection tools.