INDIANAPOLIS – More than two weeks after they were potentially exposed to equine herpesvirus type 1 (EHV-1), about 30 horses in Indiana were showing no signs of developing the contagious disease, according to the Indiana State Board of Animal Health (BOAH).

The horses had participated in events in Waco, Texas, and Guthrie, Okla., in November. BOAH issued a health advisory after horses from those states that had attended either event tested positive for EHV-1. In the Hoosier state, the owners of horses listed on the event rosters were contacted and asked to adhere to a self-imposed quarantine for 14 to 21 days beginning Nov. 18, BOAH said.

EHV-1 is common in the horse population and most often clinically manifests as just a mild respiratory illness, especially in young horses, known commonly as equine rhinopneumonitis, the agency said. Less commonly, EHV-1 manifests itself as a neurological form known as EHM, or EHV-1 myeloencephalopathy, BOAH said. Symptoms of EHV-1 include decreased coordination, fever, hind limb weakness, lethargy and the inability to get off the ground.

EHM can progress to recumbency and death in severe cases, said Dr. Heather Solomon-Gabl, BOAH’s equine health director.

“Survivors may have residual neurologic deficits for weeks to months,” she told Farm World. “(Another) concern is the ease of transmission. The most common route of exposure is via the respiratory route such as inhalation of droplets from coughing and snorting or direct contact with respiratory tract secretions. EHV-1 may also cause abortion, and direct contact with aborted fetuses, fetal membranes and/or fluids serves as a source of contagion.

“Virus-contaminated fomites are the cause of indirect transmission. Fomites are objects that carry the virus and potentiate viral spread. Examples include clothing, footwear, grooming equipment, tack, water and feed sources, and the surfaces of stalls and wash racks.”

As of Dec. 3, there were no confirmed cases of EHV-1 in the state, Solomon-Gabl said. The incubation period is typically four-seven days, though it can vary with clinical signs appearing as early as 24 hours or as late as 14 days, she added. Horse owners were asked to contact their local veterinarians for testing should clinical signs develop.

When a veterinarian receives a positive laboratory result for EHV-1 on a horse showing neurologic signs, the veterinarian will contract BOAH. The BOAH district veterinarian will help manage the situation to lessen spread of the disease, the agency said.

Good biosecurity when traveling and interacting with other horses at equine events and boarding facilities is important, Solomon-Gabl said.

“Wash hands frequently and avoid sharing tack and other equipment unless it has been properly cleaned and disinfected,” she said. “Vaccination is important but unfortunately, there are no licensed vaccine products labeled to prevent or control EHM. From a regular standpoint, EHV-1 outbreaks during the autumn and winter are not surprising. In Indiana, BOAH expects to see at least one case per year.”

As the 14-day self-imposed quarantine period ended, Solomon-Gabl said there was less concern for new cases over the following seven days.

“It is important for owners to recognize the risk for contagious disease at any event. Good biosecurity and vigilant monitoring for abnormalities are paramount to keeping our horses healthy.”

For more information, visit www.in.gov/boah/species-information/equinehorses/.