Livestock

Anthelmintic Resistance in Sheep: A Growing Welfare Crisis

Welfare analysis of anthelmintic resistance in sheep parasites -- a growing threat to effective parasite control.

Key Facts

Resistance to all three major anthelmintic drug classes is widespread in sheep nematode populations in the UK
Haemonchus contortus (barber pole worm) causes acute anaemia and death -- resistance makes control extremely difficult
Resistance develops through overuse and misuse of anthelmintics -- under-dosing and repeated use of the same drug class
The SCOPS (Sustainable Control of Parasites in Sheep) guidelines provide evidence-based resistance management
Targeted selective treatment (treating only animals requiring medication) slows resistance development
Refugia management -- leaving some untreated animals as reservoir for susceptible worm genetics -- is central to resistance control
Faecal egg count reduction testing is the gold standard for monitoring anthelmintic efficacy on farm
Welfare implications of resistance are severe -- untreatable parasite burdens cause chronic disease and death

Welfare Significance

Anthelmintic resistance is a slow-moving welfare crisis in sheep farming. As effective treatments fail, sheep face parasite burdens that cannot be adequately controlled -- causing chronic suffering from anaemia, ill-thrift, and diarrhoea. Responsible anthelmintic use is both a welfare imperative and a farm business necessity. Preserving drug efficacy is preserving the welfare tools available to future generations of farmers.

What You Can Do

Implement SCOPS targeted selective treatment protocols rather than routine whole-flock treatment
Monitor anthelmintic efficacy with faecal egg count reduction tests annually
Rotate drug classes appropriately and avoid under-dosing -- always dose by weight
Consult your vet about refugia management and on-farm resistance testing