A horse barn in Washington County has been placed under a precautionary quarantine because of a case of equine herpesvirus Type 1.

Minnesota Board of Animal Health officials say the horse, a 16-year-old mare, tested positive last month for the highly infectious virus, which can develop into a debilitating neurological disease known as equine herpesvirus myeloencephalopathy (EHM).

Because the horse exhibited symptoms consistent with EHM, the Board of Animal Health has issued a quarantine for the remaining 60 horses on the property to control the spread of the virus. All of the quarantined horses will be monitored daily for fever and other signs of illness.

The horse’s owner, who was not identified, first noticed clinical symptoms on April 22 and “voluntarily instituted biosecurity measures to reduce the risk of potential spread, such as limiting visitors to the farm and isolating the affected horse and those considered to be higher risk exposures,” according to a news release issued by the board.

A veterinarian examined the horse the next day and noted “significant balance and muscle control issues and dribbling urine,” the news release states.

The horse has shown marked improvement in the last 48 hours, officials said Tuesday.

State officials shared a number of tips for owners to follow when traveling with horses. Among them: Clean and disinfect tack, boots, equipment and grooming supplies before returning home, and don’t let your horse touch other horses, especially nose to nose. Workers also should wash their hands before handling horses and shouldn’t share water or feed between horses.

“EHM is highly contagious, and horse owners should take their biosecurity seriously to avoid it,” Heather Damico, senior veterinarian in charge of equine programs at the Board of Animal Health, said in a statement. “Thankfully, we have a plan in place to control the spread of the disease when it does pop up.”

The last case of EHM diagnosed in Minnesota was in June 2024. Multiple cases continue to be identified throughout the United States, the release states.