Farm Animals

Sheep Internal Parasite Resistance Management

Anthelmintic resistance in sheep gastrointestinal nematodes is a major and growing challenge requiring strategic management to protect welfare.

Key Facts

Resistance to all major anthelmintic classes is documented in UK sheep farms
Blanket treating all animals at fixed intervals has driven resistance development
Targeted selective treatment using FAMACHA and fecal egg counts preserves efficacy
Refugia - maintaining some untreated animals - slows resistance development
New anthelmintic classes are limited, making resistance management critical

Welfare Considerations

Heavy worm burdens cause significant welfare harm through diarrhoea, weight loss, anaemia and death. Anthelmintic resistance threatens the ability to treat effectively, risking return to pre-anthelmintic welfare conditions. Strategic resistance management preserves treatment options essential for future welfare protection.

What You Can Do

Implement targeted selective treatment using FAMACHA and fecal egg counts
Avoid importing resistance through quarantine treatments of bought-in stock
Work with your vet to develop a flock parasite management strategy