Liver Fluke and Internal Parasite Burden in Sheep

Internal parasites like liver fluke cause significant suffering in sheep worldwide, with welfare implications extending across millions of animals annually.

Key Facts

Liver fluke (Fasciola hepatica) infects over 300 million sheep globally
Fluke causes bile duct damage, anaemia, weight loss and death in severe cases
Haemonchus contortus (barbers pole worm) kills hundreds of thousands of lambs annually
Anthelmintic resistance is growing — up to 90% of farms have resistant worm populations
FAMACHA scoring allows targeted treatment based on eye membrane colour (anaemia indicator)
Refugia-based strategies preserve susceptible worm populations to slow resistance
Wet conditions and poor drainage dramatically increase fluke risk on farms

Welfare Considerations

Internal parasites are among the most significant welfare challenges in sheep production. Infected animals experience chronic pain, malnutrition, anaemia and debilitation. Heavily parasitised lambs may suffer for weeks before death. The growth of anthelmintic resistance means traditional blanket treatments are failing, requiring smarter targeted approaches. Regular FAMACHA assessment, strategic drenching, pasture management, and refugia-based control can protect both welfare and the long-term effectiveness of treatments.

What You Can Do

Support farms that use integrated parasite management rather than blanket drenching
Ask wool and lamb suppliers about their parasite monitoring programs
Advocate for veterinary access in developing countries where parasites kill livestock
Support research into vaccines against Haemonchus and liver fluke
Learn about refugia-based strategies that preserve drug efficacy while protecting welfare