11/21/2025
Information directly from WI DATCP
Multi-State Equine Herpes Outbreak
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has been notified an outbreak of Equine Herpes Virus (EHV)/Equine Herpes Myeloencephalopathy (EHM) in horses that attended barrel racing and rodeo events in Texas and Oklahoma in November. Several cases of EHM have been confirmed in Texas and Oklahoma, with reports of additional cases and equine deaths pending investigation.
DATCP is monitoring this situation closely. Currently, there are no reported cases of EHV/EHM in Wisconsin. The last reported case in Wisconsin was in April 2025. Texas and Oklahoma are still working to notify states of participants in these events. DATCP will follow-up with any participants from Wisconsin to mitigate further spread of the disease.
Horse Owners: If your horses traveled to Texas, Oklahoma, or other equine events where EHV exposure may have occurred, please contact our office directly: (608) 590-5997. We will provide instructions regarding isolation and monitoring.
Exposed horses should be isolated for 21 days after last known exposure.
Isolation includes preventing access to other horses and avoiding the sharing of equipment or personnel between exposed and non-exposed groups.
Exposed horses should have a re**al temperature recorded twice daily.
Clinical signs that should be reported to your veterinarian include: elevated temperature (above 101.5º), respiratory signs (nasal discharge, coughing), or clinical signs consistent with EHM (neurologic symptoms including inability to stand, difficulty walking, lethargy, and urine dribbling).
Upcoming Equine Events: Equine herpes virus can be spread by horses that are not showing any clinical signs, which increases risk for disease transmission during an EHV/EHM outbreak.
Event Organizers: Consult with your event veterinarian and understand the risks associated with hosting equine events during a multi-state outbreak. Cancelling or postponing events may be necessary to stop the spread of disease. DATCP’s website has information on creating a biosecurity plan for equine events.
Horse Owners: DATCP recommends consulting with your veterinarian on the risks associated with travel to equine events. Vaccinations are available for EHV-1 & EHV-4 which can help prevent respiratory and reproductive symptoms. There are no vaccines labeled for the prevention of the neurologic form of EHV-1 and vaccines should not be used on exposed horses. However, vaccinated horses may assist in limiting the spread of outbreaks of EHM by limiting viral shedding.
Veterinarians: If you have a horse with signs of acute neurologic disease, please contact our office at (608) 590-5997. We will provide guidance on isolation and testing. Diagnosis of EHV can be difficult as periods of viral shedding and viremia may vary - paired samples, including nasal swabs and whole blood (EDTA) is recommended. For more information about testing, contact Wisconsin Veterinary Diagnostic Laboratory.
Interstate Movement: Please note that many states may be implementing movement restrictions or new import requirements for equines during this outbreak. Please check with the state of destination to ensure that you are following import restrictions.
Equine Herpes Virus: EHV‐1 is spread from horse to horse through contact with nasal discharge or spread as aerosolized droplets. Infected horses may not show clinical signs of the virus but may still spread disease. Horses can also contract the virus by coming into contact with contaminated surfaces such as stalls, water, feed, tack, and vehicles. People can spread the virus from horse to horse by contaminated hands and clothing. It is important for owners to watch for signs and symptoms and practice biosecurity measures.
This outbreak serves as a reminder of the potential disease risks associated with commingling animals at large events. DATCP recommends consulting with your veterinarian on the risks associated with travel to upcoming equine events. Good biosecurity can help limit the spread of this disease. There is risk of disease transmission anytime animals are commingled. If your horses traveled to Texas, Oklahoma, or other equine events where EHV exposure may have occurred, it is critical that you isolate your horses and do not travel to equine premises or events for at least 21 days.
Additional information and resources:
Equine Herpesvirus | Equine Disease Communication Center
Equine Herpesvirus Resources | AAEP
DATCP Home Equine Herpesvirus
DATCP Home Basic Biosecurity
DATCP Home Biosecurity Resources for Events
