Farm Animals

Sheep Internal Parasite Management and Resistance

Internal parasites, particularly Haemonchus contortus, are a major welfare challenge in sheep, with anthelmintic resistance making management increasingly difficult.

Key Facts

Nematodirus battus causes spring diarrhoea in lambs with high mortality potential
Haemonchus contortus causes anaemia and can kill quickly in hot, wet conditions
Resistance to all three anthelmintic drug classes has been confirmed globally
FAMACHA scoring identifies anaemia in individual sheep to target treatment
Refugia-based treatment strategies preserve drug efficacy by reducing selection pressure

Welfare Considerations

Parasitism causes suffering through anaemia, protein loss, diarrhoea, and reduced growth. Deaths from parasitic gastroenteritis involve prolonged suffering. As anthelmintic resistance spreads, maintaining drug efficacy through targeted selective treatment is both a welfare and long-term management priority.

What You Can Do

Support farms using FAMACHA and targeted selective treatment protocols
Advocate for Responsible use of anthelmintics to preserve efficacy
Choose lamb products from farms with parasite management plans