Horse owners need to practice good biosecurity if their animals will come in contact with other horses at events such as horse shows, rodeos and county fairs. (NDSU photo)The virus is highly contagious and can cause respiratory or neurologic infections, abortions in mares and even death.

Cases of the equine herpes virus (EHV) have been confirmed in horses in North Dakota and surrounding states this spring.

EHV-1, also called rhinopneuomonitis or rhino, is a highly contagious viral equine disease that can cause respiratory or neurologic infection, abortion in mares and even death. It can be spread by airborne droplets, as well as contaminated tack, feed and other items.

The virus generally survives up to seven days in the environment, but it can remain alive for up to a month in perfect environmental conditions.

The recent cases are a reminder for horse owners to practice good biosecurity if their animals will come in contact with other horses, such as at horse shows, rodeos and county fairs, North Dakota State University animal experts say.

Biosecurity is a set of preventive measures designed to reduce the risks of introducing and transmitting an infectious disease agent. Horses, people, equipment, other domestic animals, vehicles, insects, feed, waste and water all can carry and spread infectious disease pathogens.

“Horse owners and event managers are responsible for implementing an equine biosecurity plan to protect the equine industry,” says Leigh Ann Skurupey, animal science specialist in NDSU Extension’s Center for 4-H Youth Development.

“If you go to events, have your horses current on all vaccinations, have current health papers, and take all your own tack and equipment,” NDSU Extension veterinarian and livestock stewardship specialist Gerald Stokka advises. “Do not share equipment with others or ask to use theirs.”

Owners should consult with their regular veterinarian to determine the proper vaccinations for their animals.

Carrie Hammer, NDSU associate professor of equine science, recommends that anyone with a horse that was at an event where EHV-1 has been confirmed should keep that horse away from other horses for at least 21 days.

The EHV-1 virus has an incubation period from one to 20 days. Horses can shed the virus during the incubation period without showing any clinical signs.

Hammer encourages horse owners to visit the AAEP’s website on EHV-1 ( to learn how to protect their horses.

“Humans cannot contract the virus, but they can spread the virus on their clothing, boots and hands,” she says.

Once a horse becomes infected with EHV-1, it is infected for life. An estimated 70 percent of the U.S. horse population has been exposed to the virus. After the initial clinical signs, the virus lies dormant and resurfaces during times of stress, such as weaning, trailering, training or competition.

Clinical signs for the EHV-1 respiratory disease are a nasal and eye discharge, fever and depression. The respiratory form of the disease is by far the most common. Symptoms for the neurologic disease include staggering, stumbling, head tilting or behavior changes.

Contacting a veterinarian quickly is important for getting the right diagnosis and treatment, according to Stokka.

“A high rectal temperature (102 F or greater) is often the very first sign, so taking daily temperatures of at-risk horses can be beneficial in detecting the disease early,” he says.

A variety of vaccines are available for protection against EHV-1. However, while the vaccines reduce the risk of infection and the severity of clinical signs for respiratory infection, they do very little to prevent the neurologic form.

The protection from the vaccine is very short-lived; therefore, horses at high risk (those traveling and exposed to multiple horses frequently) should be vaccinated every six months. Pregnant mares should be vaccinated with an approved (killed virus) vaccine at the fifth, seventh and ninth month of gestation.

Stokka notes that vaccines for EHV-1 are designed to prevent respiratory disease and abortion from EHV-1; no vaccine is available to protection against neurologic disease.

“The bottom line is that EHV-1 is very common and horse owners should do their part to minimize the risk of infection,” Hammer says.

Source: North Dakota State University extension