Equine Herpesvirus: Disease, Welfare and Biosecurity in Horse Populations

Equine herpesvirus is endemic in horse populations worldwide and can cause respiratory disease, abortion, and neurological illness. Understanding biosecurity protects both horse welfare and equestrian activities.

Key Facts

Equine herpesvirus types 1 and 4 are the most common and clinically significant of the nine equine herpesviruses
EHV-1 can cause respiratory disease, abortion storms in broodmare herds, and rarely neurological disease
The neurological form, equine herpesvirus myeloencephalopathy, can cause severe ataxia and paralysis
Up to 80 per cent of horses are latently infected with EHV-1 and can shed virus during stress or immunosuppression
Outbreaks at equestrian events have led to mass quarantines and cancellations of major competitions
Vaccination is available but does not fully prevent infection, only reducing clinical severity and viral shedding
Biosecurity measures including nose-to-nose contact prevention are critical for controlling disease spread

Welfare Considerations

Equine herpesvirus causes significant welfare impacts through acute respiratory illness, pregnancy loss in mares, and devastating neurological disease in affected horses. The neurological form causes severe ataxia, recumbency, and bladder dysfunction that often necessitates euthanasia on welfare grounds. Horses with respiratory EHV disease experience fever, nasal discharge, and malaise requiring supportive care and rest. Welfare impacts extend beyond individual animals to disrupt herd dynamics through quarantine and movement restrictions that prevent normal social access and turnout. Biosecurity education for horse owners and competition organisers is essential to limit spread. Welfare-conscious management includes stress reduction to minimise viral reactivation from latency, appropriate vaccination, and prompt isolation of suspect cases.

What You Can Do

Vaccinate your horses against EHV-1 and EHV-4 according to your vet's recommendations
Implement biosecurity protocols when horses return from competitions or mixing with new horses
Isolate any horse showing respiratory signs and contact your vet promptly
Avoid nose-to-nose contact between horses at equestrian events and shared facilities
Stay informed about EHV outbreaks in your region through equine health surveillance networks