Haemonchus contortus is the most pathogenic internal parasite of small ruminants globally, causing anaemia, bottle jaw, and death with significant welfare impacts on affected animals.
Haemonchus infestation causes progressive welfare compromise through blood loss leading to anaemia, weakness, and eventually collapse. Affected animals are too weak to graze effectively, suffer from the discomfort of oedematous swelling (bottle jaw), and deteriorate rapidly without treatment. The welfare impact is particularly severe in late-pregnant ewes and young lambs. Evidence-based parasite control using FAMACHA scoring, targeted selective treatment, and refugia management reduces anthelmintic resistance while maintaining effective welfare protection for clinically affected animals.