Hot Blooded: What to Know About the Racetrack EHV-1 Outbreaks

EHV-1 has been the buzz lately in the equine world and not for a good reason. With recent outbreaks at Keeneland and Turfway Park in Kentucky and the Fair Grounds Race Course in Louisiana, it is clear that the virus is a growing problem of which every horse owner should be aware. Here are some basic things you need to know to keep your horses safe and your risk level low.

First, you might ask, “What is EHV1?”

By definition, according to the UC Davis School of Veterinary Medicine, “EHV-1 (equine herpesvirus-1) is one of a large group of DNA viruses causing potentially serious disease in horses and other species. EHV-1 has two forms: one that causes abortion in mares and one that causes respiratory infection and neurological symptoms.”

A recent outbreak of the virus’s neurologic strain at the New Orleans racetrack has been particularly controversial after a barn occupied by five trainers and their strings of Thoroughbreds were quarantined. A majority of the horses showed no symptoms of EHV-1, but tested positive after veterinarians collected nasal swabs. The entire backside of the Fair Grounds Race Course has been quarantined and no horses can be transported in or shipped out. Among the notable mounts being affected: the 2016 Kentucky Derby third-place finisher, Gun Runner, whose $12 million Pegasus World Cup entry this weekend was canceled after he was not cleared for transport in time.

The outbreak has also been the cause of headaches for horse owners in Northern Kentucky, where five known cases of EHV-1 have been reported in Oldham County. Two of these cases also tested positive for the neurologic form of the disease. “We are on high alert in this area of Kentucky as there are several surrounding barns that adopt and repurpose ex-race horses for new careers such as eventing and dressage,” says Dr. Adrienne Robertson whose practice, Bannon Woods Veterinary Clinic, is located in Louisville, just 19 miles from the outbreak.

What are the symptoms?

Respiratory symptoms of EHV-1 may include a fever of 102°F or greater, nasal discharge, swelling of the lymph nodes and the area around the throatlatch. Neurologic symptoms, when present, will peak within 24 to 48 hours after their initial onset. These may include lethargy, urine dribbling, head tilt,  incoordination or loss of balance (especially in the hind end), or inability to rise. Symptoms for EHV-1 may appear similar to those of influenza.

What’s the best way to protect my horse (and farm) against potentially sick animals? 

One thing to remember about biosecurity is that practicing it every day will greatly decrease the chances of illness during outbreaks. (For more information, check out “Biosecurity for Horse Owners” by Alicia Skelding of Equine Guelph.)

Here are a few helpful tips:

  • Any new horses to the property should be checked by a vet before arrival and observed while isolated from the resident horses for at least 30 days.
  • Vermin control (rodents, birds, and insects) is critical as they can carry disease in and out of your barn.
  • Avoid sharing buckets, feed tubs, grooming supplies, equipment, etc. from horse to horse in your barn.
  • Do not use one water source for multiple horses.
  • Know your horse’s normal vitals: temperature, heart rate, and respiratory rate; learn what is normal for your horse and what isn’t.
  • Wash your hands! Not only will it keep you from getting sick, but it will also help your horse avoid illnesses as well.
  • Establish a specific plan with your vet in case there is a contagious outbreak on your property. It’s better to be prepared than to be blindsided.

What about EHV-1 vaccines?

In addition to increasing the overall biosecurity at your farm, Dr. Robertson is recommending vaccination for EHV-1. “Our practice is recommending that horses with increased risk be vaccinated at this time. Currently, there is not a vaccine labeled for the neurologic form of Herpes, however, the available respiratory vaccination is known to be of value in limiting the spread of outbreaks of the neurologic form by limiting nasal shedding and dissemination of infection.”

Your best bet? Talk to your own veterinarian to see which of the options available are best for you and your horse.

-Photo credit: Furlongs.


  1.  “Equine Herpevirus,” UC Davis Veterinary Medicine Center for Equine Health
  2. “What are the symptoms of EHV-1 and how do I protect my horse?” Hagyard Equine Medical Institute
  3. “FAQ: Regarding Equine Herpevirus (EHV)” American Association of Equine Practitioners
  4. “10 Biosecurity Tips from Top Equine Health Experts” The Horse

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