Antiparasitic Drug Resistance and Sheep Welfare

Anthelmintic resistance in sheep parasites is reaching crisis levels in many countries, threatening the ability to control internal parasites that cause significant suffering in affected flocks.

Key Facts

Resistance to all three main classes of anthelmintics has been confirmed in sheep parasites in multiple countries
Haemonchus contortus -- barbers pole worm -- causes anaemia and death in affected sheep
Over-reliance on routine drenching has driven resistance development in many intensive sheep systems
Targeted selective treatment based on faecal egg count monitoring reduces resistance development
Alternative parasite control approaches include refugia management, copper oxide wire particles, and biocontrol fungi

Welfare Considerations

Anthelmintic resistance creates a future welfare emergency: as drug options narrow, effective parasite control becomes impossible using chemical means alone. Sheep with heavy parasite burdens experience significant welfare harm -- anaemia, bottle jaw, weight loss, and eventually death in severe cases. The cause of resistance is partly a welfare-driven paradox: treating all animals to prevent suffering in the most affected has accelerated resistance, threatening the ability to treat any animals effectively. Sustainable parasite control that preserves drug efficacy through targeted use is both a welfare strategy and an economic necessity. The transition requires significant changes in sheep farming practice that industry bodies and veterinary services are promoting but slowly achieving.

What You Can Do

Support sheep producers using targeted selective treatment rather than blanket drenching
Advocate for faecal egg count monitoring as standard practice in sheep welfare protocols
Donate to research into alternative parasite control methods including biocontrol approaches
Choose lamb and wool from producers with documented sustainable parasite management programmes