University of Minnesota equine specialists have been working to curb an outbreak of a highly contagious virus that can hinder brain and spinal cord function in horses.

Five of seven horses on a central Minnesota farm have shown symptoms of the potentially fatal equine herpesvirus1, which damages blood vessels in the brain and spinal cord.

One of the horses had to be euthanized and another remains hospitalized in quarantine at the Large Animal Hospital on the St. Paul campus, according to a report from the College of Veterinary Medicine. The other two returned home after showing improvement.

There were three other horses on the farm, one mildly affected and two believed to be unaffected. Their owners are monitoring them closely, the report said.

Last May, the virus hit several states in the U.S. and caused the cancellation of dozens of equine events across the nation. In that first month alone, at least 75 confirmed cases were reported in nine states, according to the U.S. Department of Agriculture.

To prevent the spread of the deadly virus strain, the University has quarantined the affected horses and refused admittance to other horses, which have instead been directed to the Piper Clinic, a separate facility within the Veterinary Medical Center on the St. Paul campus.

The contagious horses are being kept within the Large Animal Hospital in an area away from all animals and with its own air supply to prevent contamination to other animals.

The infectious disease is similar to a human strain of the herpes virus — common cold sores.

“Some of these viruses lay dormant and then sometimes with stressors they come out,” said Jeff Bender, an epidemiologist at the Veterinary Medical Center.

The virus has a few common strains, but the neurologic form is a relatively recent mutation, making preventative vaccination more difficult.

“That’s actually one of the challenges with this one: It’s pretty common out there, but this new strain seems to be causing more significant or severe disease, and unfortunately it can spread very easily.”

The disease cannot spread to humans, but it can be transported from horse-to-horse on humans’ hands or clothes, according to CVM.

It can also spread between horses from sharing equipment like bridles or water and feed buckets, or even through the air, like influenza, Bender said.

The horses are treated and kept in a special stall, which prevents physical contact and airborne particles.

Symptoms to look out for in horses with the virus include fever, weakness, incoordination and urine dribbling or inability to urinate.

“Because of the rapid progression of symptoms,” owners are encouraged to react immediately if a horse shows any of these signs, Bender said.

Bender said the virus can be active in horses for about three weeks, and they’re only contagious during that period. The initial infection was discovered in these horses roughly three weeks ago.

“Now we’re not out of the woods yet; we know these animals can potentially shed this virus anywhere from 10 to 20 days. Every day that goes by means that less virus is being shed,” Bender said. He added that the Veterinary Medical Center has had “no evidence of any further cases in the area.”

The outbreak, though contained, could highlight the fear associated with mutant viruses — in animals and in humans.

“Some of these viruses are changing,” Bender said. “They require really thoughtful and critical evaluation to help prevent the spread of that.

“There’s also a need for the equine community to know about this, and hopefully with quick intervention we’ll be able to slow the virus down.”