Jackson Hole dude ranch horses test positive for herpesvirus

JACKSON (WNE) — Two horses on a dude ranch in Teton County recently tested positive for equine herpesvirus 1.

The virus, which does not affect humans, spreads from nose-to-nose contact as well as contaminated equipment and respiratory secretions.

A veterinarian who treated the horses said the risk for transmission to horses outside the ranch is low. No cases have been reported elsewhere, he said, adding that few horses within the ranch contracted the virus.

“This is not a panic situation,” said Ernie Patterson, a veterinarian at VCA Spring Creek Animal Care Hospital. “This is isolated to one location, and not likely to spread.”

Equine herpesvirus 1 comes in four forms that can cause upper respiratory disease, infection in newborn foals, abortion or neurological symptoms. A test confirmed that the two horses on the ranch suffered from the neurological form of the virus, Patterson said.

Though equine herpesvirus vaccines exist, none are effective against the neurologic form of disease, according to the U.S. Department of Agriculture. The infected horses were vaccinated, Patterson said.

Equine herpesvirus is on Wyoming’s reportable disease list. Wyoming State Veterinarian Hallie Hasel wrote in an email that no other cases have been reported, though three other horses on the ranch have mild symptoms, Patterson said. Test results for them are expected this week, he said Tuesday.

The five sick horses are isolated from the ranch’s remaining horses, Patterson said. Other horses are under a general quarantine.

It’s unclear how the horses contracted the virus. Patterson suspects it may have come from horses the ranch leased.

This story was published on June 25, 2025.