Anthelmintic resistance in sheep gastrointestinal nematodes is a growing crisis that undermines the effectiveness of parasite control and poses long-term welfare risks.
Gastrointestinal parasites cause anaemia, weight loss, bottle jaw, diarrhoea and death in affected sheep. As anthelmintic resistance increases, these conditions will become harder to treat. A transition to targeted selective treatment - treating only animals that actually need treatment based on clinical signs and egg counts - preserves drug efficacy and reduces suffering.