Sheep Flystrike: Blowfly Strike Prevention and Welfare

Flystrike (myiasis) is one of the most painful and distressing conditions in sheep. Blowfly larvae eat living tissue, causing severe suffering and rapid death without prompt treatment.

Key Facts

Flystrike occurs when blowflies (Lucilia cuprina in Australia, Lucilia sericata in the UK) lay eggs on sheep, and hatching larvae burrow into the skin.
Larvae release toxins and enzymes as they feed on living tissue, causing rapidly expanding lesions, toxemia, and death within days.
Risk factors include dag (fecal contamination) around the tail, skin wounds, foot rot lesions, and warm, humid weather.
Australia, New Zealand, and the UK are particularly affected; Australian flystrike alone causes losses estimated at AUD 280 million annually.
Mulesing — surgically removing skin folds around the tail — has been used to reduce dag accumulation and flystrike risk in Merino sheep, but causes significant acute pain.
Alternatives to mulesing include selective breeding for plain-bodied sheep, dag management, and preventive insecticide treatments.
Rapid detection is critical — affected sheep may be struck before signs are apparent, emphasizing the importance of frequent inspection.

Welfare Considerations

Flystrike causes extreme suffering. Affected sheep experience intense pain, irritation, and systemic toxicity as larvae consume living tissue. By the time obvious signs appear — a characteristic damp, darkened fleece over the affected area, or obvious distress behaviors — the lesion may already be extensive. Death from untreated strike can occur within 3-4 days. The welfare case for prevention — through breeding, dag management, and appropriate preventive treatments — is overwhelming. Mulesing, while reducing flystrike risk, causes significant acute pain and is increasingly criticized. The availability of effective non-mulesing alternatives means the welfare trade-off is no longer necessary. Regular inspection of sheep, particularly in high-risk weather conditions, is a basic welfare obligation for sheep farmers.

What You Can Do

Inspect sheep daily during warm weather, paying particular attention to the tail and breach area.
Implement a dag management program — regular crutching (shearing around the tail) reduces flystrike risk.
Use veterinary-approved preventive treatments during high-risk seasons, following label instructions.
Support breeding programs that select for plain-bodied, low-dag Merino sheep as an alternative to mulesing.
Treat flystruck sheep immediately — use a flystrike spray to kill larvae and contact your vet for assessment.
Advocate for welfare labelling of wool products that indicates whether mulesing was used in production.