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Equine Herpes Virus

Equine Herpes Virus Type 1 (EHV-1) infection in horses can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. The neurologic form of the disease caused by EHV-1 is called Equine Herpes Virus Myeloencephalopathy (EHM).

Transmission likely occurs by inhaling infected droplets or ingesting material contaminated by nasal discharges or aborted fetuses. Clinical symptoms may include a fever, difficulty urinating, depression, and stumbling or weakness in the hind limbs. Supportive therapy is often used to treat these cases. In severe cases, horses will be unable to stand; these cases have a very poor prognosis. EHV-1 is not transmissible to humans.

November 2025 Alert: An outbreak of Equine Herpes Virus Type 1(EHV-1) / Equine Herpes Myeloencephalopathy (EHM) was confirmed in horses that were present or associated with barrel racing and rodeo-type events in Texas and Oklahoma. Several additional cases and equine deaths are pending investigation.

Virginia does not have any confirmed cases of EHV-1/EHM in the state at this time, but the Office of the State Veterinarian is awaiting trace information from Texas and Oklahoma. The State Veterinarian will contact horse owners directly and issue State Hold Orders on any horses that are traced to locations included in the outbreak.

Horse Owners: If your horses traveled to Texas, Oklahoma, or any equine events with possible EHV-1 exposure, contact our office at 804.786.2483. We will provide detailed guidance, including:

  • Exposed horses should be isolated for 21 days after last known exposure.
  • Appropriate isolation includes restricted access to other horses, avoid sharing of equipment or personnel, and utilizing protective barrier precautions.
  • Exposed horses should be monitored twice daily for elevated temperature (above 101.5°F), respiratory signs (nasal discharge, coughing), and clinical signs consistent with EHM (neurologic symptoms including inability to stand, difficulty walking, lethargy, and urine dribbling).
  • If elevated temperature, respiratory signs, or EHM-compatible clinical signs are noticed, contact your veterinarian.

Equine Event Guidance: EHV-1 can be shed for prolonged periods of time, including in clinically healthy horses, which increases risk for continued disease spread during a EHV-1/EHM outbreak.

  • Event organizers: Consult with your veterinarian to understand the risks associated with hosting equine events during a multi-state outbreak. Event cancellation or postponement may be important to stop disease spread. Events that do take place are recommended to use short-timed health certificates within 72 hours and practice increased biosecurity on site.
  • Horse owners: Consult with your veterinarian to understand the risks associated with travel to upcoming equine events. EHV-1 is a ubiquitous virus and commonly present in the environment, so biosecurity measures are paramount to decreasing potential for disease transmission.

Veterinarians: If you have a horse with signs of acute neurologic disease, please contact the State Veterinarian’s Office at 804.786.2483. After hours, call 804.750.8845. We will provide guidance on isolation and testing. Diagnosis of EHV-1 can be difficult, as periods of viral shedding and viremia may vary - paired samples, including nasal swab and whole blood, is critical.

Interstate Movement: Please note that many states may be implementing movement restrictions or new import requirements for equines during this outbreak. Always check with the state of destination to ensure you are following import restrictions.

Information & Resources

EHM Disease Information:

Contact

For questions or more information, call:

804.786.2483

Visit the Division of Animal and Food Industry Services directory.

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