Sheep Parasite Welfare: Liver Fluke and Worm Burdens

Parasite infestations are a major cause of disease, suffering and death in sheep worldwide. Understanding the welfare implications of parasitism and sustainable control strategies is essential for flock health.

Key Facts

Gastrointestinal nematodes cause production losses and welfare problems in virtually all sheep flocks
Liver fluke Fasciola hepatica causes acute and chronic liver damage causing significant mortality in wet years
Sheep with high worm burdens develop protein deficiency, lethargy, bottle jaw and eventually die
Anthelmintic resistance is a growing crisis with triple resistance reported in many UK flocks
FAMACHA scoring of lower eyelid mucous membranes allows targeted treatment of anemic individuals
Refugia-based strategies maintaining untreated sheep in the population slow resistance development
Strategic pasture management including rest periods reduces larval contamination and infection pressure
Integrated parasite management combining targeted treatment, refugia and monitoring reduces resistance development

Welfare Considerations

Parasite-induced suffering in sheep is chronic and often severe. Sheep with heavy worm burdens experience progressive protein malnutrition causing weakness, submandibular oedema and inability to compete for feed. The itching and discomfort of ectoparasites adds to the burden. Liver fluke infestation causes fever, abdominal pain and sudden death in acute cases, and progressive liver damage with anaemia and weight loss in chronic cases. The welfare impact is substantial and widespread - parasite problems affect the majority of sheep flocks to some degree. Anthelmintic resistance threatens to remove the primary tool for parasite control, making sustainable management strategies essential for both welfare and the long-term viability of sheep farming.

What You Can Do

Support development and adoption of integrated parasite management strategies in sheep farming
Advocate for veterinary prescription requirements for anthelmintics to support responsible use
Choose lamb products from farms demonstrating sustainable parasite management approaches
Donate to veterinary research programs developing resistance-beating parasite control strategies
Support Moredun Research Institute and Animal Health and Welfare Board programs
Engage with farming communities about the long-term welfare implications of anthelmintic resistance