West Nile Virus confirmed in 6 horses in Oregon; local Vet recommends vaccine
Retired Veterinarian Wally Wolf said vaccines and booster shots protect horses from West Nile Virus, which has cropped up in Oregon in recent weeks.
By Tom Peterson
Retired Veterinarian Wally Wolf of The Dalles said on Monday that the West Nile Virus was nothing to mess with when it comes to horses.
His comment comes on the recent announcement that the Oregon Department of Agriculture (ODA) received six confirmed reports of West Nile Virus (WNV) diagnosed in Oregon horses in the past two weeks.
One additional suspected case is under investigation. The affected horses live in multiple counties throughout the state: Umatilla, Malheur, and Klamath. None of the infected horses were recently vaccinated against WNV, and most of the horses have never been vaccinated for WNV.
Wolf said the WNV affects the nervous systems of horses, and it can have devastating effects.
“If a horse can’t stand up, it’s a tough job to try to get it to do that and quite often not successful,” he said. “Far as I know, the vaccine works really well. The horses we need to worry about is our rodeo cowboys and cowgirls. Their horses are up and down the road quite a bit and cover a lot of country.”
He said stopping the spread of the infection is fairly simple.
Vaccinations and annual booster shots for WNV, Western and Eastern Equine Encephalitis as well as tetanus and rabies can do the trick.
“An annual booster is recommended for those core vaccines,” he said. “It’s better to do it a little earlier in the year like May or June but now is prime time for it to crop up.”
WNV is spread by mosquitos and Wolf said a dry summer and spring likely kept their populations minimal in Wasco County.
In the Pacific Northwest, numerous additional WNV 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.
EHV-1 Diagnosis in Linn County
On September 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 (EDCC).
West Nile Virus and EHV-1 are both reportable diseases in Oregon. Veterinarians must report suspected cases to the Oregon State Veterinarian by calling 503-986-4680.
