Resistance to antiparasitic drugs in sheep and cattle nematodes is a growing welfare and production crisis, threatening the effectiveness of treatments that prevent significant suffering in livestock.
Anthelmintic resistance has a direct welfare impact: when drugs fail, parasites build to levels that cause anaemia, starvation, and death. Sheep with uncontrolled Haemonchus infections suffer extreme anaemia — pale gums, bottle jaw, and progressive debilitation are welfare indicators of severe disease. The welfare emergency drives farmers toward more frequent treatment, which accelerates resistance in a destructive cycle. Targeted selective treatment, refugia preservation, and integrated parasite management break this cycle while maintaining drug efficacy.