Equine influenza and other respiratory diseases spread rapidly through horse populations, causing significant welfare impacts. Vaccination and biosecurity prevent most outbreaks.
Respiratory disease in horses causes welfare impacts beyond the immediate illness. Horses with influenza experience high fever, muscle pain, profound weakness, and distress lasting 1-2 weeks. Competition horses inappropriately returned to work during or after illness risk permanent reduction in respiratory capacity. Equine herpesvirus neurological disease (EHM) causes rapid onset weakness and paralysis - affected horses may be unable to rise and face euthanasia. The welfare case for vaccination is clear: preventing severe clinical disease reduces suffering duration and intensity even when vaccination does not fully prevent infection. Biosecurity at high-risk events - isolation of new arrivals, monitoring for fever, avoiding nose-to-nose contact - further reduces transmission risk.