The headfly (Hydrotaea irritans) is a significant welfare pest for sheep in the UK and northern Europe, causing head wounds, fly strike and secondary infections.
Headfly infestation causes persistent, distressing welfare harm to affected sheep. The constant irritation of fly feeding, the open wounds that develop from chronic attack, and the pain of secondary infections and fly strike represent significant suffering that can continue for weeks without intervention. Welfare-focused sheep management includes regular monitoring for headfly activity especially in summer, prompt treatment of wound sites, and use of appropriate preventive measures. The move toward polled breeds removes a key site for headfly feeding.