2 serious horse viruses confirmed in Oregon, including Malheur County

The Oregon Department of Agriculture has confirmed West Nile virus cases in horses in multiple counties throughout the state, including Malheur. According to a news release, none of the infected horses were recently vaccinated against West Nile virus, and most of the horses have never been vaccinated for the virus.

MALHEUR COUNTY — The Oregon Department of Agriculture received six confirmed reports of West Nile virus diagnosed in Oregon horses in the past two weeks, according to a news release on Sept. 13. One additional suspected case is under investigation. The affected horses live in multiple counties throughout the state, including Malheur, Umatilla and Klamath. None of the infected horses were recently vaccinated against West Nile virus, and most of the horses have never been vaccinated for the virus.

Numerous additional West Nile virus cases have also been reported recently in Washington, Idaho, and California near the Oregon border. Therefore, ODA advises annual vaccination as an effective tool for preventing WNV infection in horses.

Please refer to the Equine Disease Communication Center’s website for more information on reportable equine diseases and West Nile Virus.

On Sept. 9, 2021, Oregon State Veterinarian, Dr. Ryan Scholz, DVM, received a report that Equine Herpesvirus Myeloencephalopathy (EHV-1) was diagnosed in one horse and suspected in a second horse on a private farm in Linn County. A third horse on the same farm tested positive for EHV-1, with a fourth and fifth horse exposed. Two of the affected horses were euthanized. A preliminary investigation shows none of the five horses have been moved off the farm or in contact with other horses in the past four weeks. As a result, Dr. Scholz placed the farm under quarantine.

EHV-1 is highly contagious. While there are no known exposures linked to the Linn County farm, Dr. Scholz recommends that horse owners concerned about exposure monitor their horse’s temperature and contact their veterinarian if a fever or clinical signs develop. EHV-1 testing is generally not advised in asymptomatic horses. More information is available from Equine Disease Communication Center.

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