INDIANAPOLIS, Ind. — Equine owners have even more reasons to vaccinate their horses this year before show season kicks into high gear. Cases of equine herpesvirus (EVH-1) have been popping up across the United States, including at a large horse show in Florida last month and a race track in Chicago late last year.

EHV-1 can cause four types of disease in horses including respiratory, abortion, neonatal death and a more dangerous neurological form known as EHM. Horses infected with EVH-1 can be carriers for many years and can appear healthy until they are stressed by strenuous exercise or long-distance transport.

Indiana does not have any known infected horses at this time, according to the Indiana State Board of Animal Health (BOAH).

“We have had cases of EHV-1 before, particularly where large numbers of horses gather,” said Sandra Norman, DVM, veterinarian with BOAH.

The last known case in Indiana was around Christmas time when a carriage company had to quarantine their horses, said Denise Derrer, BOAH public information director.

In a news release issued last week, the state agency advised horse owners to consult a veterinarian to establish a vaccination schedule as soon as possible. Also, BOAH urged bio-security measures at shows – such as preventing nose-to-nose contact between horses, cleaning hands and equipment, and not sharing buckets, hoses and other equipment among horses.

While other states have mandated additional testing for horses entering their borders, Indiana is not requiring more scrutiny at this time.

“The outbreaks have been in limited populations. It was an Illinois racetrack (that had the outbreak). It is a specific sector, not the general horse population,” Derrer told Farm World.

Complicated and serious

Caution is advised because EHV-1, while not common, is a serious threat to a horse’s health, said Carol Habig, DVM, and owner of Seven Oaks Veterinary, LLC, in Indianapolis.

“We don’t know all we need to know (about this disease). It is complicated to control and treat,” Dr. Habig said.

EHV-1 can be treated with expensive anti-viral medicines, which are not 100 percent effective, Dr. Habig said. A horse also can carry the disease for a long time before it develops symptoms. Even worse, the virus can mutate within the horse’s body into the neurologic form, which is nearly always fatal, Dr. Habig said.

“The theory is that keeping a horse regularly vaccinated reduces the instances a horse can be exposed to the herpesvirus. In turn, that may reduce seeing the disease in its neurological form,” Dr. Habig said.

There are not money-back guarantees, Dr. Norman said.

“Although vaccinating horses for equine herpesvirus can help, the vaccine is not a guarantee against infection,” Dr. Norman said.

Vaccination, to be effective, also needs to be done well in advance, at least a month prior to shows, rides or equine sporting events, Dr. Habig said.

“Horse owners need to be getting with their veterinarian now to establish a program. It takes time after vaccination for the body to mount an immune response – at least a month for any vaccine, not just the herpesvirus,” Dr. Habig said.

However, each horse’s needs are different, requiring a unique vaccination protocol, Dr. Habig added.

“That’s why we advise horse owners to work with a veterinarian to establish a vaccination protocol that includes a plan for keeping animals healthy while on the road. And, as always, biosecurity is essential to prevention,” said Dr. Norman, who favors inoculation at least five weeks ahead of potential exposure.

irus is through nose-to-nose contact between horses, BOAH stated in its release. However, the virus can also be passed indirectly through contact with contaminated objects.

Therefore, BOAH advised against sharing tack, grooming equipment, and feed and water buckets among horses. Humans cannot contract EHV-1, but handlers can spread the disease via their hands and clothing.

Show organizers should keep records of the origins of exhibition horses and their owners so that everyone can be notified in case of an outbreak, BOAH stated.

Horse owners and veterinarians need to contact the state of destination to check import requirements before shipping horses. Some states have mandated entry permits, a certificate of veterinary inspection (CVI) written within 24-72 hours, and vaccinations.

Regular updates about EHV-1 outbreaks are being posted to The Horse website, accessed through the main BOAH page, www.in.gov/boah

More information about the current situation can be found on the USDA-APHIS website at www.aphis.usda.gov/vs/nahss/equine/ehv