The Oregon Department of Agriculture has released an urgent announcement regarding 5 confirmed reports of West Nile Virus (WNV) that have been diagnosed in horses across Oregon– all within the past couple of weeks. The report also detailed multiple horses with confirmed or suspected exposure to Neurotrophic EHV-1 (Equine Herpesvirus Myeloencephalopathy-EHM). Two of the affected horses with EHV-1 have been euthanized.
The Oregon State Veterinarian released the alert on the evening of September 9th, following a report from a veterinarian in Linn County of EHV-1 being diagnosed in two horses on a private farm. There is a third suspected case on the same farm, with two additional exposed horses.
The Oregon State Veterinarian statement said, “The preliminary epidemiological investigation indicates that there has not been movement onto or off of the farm in the past 4 weeks, and there are no known exposures at this time. The farm has been placed under quarantine.”
“While there are no known exposures, the Oregon State Veterinarian recommends horse owners who are concerned about exposure to EHV-1 monitor their horse’s rectal temperature twice daily 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 EDCC and the American Association of Equine Practitioners”
The cases of Equine West Nile Virus have occurred in multiple clusters throughout the state with cases reported in Umatilla County, Malheur County, and Klamath County. None of the cases were currently vaccinated against WNV, with most of the cases never having been vaccinated for WNV.
Numerous additional WNV cases have also been reported recently in Washington, Idaho, and California near the Oregon border.
West Nile Virus remains an important disease of horses with cases seen each year. Annual vaccination has been shown to be an effective tool at preventing WNV infection in horses. More information and guidance for equestrians is available the American Association of Equine Practitioners
West Nile virus and Equine Herpesevirus Neurologic Syndrome are both immediately reportable disease in Oregon. Suspected and confirmed cases must be reported to the Oregon State Veterinarian by calling 503-986-4760.