Equine Herpes Virus Updates for Arizona, California, Georgia, Illinois, New Mexico, New York, Texas

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Winter marches on, and reports of the highly contagious Equine Herpes Virus (EHV) continue to flow in. The virus has been reported this month from coast to coast, and in boarding barns, training centers, racetracks and polo ponies. Horses have died, dozens are under quarantine, and no one is really sure where it may show up next.


Turf Paradise Park in Phoenix, Arizona lifted a quarantine this week. The restrictions centered on a group of horses that had arrived at the track from Sunland Park in New Mexico, where more than 70 horses have been diagnosed with the virus. The potentially exposed horses could have infected horses already at the Arizona track, so the gates were closed for three weeks. Horses are now allowed to come and go.


California is quietly handling its latest outbreak. A quarantine continues in Riverside County, where a polo pony was euthanized on February 7 after displaying neurologic signs. Test results showed that the type of virus on hand was the non-neuropathic form of EHV-1, and protocol required the quarantine of 70 horses on the premises. For two weeks, ending today, each of these horses had its temperature monitored twice daily, and state officials sought other horses that might have been exposed. State officials are continuing to monitor the situation, and report that there is no known link between this case and any outbreaks in other states. In January, a draft cross gelding in Los Angeles tested positive on-neuropathogenic strain of Equine Herpesvirus-1.According to the California Department of Food and Agriculture, he was treated and recovered, but his illness required all the horses on the premises where he lived to be quarantined.


On Friday, the University of Georgia College of Veterinary Medicine announced that the Large Animal Hospital at the vet school there reopened its emergency services. The clinic will resume seeing regular appointments again on February 22, according to the University website.

The hospital closed its doors to new patients on February 2 when it initiated a quarantine for equine herpesvirus. A horse had been admitted to the large animal intensive care unit on January 31 and was humanely euthanized on February 1 in response to its struggle with progressive neurological disease. On February 2, hospital officials learned that diagnostic tests confirmed the horse was positive for equine herpesvirus-1, or EHV-1. 

The horses that were in the hospital at the time were kept separate and all tested negative; they are currently being released, according to the hospital.

"The only positive case of equine herpesvirus at our facility was the original infected horse that was admitted into the hospital on January 31. This indicates that the virus was contained to that one individual horse," said Dr. Gary Baxter, associate dean for clinical services in the UGA College of Veterinary Medicine, on the university website. "I am extremely proud of how our hospital personnel responded to this incident and am thankful for the support of the equine and veterinary community. While closing a part of our facility is never ideal, we wanted to take every possible precaution to help ensure the safety of the Georgia horse population."


Sadly, an outbreak in an Illinois boarding barn claimed another horse's life this week. In the initial outbreak at the end of January, eight horses were diagnosed with the neuropathic form of EHV-2; two horses died or were euthanized, and the farm was quarantined.

The new case means that the farm's quarantine will extend for another 21 days. 

New Mexico

New Mexico is still in the throes of a serious outbreak. In less than a month, 72 horses have been diagnosed with Equine Herpes Virus (EHV-1), initiating a quarantine at Sunland Park racetrack and several local training centers, according to a report from the New Mexico Livestock Board on February 17. According to the New York Times, 12 horses in New Mexico have been euthanized since the outbreak began.

Biosecurity measures among horsemen and horsewomen are still necessary, such as taking temperatures twice a day, handwashing, washing/disinfecting anything a horse has touched or could touch, etc. 

The New Mexico Racing Commission said earlier this month that horsemen and horsewomen who failed to take and report the temperatures of their horse(s) risked being fined $250 and/or having their licenses suspended. Racetrack officials installed a compliance officer to make sure that the procedures were being done and that the results were accurate. 

New York

A single case of equine herpes virus was reported in New York state on February 16. The case was announced on the new Equine Disease Communication Center (EDCC) website. The horse is located in Chemung County, which includes the city of Elmira, about midway between Corning and Ithaca, home of Cornell University. All the horses on the farm have been quarantined.


EHV doesn't pay attention to borders. Two horses in the El Paso, Texas area have been diagnosed with EHV, making Texas the newest state to join the list of actively-affected states. The Texas Animal Health Commission (TAHC) reported that on Friday that both horses showed signs of respiratory illness, fever and nasal discharge and tested positive for EHV-1, but that neither horse showed signs of the neurologic form of the disease. The stable has been placed under movement restriction as a precaution, and all horses are being monitored daily.

Since the trainer of the sick horses trains in New Mexico, this outbreak may be related to the nearby Sunland Park situation in that state, where 72 horses have tested positive for the virus. New Mexico officials are counting the two Texas cases as part of the Sunlandoutbrea

United Kingdom

England's National Stud in Newmarket remains closed until further notice. A filly shipped in and was diagnosed with EHV while still in the isolation facility, but the finding still required the entire facility to close during the active breeding and foaling season.

This list of outbreaks illustrates the many faces of equine herpes virus, as well as the many different ways an outbreak can evolve. It may just involve a single horse for the duration of the quarantine, or it could spread to other horses before anyone even knows that a horse on the grounds is sick, let alone suffering from a contagious and potentially deadly disease.

Different states have different mandates for reporting outbreaks to the public, so don't expect to be informed. Monitor the website and Facebook page of your state animal health agency and talk to your veterinarians about what to do in the event of an outbreak, particularly if you are involved with a large population of horses living at a simple facility.