Another horse at Washington State University’s Veterinary Teaching Hospital tested positive for Equine Herpes Virus-1 (EHV-1) on Wednesday, a College of Veterinary Medicine spokesperson said, making this their fourth horse with EHV-1.
The latest case received the virus from another horse at the Veterinary Teaching Hospital, not from the horse show in Utah where the virus is believed to have originated, Charlie Powell, public information officer for the College of Veterinary Medicine, said. "This is what we call a secondary exposure," he said.
Powell said the horse had a fever during the routine checks, but nasal swabs were initially negative for EHV-1. The fever persisted, he said, and the tests came back positive Wednesday.
Professor of Veterinary Clinical Science Debra Sellon said none of the horses with the virus at the teaching hospital have shown neurological symptoms, only fevers.
"It's the horses with neurologic disease that usually have the long-term problems," she said.
The neurological progression of EHV-1 can infect a horse's spinal fluid, causing myeloencephalopathy - a severe viral brain and spinal fluid infection, Doctor of Veterinary Medicine Tanis MacDonald said on her website.
The virus cannot be transmitted to humans, dogs, cats or cattle, but is extremely contagious among horse populations, the Idaho Equine Hospital's website said.
The WSU Veterinary Teaching Hospital has released the first infected horse to its owners. The three subsequent cases remain isolated from the other horses and camelids, Powell said. The equine section of the hospital still remains under a voluntary quarantine and is not accepting or releasing any animals.
Powell said each time a new horse tests positive for the virus, the hospital extends the quarantine for 21 days.
The state of Washington has reported seven cases of EHV-1, Powell said. Three cases were reported in Whitman County, along with other single cases in each Thurston, Spokane, Chelan and Asotin counties.
Officials canceled the Lipizzaner Stallion performance scheduled on June 2, at Beasley Coliseum due to the virus cases in Pullman, Powell said.
WSU and Lipizzaner Stallions Inc. will likely reschedule the show in the future.