Equine Herpes virus outbreak could impact U.S. horse show schedules


SALEM, Ohio — An outbreak of the Equine Herpes Virus at the National Cutting Horse Association Western National Championship April 29-May 8 in Ogden, Utah, impacting shows and competitions across the United States.


The Equine Herpes Virus causes respiratory disease, abortion in mares, neonatal foal death and neurologic disease.

The neurologic form of equine herpes virus is called Equine Herpes Virus Myeloencephalopathy.

Both forms of the virus have been identified in horses that attended the Utah competition. So far, according to a report issued May 19 by the National Cutting Horse Association, 33 cases have been confirmed. Of those, 32 cases are in horses at the event.

Unfortunately, seven horses associated with this incidence are dead or have been euthanized.


According to the Texas Animal Health Commission, the virus is very contagious and spreads easily from one horse to another. Because EHV-1 is a virus, it does not respond to antibiotics.

Therefore, supportive treatment is the only option and is guided by the severity and range of clinical signs. It usually includes anti-inflammatory drugs, fluids to maintain hydration, and slinging of horses that are unable to stand.

In most cases, horses that remain standing have a good prognosis, although recovery make take weeks or months. Horses that do go down and are unable to stand have a poor prognosis.

The cases have been reported in eight states, including California, Colorado, Idaho, New Mexico, Oregon, Texas, Utah and Washington.

According to the Texas Animal Health Commission , the virus is spread primarily through coughing or sneezing, but can also be carried in fetal tissues, the placenta and uterine fluids from mares that have aborted. Studies have shown that the virus doesn’t live long in the environment, but transmission via coughing or sneezing can occur over a distance of up to 35 feet.

No cases locally

So far, no cases have been recorded in Ohio, West Virginia or Pennsylvania, and no events have been canceled because of the outbreak. However, the worry continues that the disease may have already been passed along unknowingly.

Horse owners must be vigilant of the possibility that exposed horses may still be incubating the disease.

Show changes

It is recommended that horse owners consider the risk of participating in upcoming events and/or co-mingling their horses with other horses and equipment (trailers) of unknown history.

The incubation period is usually about between four and six days.

Some other states have established emergency rules for entry as a result of this situation, so if interstate travel is planned, owners and/or veterinarians writing health certificates should check in advance to ensure they meet all entry requirements.


It is recommended that all newly purchased horses or introduced horses to a premise should be isolated to help prevent the accidental introduction of EHV-1 (and other diseases) onto the premise, if they have been in the western portion of the United States.

Equine Herpes Virus

— The virus routinely causes upper respiratory infection in young horses (weaning, yearlings, and 2 year olds) resulting in depression, a snotty nose, loss of appetite, and a persistent cough.

— Pregnant mares that become infected often abort their foals late in gestation, deliver stillborn foals or weak foals that die within days of birth.

— In rare instances, adult horses experience the respiratory form of the virus and then develop the neurological form of the disease.

— Horses infected with the neurologic strain of the Equine Herpes Virus might have a fever as well as nasal discharge, uncoordination, hind end weakness, recumbency, lethargy, urine dribbling and diminished tail tone.

(Source: Texas Animal Health Commission and Kansas State University Vet School)


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