ALBUQUERQUE, N.M. – The New Mexico Department of Agriculture (NMDA) and the New Mexico Livestock Board (NMLB) are urging horse owners to take immediate preventive measures following confirmation of the state's first case of equine herpes myeloencephalopathy (EHM), the neurologic disease associated with Equine Herpesvirus-1 (EHV-1).
The affected horse, located in Doña Ana County, attended the 2025 Women's Professional Rodeo Association World Finals and Elite Barrel Race in Waco, Texas, held Nov. 5-9. The animal is currently isolated from other horses and is improving with supportive veterinary care.
This confirmation comes as the Texas Animal Health Commission and the Oklahoma Department of Agriculture, Food, and Forestry announced confirmed EHM cases in their respective states on Nov. 18, following equine events attended by horses from multiple states, including New Mexico.
EHV-1 is a common, highly contagious virus that affects horses, donkeys and mules. It spreads through respiratory secretions, shared equipment, trailers and contaminated environments. While it cannot infect humans, the virus can cause respiratory illness, abortions, foal death and the serious neurologic condition EHM in horses. Symptoms may include fever, nasal discharge, cough, lethargy, hindlimb weakness, difficulty rising, loss of tail tone, urinary retention and—in severe cases—inability to stand.
"Immediate isolation and veterinary evaluation are the most effective tools we have," said state veterinarian Dr. Samantha Holeck. "Horse owners should closely monitor their animals and practice heightened biosecurity, especially if they recently attended events in Texas or Oklahoma."
Veterinarians diagnose EHV-1 through PCR testing of nasal swabs and whole blood, which provides the most accurate results. State officials emphasize that early testing and strict isolation of any horse showing signs of illness are critical to preventing further spread.
Although there is no cure, most respiratory cases recover fully with supportive care, and mares affected by the reproductive form typically improve. Neurologic cases vary widely, with severe paralysis carrying a poorer prognosis.
To reduce risk, state officials recommend that horse owners:
Follow veterinary vaccination guidance
Isolate new horses for 2-3 weeks before introducing them to the herd
Avoid sharing equipment such as halters, buckets and grooming tools
Disinfect barns and tack regularly
Monitor horse temperatures daily during high-risk periods
Limit horse movement during regional or local outbreaks
Additional resources are available from the New Mexico Livestock Board, the New Mexico Department of Agriculture, the American Association of Equine Practitioners and the U.S. Department of Agriculture's Animal and Plant Health Inspection Service.
For questions about EHV-1 testing, contact NMDA's Veterinary Diagnostic Services at 505-383-9299. For regulatory or livestock health concerns, contact the New Mexico Livestock Board at 505-841-6161. Horse owners should consult their veterinarians for guidance on diagnosis, treatment and vaccination.
