Flystrike (myiasis) is a devastating condition in sheep caused by blowflies laying eggs in fleece, causing larvae to burrow into living tissue. Prevention is the priority for sheep welfare.
Flystrike causes one of the most acutely painful conditions in farm animals. Larvae burrowing into living tissue while the animal remains alive constitutes severe suffering. Affected sheep often separate from the flock, become lethargic, and stop feeding. Without treatment, systemic infection and death follow. The welfare calculus of mulesing — causing acute pain during the procedure to prevent potentially greater suffering from flystrike — has been intensely debated. New Zealand banned mulesing and has invested in alternative solutions including breeding programs selecting for bare-breech sheep. Chemical protection using pour-on insecticides provides effective prevention without surgical intervention. Daily checking during peak blowfly season is essential welfare practice.