Possible herpesvirus outbreak in Utah horses contained to 1 location, state vet says

OGDEN — Utah agriculture officials say they believe they have contained an outbreak of a serious disease in horses that was confirmed in the state earlier this month after the sick horse had attended an event in Weber County.

Dr. Dean Taylor, the state veterinarian, said equine herpesvirus myeloencephalopathy, or EHM, was confirmed in a horse in Utah on March 7. EHM is a disease from the EHV-1 virus that can be fatal or create significant complications and is spread through nasal droplets, aerosol droplets or by various shared spaces including stalls, water or transportation vehicles.

State officials didn't disclose where in the state the sick horse was reported out of respect for the horse's owner because the horse is kept at a private facility. After further investigation, they found a second horse at the property that also tested positive for EHM.

State officials said they weren't exactly sure how the originally infected horse got sick. The virus can start up internally from stress or spread horse-to-horse.

"We really don't know where this started at this point," Taylor said. "Both horses are doing well. The outbreak is confined to that one facility, and we're well beyond the two-week period that we would be concerned about there."

The first positive test drew concerns within the state's horse-owning community because it had attended events at the Golden Spike Events Center in Ogden on Feb. 20 and just before the horse's owner noticed the horse exhibiting signs of EHM.

Meanwhile, Taylor said there were also rumors floating around that a horse died from the virus spreading. He said he also started to receive phone calls on March 10 from concerned horse owners who said their horses were exhibiting signs of the virus.

As a precaution, the state had a barrel race scheduled for the Golden Spike Event Center canceled that week. The event center posted on social media on March 11 that it wouldn't hold any events until a week later as a precaution, as well, which meant more than a half-dozen events were canceled.

It allowed the state's Department of Agriculture to investigate the situation further. The department identified six facilities with possibly sick horses.

In a public letter about the situation Monday, Taylor wrote that the only premise that came back positive was the "originally positive premises." No other horses were confirmed sick with the virus, including ones that could have been exposed on Feb. 20.

"Currently this outbreak appears to be contained," the letter states. "No additional cases have surfaced from any event at the Golden Spike Event Center and we are now past the period when we would expect to have seen cases."

The letter also says the agency did not believe it was "necessary to restrict equine events going forward."

He also told KSL.com Tuesday that there was a deceased horse, but the state was unable to get any lab work done on the horse to confirm the virus nor were there any connections that would link that horse and the originally infected horse.

Taylor said the facility with the two infected horses has "done an excellent job" quarantining their horses since the original diagnosis. The facility is also close to completing a 21-day precautionary quarantine.

In addition, he commended Weber County's policy to disinfect the event center after every event because it likely factored into why the disease has only been found at one site.

"Once that horse was there on (Feb. 20), that entire facility had been disinfected prior to the next event," he said. "So that was probably, in hindsight, very beneficial in containing this disease."

As for EHM itself, it's treated with supportive care, such as providing fluids and anti-inflammatory agents. The state shared a brochure about how horse owners can handle EHV-1 and EHM following its last possible outbreak in 2019.

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