West Nile virus causes severe neurological disease in horses with significant mortality and welfare impact. Vaccination is highly effective and represents a fundamental welfare protection.
West Nile virus encephalitis causes severe neurological suffering - horses with advanced disease are recumbent, unable to regulate posture, and may show signs of profound distress as neurological function deteriorates. Recovery cases require prolonged intensive nursing care including assistance standing, feeding support, and physical therapy that is both expensive and intensive. Vaccination is an exceptionally clear welfare case: a simple annual injection prevents a disease that causes severe suffering and approximately 35% mortality in unvaccinated infected horses. Failure to vaccinate horses against West Nile virus in endemic areas represents an avoidable welfare failure.