Internal and external parasites cause significant welfare problems in dogs, but inappropriate or excessive parasite treatment also carries risks that require evidence-based management approaches.
Parasite-related welfare problems in dogs range from mild gastrointestinal discomfort from light worm burdens to life-threatening disease from lungworm infection or heavy tick-borne pathogen loads. The welfare of dogs at significant parasite risk is substantially improved by appropriate preventive treatment. However, the over-treatment of dogs at low actual risk with broad-spectrum antiparasitic products contributes to resistance development and unnecessarily exposes dogs to chemical treatments with their own safety profiles. Evidence-based parasite management using risk assessment, targeted treatment, and monitoring is the approach most beneficial to individual dog welfare while also preserving treatment effectiveness for the future.