Equine influenza is a highly contagious respiratory virus that causes significant illness, disrupts competition programmes and causes welfare impacts in unvaccinated horse populations.
Equine influenza causes a respiratory illness that horses experience as profound systemic malaise - high fever, muscle pain, nasal discharge and exhaustion that makes even standing uncomfortable. The requirement for complete rest during and after the acute phase reflects the severity of the illness and the risk of myocarditis and permanent cardiac damage from premature return to work. Outbreaks in unvaccinated populations spread rapidly through equine events, affecting many animals simultaneously. The welfare cost of preventable influenza outbreaks is significant both in individual animal suffering and in the disruption to welfare management that mass illness creates.