As an associate professor and Extension equine specialist for Texas A&M AgriLife Extension, Dr. Jennifer Zoller has built her career around equine education, leadership and hands-on outreach across Texas.
Recently, there have been concerns about equine herpesvirus (EHV) after an outbreak linked to an equine event in Texas resulted in horses exhibiting clinical neurological signs of EHV. The virus can cause respiratory disease, reproductive issues and neurologic disease in horses.
EHV is widely present in horse populations, Zoller said, and outbreaks can occur at some points because it is so transmissible.
“The concern is that EHV can occasionally lead to a neurologic form of the disease, which is the outbreak that we are hearing about right now, equine herpesvirus myeloencephalopathy (EHM),” Zoller told WLJ.
The outbreak stems from the Women’s Professional Rodeo Association (WPRA) World Finals and Elite Barrel Race held in Waco, TX, from Nov. 5-9. The Texas Department of Agriculture (TDA) issued an alert on Nov. 19 urging all WPRA event attendees or attendees from any recent large equine gathering in the area to monitor their animals and implement heightened biosecurity measures.
“While investigations are ongoing, the TDA believes the situation warrants immediate attention, given the rapid spread and severe outcomes in affected horses,” the department said in a news release.
EHV is transmitted by touch, Zoller said. “Direct horse-to-horse contacts, aerosolized droplets from coughing or snorting, indirect contact from contaminated surfaces like stalls, trailers, tack, sharing water buckets, things like that,” she said. “Those horses left that event and went back to their home bases. Some of those were out of state, and that’s what the concern is, the transmission of the disease.”
Horses are able to shed the virus during the incubation period, which ranges from two to 10 days, even before showing clinical signs. It is recommended to quarantine any horse coming back from an event for at least 14 days to be able to monitor for symptoms.
Any time there is an event, there can be outbreaks, Zoller explained. The most critical thing that horse owners can do is practice good biosecurity. “This is not something new to the horse industry,” she said.
On Nov. 18, the San Antonio Stock Show & Rodeo made the decision to cancel the Uvalde Rodeo Qualifier scheduled for Nov. 19-22 because of the outbreak. Just one day later, the Boot Barn Prairie Circuit Finals Rodeo to be held in Mulvane, KS, from Nov. 19-22 was canceled. The Cowtown Coliseum in Fort Worth, TX, also made the decision to postpone all equine events through early December. The 2025 National Finals Breakaway Roping was postponed to Dec. 22-23 in the Cowtown Coliseum.
A current list of the canceled or postponed WPRA divisional circuit jackpots can be found at wpra.com.
The Wrangler National Finals Rodeo (NFR) was set to continue as scheduled but will require updated health and biosecurity protocols. All horses must have a seven-day certificate of veterinary inspection and a unique entry permit number from the Nevada Department of Agriculture, and competitors must conduct daily temperature checks on their horses. There is also a no-travel advisory for all horses participating and competing in the NFR, and there will be enhanced verification and check-in procedures.
While event and horse facilities managers have protocols for biosecurity, Zoller recommends horse owners also follow their own strict biosecurity measures, ensuring horses are set up for the best-case scenario in the event of travel or competition.
“This is an emerging situation,” she said. “So, things can change on a daily basis. The best thing we can do is monitor what’s happening, make sure you’re relying on reputable sources for your information and talk to your local veterinarian.”
For up-to-date, reputable information, Zoller recommends following the Equine Disease Communication Center (EDCC), American Association of Equine Practitioners and local Extension specialists.
EHV symptoms
EHV most often presents respiratory system symptoms. This includes runny nose, fever, coughing, lethargy and enlarged lymph nodes. EHV can also cause abortion in mares. Neurologic signs of EHM include hind limb weakness, incoordination, loss of tail tone, urine dribbling, leaning against walls, and, in severe cases, recumbency. While fever often occurs before neurologic symptoms, lack of fever does not rule out infection.
Most horses are exposed to EHV early in life and may carry the virus in a resting state, which can reactivate during stress events such as travel, illness or competition. EHM occurs when an EHV infection causes inflammation and damage to blood vessels in the brain and spinal cord. While only a small percentage of horses with EHV develop EHM, the condition can be fatal.
“The neurologic form of the disease can be a little bit scarier because of the symptoms those horses present,” Zoller said. “But the neurologic form of the disease is less common. And most horses will recover from it with supportive care from the veterinarian.” The recovery rate for horses with EHM is about 60-80% when it is caught and treated quickly, she added.
The EDCC is monitoring the EHM outbreak linked to the WPRA Waco event. As of Dec. 1, six states had officially confirmed EHM cases: Texas (18 cases), Oklahoma (seven cases), Louisiana (three cases), South Dakota (one case), Colorado (one case) and New Mexico (three cases).
In Texas, the neurologic form of EHV is a reportable disease and can be reported at tahc.texas.gov. “It’s important that if there is a suspected case, the horse owner or caretaker, the veterinarian or the lab where the test is run, reports it so that the EDCC and Texas Animal Health Commission can keep track of this particular outbreak,” Zoller said.
While there is not necessarily a cure for EHV, Zoller recommends horse owners contact their veterinarian for supportive care and quarantine practices based on the outbreak in their area.
“There is some conversation out there about vaccine availability and how that might impact horses that are traveling,” she noted. “But work with your local veterinarian for any of those questions.”
Biosecurity measures
Texas A&M AgriLife Extension recommends the follow biosecurity measures:
• Isolate horses returning from travel for at least 14-21 days, monitoring them twice a day for fever.
• Avoid nose-to-nose contact and sharing of tack and grooming tools, and disinfect all equipment.
• Clean trailers and stalls of manure, bedding and water before disinfection.
• Limit personnel contact with multiple horses, wear designated clothing when handling exposed animals, and wash hands thoroughly after contact.
• Work with a veterinarian for a vaccine protocol based on individual horse needs.
• Maintain accurate records of horse movements and exposure history. — Anna Miller Fortozo, WLJ managing editor
