Farm Animal Welfare

Farm Sheep: Internal Parasite Refugia Management

Anthelmintic resistance in sheep roundworms is widespread, and refugia-based management preserves treatment efficacy while maintaining welfare protection.

Key Facts

Resistance to multiple drug classes is now common in Haemonchus contortus and other sheep roundworms
Refugia refers to the proportion of worm populations not exposed to treatment
Treating all sheep simultaneously eliminates susceptible worms, selecting rapidly for resistant populations
Targeted selective treatment based on FAMACHA scoring or faecal egg counts preserves refugia
Quarantine treatment of incoming sheep with a combination drench prevents resistance introduction

Welfare Considerations

Anthelmintic resistance eliminates the welfare protection that effective parasite treatment provides. When treatment fails, sheep experience progressive parasitism with anaemia, weight loss, bottle jaw, and death. Preserving treatment efficacy through refugia management is therefore direct welfare protection - maintaining the tools that prevent parasitic disease suffering in the future.

What You Can Do

Implement faecal egg count testing to guide treatment decisions rather than calendar dosing
Quarantine and treat all incoming sheep before mixing with resident stock
Work with your vet to conduct periodic faecal egg count reduction tests to check for resistance
Avoid under-dosing by weighing animals and calibrating drenching equipment
Participate in regional resistance monitoring programmes