The Virginia Department of Agriculture and Consumer Services (VDACS) announced the state’s first positive case of West Nile Virus (WNV) in a horse in 2015. The horse, a five-year-old Choctaw mare, is from Orange County. The horse was not currently vaccinated for WNV.
The onset of WNV symptoms started August 3, 2015. The horse was treated at an equine veterinary hospital in Charlottesville and discharged when its symptoms improved.
Dr. Joe Garvin, head of VDACS’ Office of Laboratory Services, urges horse owners to check with their veterinarians about vaccinating their animals for WNV. “WNV is a mosquito-borne disease,” he said, “and we generally start seeing our first cases in August and September. The disease is preventable by vaccination, as is Eastern Equine Encephalitis, so many veterinarians recommend vaccination at least yearly, and in mosquito-prone areas, every six months.” He adds that mosquito season in Virginia can run through November.
The WNV vaccine for equines initially requires two doses administered three to six weeks apart. The vaccine takes four to six weeks from the second dose for optimal effectiveness. Horse owners should consult with their veterinarians to choose a re-vaccination schedule to protect their horses effectively. Prevention methods besides vaccination include destroying standing water breeding sites for mosquitoes, use of insect repellents and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn.
Mosquitoes can transmit the virus from bird to bird. Occasionally a mosquito that has bitten an infected bird will then bite a human, horse or other mammal and transmit the virus to them. Transmission between horses and humans is extremely unlikely. Continuous, effective mosquito control can minimize the risk of exposure of both horses and humans to mosquito-borne diseases.
Currently, no drugs exist to treat WNV specifically in horses or humans. The mortality rate in equines with WNV is about 30 percent. Since there is no specific treatment for WNV, treatment consists of supportive therapy to maintain the animal’s hydration, and to prevent the animal from injuring itself throughout the two to three weeks of the disease. A veterinarian can prescribe treatment tailored to the particular case.
Animal owners should consult their veterinarians if an animal exhibits any neurological symptoms such as a stumbling gait, going down, facial paralysis, drooping or disinterest in their surroundings.