11/20/2025
FROM CLEMSON LIVESTOCK POULTRY HEALTH:
Subject: Multi-State Equine Herpes Outbreak
Clemson Livestock Poultry Health has been made aware of an outbreak of Equine Herpes Virus (EHV)/ Equine Herpes Myeloencephalopathy (EHM) in horses that were at or associated with barrel racing and rodeo-type events in Texas and Oklahoma. Several cases of EHM have been confirmed in Texas and Oklahoma associated with these equine events, with numerous reports of additional cases and equine deaths pending investigation.
We do not have any confirmed cases of EHV/EHM in South Carolina at this time. Our office is coordinating with the affected states and we are currently waiting to receive trace information from Texas and Oklahoma. If we receive traces from the other states, we will contact those owners directly and issue State Quarantine Orders to mitigate further spread of the disease.
This outbreak serves as a reminder of the potential disease risks associated with large commingling equine events. It underscores the importance of timely reporting of diseases and ensuring that movement requirements are followed, including veterinary inspection and health certificates prior to travel.
Horse Owners: If your horses traveled to Texas, Oklahoma, or other equine events where EHV exposure may have occurred, please contact our office directly at 803-788-2260. We will provide guidance regarding isolation and monitoring:
Exposed horses should be isolated for 21 days after last known exposure.
Appropriate isolation includes restricted access to other horses, avoiding the sharing of equipment or personnel, and utilization of protective barrier precautions.
Exposed horses should be monitored twice daily for elevated temperature (above 101.5*), respiratory signs (nasal discharge, coughing), and for clinical signs consistent with equine herpes myeloencephalopathy (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.
Upcoming equine events: Equine herpes virus can be shed for prolonged periods of time, including in clinically healthy horses, which increases risk for continued disease spread during a EHV/EHM outbreak.
Event Organizers: We recommend you consult with your veterinarian and understand the risks associated with hosting equine events during a multi-state outbreak. Cancellation or postponement of events may be important to stop continued spread of disease. If events do take place, we recommend short-timed health certificates within 72 hours and increasing biosecurity practices on site.
Horse Owners: We recommend that you consult with your veterinarian on the risks associated with travel to upcoming equine events. EHV 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 our office at 803-788-2260. 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 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. Please always check with the state of destination to ensure that you are following import restrictions.
Equine Herpes Virus Information:
EHV‐1 is spread from horse to horse through contact with nasal discharge or spread as aerosol droplets. Infected horses may not show clinical signs of the virus but may still act as carriers. Horses can also contract the virus by coming into contact with contaminated surfaces such as stalls, water, feed, tack, and transport 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. Good biosecurity practices include extensive cleaning and disinfection of surfaces and equipment that come in contact with affected horses, and individuals who treat or come into contact with infected horses need to follow appropriate disinfection protocols when handling multiple horses.
Visit the CULPH website to see the Reportable Disease List (https://www.clemson.edu/public/lph/ahp/reportable-diseases/index.html). Clemson Livestock Poultry Health can be reached at: 803-788-2260.
Additional information and resources:
A Guide to Understanding the Neurologic Form of EHV Infection
AAEP EHV FAQ
Keeping Your Horses Safe at Weekend Events
AAEP General Biosecurity Guidelines
