Resistance to anthelmintic (worming) drugs in sheep and cattle parasites is a growing welfare crisis. As treatments fail, parasitic disease causes increasing suffering while producers are left with fewer options.
Anthelmintic resistance creates a welfare crisis that unfolds slowly but inexorably. As drugs lose efficacy against farm nematodes, the parasite burden on animals increases and the tools to reduce it become less effective. Heavily parasitised sheep suffer from protein deficiency (parasites steal blood and protein from the gut), anaemia, immunosuppression and in severe cases death from haemonchosis (blood-sucking worm infection). The welfare trajectory in a flock where resistance is not managed is toward increasing, less-treatable parasitism. Refugia management and targeted selective treatment are welfare-preserving strategies that maintain the efficacy of remaining treatment options.