Horse Equine Herpesvirus Myeloencephalopathy Management

Equine herpesvirus myeloencephalopathy (EHM) is the neurological form of EHV-1 infection, causing paralysis and often requiring euthanasia, with significant biosecurity challenges.

Key Facts

EHM affects approximately 10% of horses infected with neuropathogenic strains of EHV-1
Clinical signs include sudden onset of hindlimb weakness, progressing to an inability to rise
Bladder paralysis causing urinary retention is a common and painful complication of EHM
Case fatality rate in horses that become recumbent is very high, often exceeding 50%
EHM outbreaks at competitions have led to facility-wide quarantines lasting weeks to months

Welfare Considerations

EHM causes acute and severe suffering. Affected horses experience rapidly progressing neurological dysfunction, losing the ability to walk or rise within hours to days. Bladder paralysis causes painful urine retention requiring manual catheterisation. Recumbent horses face secondary complications including pressure sores, muscle damage, and aspiration pneumonia. Early euthanasia decisions are often the most humane choice for severely affected horses. Prevention through biosecurity — temperature monitoring, isolation of horses returning from events, and movement restrictions during outbreaks — is the primary welfare strategy.

What You Can Do

Implement daily temperature monitoring for horses returning from events or mixing with new horses
Follow equine event biosecurity protocols strictly, including isolation of febrile horses
Work with a veterinarian to develop a facility biosecurity plan for EHV
Report suspected EHM cases to local animal health authorities promptly