Equine Herpesvirus: Managing Neurological Disease and Respiratory Welfare

Equine herpesvirus (EHV) causes respiratory disease, abortion storms, and potentially fatal neurological disease in horses. Understanding biosecurity and welfare management reduces suffering during outbreaks.

Key Facts

Equine herpesviruses EHV-1 and EHV-4 are the clinically most significant; EHV-1 causes respiratory disease, abortion, and equine herpesvirus myeloencephalopathy (EHM).
EHM (neurological EHV-1) is the most serious clinical manifestation: spinal cord vasculitis causes hindlimb paresis or paralysis, bladder dysfunction, and recumbency.
A neuropathogenic strain of EHV-1 (characterised by the D752 mutation) is associated with higher rates of EHM but non-neuropathogenic strains can also cause neurological disease.
The case fatality rate of EHM ranges from 30-50% in severely affected horses; survivors may have lasting neurological deficits.
Horses that become recumbent and cannot rise have a poor prognosis; welfare decisions about euthanasia must be made rapidly.
EHV-1 spreads rapidly in competition environments through nasal secretions, fomites, and direct contact; outbreaks have shut down major equestrian events.
Current vaccines provide protection against respiratory disease and abortion but inconsistent protection against EHM.
Biosecurity during outbreaks requires strict quarantine, temperature monitoring of all horses on affected premises, and suspension of horse movements.

Welfare Considerations

Horses with EHM suffer significant and rapidly progressing neurological impairment. Hindlimb weakness advancing to paralysis is frightening for a prey animal accustomed to flight as its primary defence. Bladder dysfunction causes pain and risk of cystitis. Recumbent horses rapidly develop pressure sores and secondary complications. The decision about whether to attempt intensive supportive care (slings, assisted urination, anti-inflammatory therapy) versus euthanasia requires rapid clinical assessment and must prioritise the horse's welfare rather than owner attachment. Respiratory EHV-1 is less severe but still causes significant malaise and discomfort. Abortion from EHV-1 represents a welfare harm primarily to the mare through the physical and presumably emotional disruption of pregnancy loss; foals born prematurely from EHV-1-induced abortion rarely survive without intensive care.

What You Can Do

Vaccinate horses against EHV-1 and EHV-4 every 6 months — vaccination reduces the severity of respiratory disease and abortion risk.
Monitor horse temperatures twice daily during outbreaks and isolate any horse with a temperature above 38.5°C immediately.
Report suspected EHV neurological signs (ataxia, hindlimb weakness, bladder dysfunction) to your vet as an emergency.
Implement strict biosecurity when attending competitions or events with horses from multiple premises.
Follow your national equine disease authority guidance on movement restrictions during EHV outbreaks.