What Is Equine Herpesvirus and Where Has It Shown Up?

Posted by TF Oren

Sunland Park, New Mexico, home of Sunland Park Racetrack, has experienced an outbreak of Equine herpesvirus 1 (EHV-1). 

The first case was discovered on Jan. 21 and veterinarians have since found another 28 infected horses, several of which, sadly, have been euthanized. Sunland Park is under a 14-day quarantine in an attempt to halt the spread of the virus.

EHV is a family of equine-specific viruses. The virus subtypes are named by numbers, and vary in symptoms and severity. Most horses carry some form of EHV, but never show symptoms. Exactly what causes clinical outbreaks is unknown, but such outbreaks are more likely to occur in areas through which many horses travel through, such as horse shows and racetracks.


Among the EHV subtypes, EHV-1, EHV-3, and EHV-4 are the most dangerous to horses. EHV-1, which can be fatal to horses of all ages, manifests in a number of ways including: neurological issues, respiratory disease, abortion, and neonatal death.

Symptoms of EHV-1 include fever, nasal and ocular discharge, swollen lymph nodes, weakness in the hindquarters, lethargy, urine dribbling, irregular gait, head tilt, and leaning against vertical surfaces to maintain balance.

EHV-1 is highly contagious. It is spread among horses primarily by nose-to-nose contact, but can also be spread to horses via contact with contaminated human hands or clothing, or contaminated objects found in the barn such as tack, cleaning rags, feed buckets, and even trailers in which infected horses have been transported. Airborne infection is also possible. EHV is strictly an equine virus, so although humans can spread EHV to horses, they cannot catch EHV from horses.


Since EHV is a virus, there is no cure. However, supportive care, including antibiotics and anti-inflammatories to treat the secondary infections that accompany the virus, can be used at the discretion of the treating veterinarian.

The horses at Sunland Park have been isolated and separated into three groups: horses with EHV-1, horses that have had contact with EHV-1 infected horses, and horses that have had no contact with either of those groups. The stalls are being cleaned regularly with disinfectants, and the local horseman's association has provided gloves, spray bottles, and bleach to everyone at the racetrack in order to encourage those in direct contact with the horses to take every possible measure to protect the horses at the racetrack and elsewhere in the community against further infection.

Interested in learning more about EHV? Check out the American Association of Equine Practitioners FAQ page.

recommended for you

What Is Equine Herpesvirus and Where Has It Shown Up?