Four Oregon horses have now tested positive for Equine herpesvirus-1 (EHV-1), with two of the horses showing neurologic clinical signs, the Oregon Department of Agriculture (ODA) reported May 4.

Last week the department announced that a Marion County horse had tested positive for EHV-1 and had developed neurologic signs. The second horse that developed neurologic signs resided at a stable in Polk County with about 40 other horses and was taken to Oregon State University’s College of Veterinary Medicine Large Animal Hospital over the weekend. The Polk County stable has been placed under quarantine and the remaining horses are being monitored by the stable manager and a veterinarian.

In addition to the Polk County stable, two Marion County farms remain under quarantine due to EHV-1 exposure. The infected horses and other horses exposed at the quarantined facilities attended an Oregon high school equestrian team meet at the Linn County Fairgrounds on April 16-19.

The ODA is currently investigating the potential of any additional exposures, is working to notify owners of horses that could have been exposed, and has notified Oregon equine veterinarians