Equine Herpesvirus: Welfare Impact of EHV-1 Outbreaks and Prevention

Equine herpesvirus type 1 (EHV-1) causes respiratory disease, abortion storms, and devastating neurological disease in horses. Prevention through vaccination and biosecurity is the best welfare protection.

Key Facts

EHV-1 causes four distinct disease syndromes: respiratory disease, abortion, neonatal death, and equine herpesviral myeloencephalopathy (EHM)
EHM - the neurological form - can cause sudden-onset ataxia, paralysis, and bladder dysfunction with high fatality and welfare concerns
EHV-1 can be transmitted by direct contact, respiratory secretions, and fomites; the virus persists in the environment for weeks
Major outbreak events at equestrian competitions (2021 Valencia and other events) resulted in hundreds of cases and deaths across multiple countries
Vaccination reduces respiratory disease and abortion but does not reliably prevent EHM - this limitation frustrates welfare-focused management
Quarantine of exposed horses and event cancellation are the primary outbreak control measures
Most horses carry latent EHV-1 that can reactivate under stress - competition, transport, and mixing are known triggers
Testing including nasal swabs and blood samples can identify shedding horses during outbreaks

Welfare Considerations

EHV-1 outbreaks create acute welfare crises in equestrian communities. The neurological form (EHM) is particularly devastating - horses may progress from normal to recumbent within hours, with many unable to rise. Recumbent horses require intensive nursing care and face serious injuries from repeated attempts to rise. The fatality rate in EHM is significant, and horses that survive may have lasting neurological impairment. The welfare of horses in outbreak situations extends beyond directly affected animals - biosecurity quarantine prevents affected horses from receiving normal care and social contact. The equestrian community's challenge is balancing competitive and training objectives against the risk of amplifying virus spread through horse movement and competition events. Event organizers and riders sharing biosecurity responsibility is essential for welfare protection.

What You Can Do

Vaccinate your horses against EHV-1 according to your vet's recommendations, including mares before breeding and high-risk sport horses
Implement strict biosecurity when returning from competitions: isolate horses for 21 days and monitor for signs
Learn EHM recognition: sudden ataxia, hindlimb weakness, urinary incontinence, or recumbency requires immediate veterinary attention
Report suspected EHM or respiratory disease clusters immediately to your vet and relevant equestrian authorities
Support event cancellation decisions when EHV outbreaks threaten - disruption to competition is preferable to outbreak amplification
Maintain good stable ventilation and reduce unnecessary stress that can trigger latent EHV reactivation
Follow biosecurity protocols when visiting studs or equestrian facilities during high-risk periods
Support EHV surveillance programs that enable rapid outbreak detection and response