Livestock Fly Strike and Myiasis: Preventing Blowfly Infestation in Sheep

Flystrike — blowfly larvae infesting live animal tissue — is one of the most acutely painful welfare conditions in sheep farming, affecting hundreds of thousands of animals annually.

Key Facts

Blowfly strike in the UK alone affects approximately 1.5-3% of sheep each year, causing significant suffering and economic loss.
Blowflies lay eggs in soiled or damp wool; larvae hatch within hours and begin consuming live tissue almost immediately.
An untreated struck sheep can have thousands of maggots consuming its flesh within days, causing extreme pain and tissue destruction.
Early detection is critical: strike can advance from eggs to severe tissue damage within 72 hours in warm weather.
Preventive insecticides, crutching (removing wool around the hindquarters), and selective breeding for reduced breech wrinkle significantly reduce risk.
Mulesing — removing skin folds around the hindquarters — is used in Australia to prevent strike but itself causes acute pain without anaesthesia.
Fly-sensing electronic ear tags are an emerging technology enabling farmers to detect early signs of strike through behavioural change alerts.

Welfare Considerations

A sheep with advanced flystrike is experiencing extreme suffering. The sensation of thousands of maggots consuming live tissue, combined with the toxins released by larval feeding, causes intense pain, restlessness, and systemic illness. Without treatment, affected sheep deteriorate rapidly and die. The condition is entirely preventable with appropriate monitoring and management — but sheep in large, extensive flocks may go unobserved long enough for minor strike to become life-threatening. Prevention requires investment in regular inspection, particularly during warm humid weather, targeted preventive treatment, and wool management to reduce strike risk sites. The existence of technological solutions including electronic monitoring reinforces that prolonged flystrike suffering reflects management failure, not unavoidable risk.

What You Can Do

Ensure sheep are checked thoroughly for flystrike at least twice weekly during warm weather seasons.
Use preventive insecticide treatments in high-risk periods, following veterinary guidance on appropriate products.
Manage wool hygiene through crutching to remove soiled fleece around vulnerable areas.
Treat struck sheep immediately with appropriate insecticides and veterinary care.
Support research into electronic monitoring technologies that enable earlier flystrike detection in extensive flocks.