According to a West Umatilla Mosquito Control District press release today, West Nile virus has been detected in a horse north of Hermiston. Testing at the Oregon State University Veterinary Diagnostic Lab in Corvallis, Oregon confirmed the results Friday. According to the press release, this is the first detection in a horse in Umatilla County since 2009. The positive horse comes five weeks after officials first detected the virus in mosquitoes in Umatilla County.
Horses, like people, acquire the infection from mosquitoes that have fed off infected birds. The most important preventive measures that horse owners can take is to eliminate mosquito breeding areas around the farm which are found where stagnant water collects. They should also consider vaccinating their horses for West Nile Virus, Emilio DeBess, public health veterinarian said in the press release. The vaccine is available from veterinarians and it is necessary to complete the full course of vaccination to achieve effective immunity. This includes at least two doses 3-6 weeks apart and then one dose annually thereafter. The use of insect repellents and screening may also be helpful.
Horses infected with the virus will show neurological signs consistent with infection of the brain and spinal cord, similar to encephalitis in humans. The most frequent signs include: weakness; lack of coordination affecting mostly the hind limbs, which may include falling down and an inability to rise; depression or apprehension, and muscle tremors."