Headfly (Hydrotaea irritans) causes significant welfare problems in sheep during summer, with associated wound problems causing pain and secondary infection. Prevention and monitoring are the key welfare responses.
Headfly-affected sheep experience persistent irritation that disrupts normal behaviour and causes self-inflicted injury from repeated rubbing. The cycle of irritation leading to injury leading to more fly attraction creates progressive welfare deterioration that can be rapid in high-pressure conditions. Secondary blowfly strike of headfly-created wounds adds a layer of welfare harm through maggot feeding on living tissue. Affected sheep show reduced grazing time, increased agitation and social disruption as they attempt to escape the constant irritation. Prevention through insecticide application and good flock monitoring during summer is far more welfare-positive than treatment of established headfly damage.