Virginia Logs First Equine WNV Case for 2009

The Virginia Department of Agriculture and Consumer Services (VDACS) has confirmed and announced Virginia's first positive case of West Nile virus (WNV) in a horse for 2009. The 16-year-old Tennessee Walking Horse mare was from Pittsylvania County. Onset of clinical signs was Aug. 17 and necropsy at VDACS' Regional Animal Health Laboratory in Lynchburg took place on Aug. 21. The Division of Consolidated Laboratory Services originally tested the brain for rabies, but when that was negative, they tested for other diseases and the brain was positive for WNV by polymerase chain reaction (PCR) testing. The mare had not been vaccinated for WNV.

Joe Garvin, DVM, head of VDACS' Office of Laboratory Services, urges horse owners to check with their veterinarians about vaccinating their animals for WNV. "This is our first case of West Nile virus in a Virginia horse this year," Garvin said, "plus we have had eight equine cases of Eastern equine encephalitis (EEE), as well as cases in a goat, emu, and alpaca. Both WNV and EEE are mosquito-borne diseases, and we generally start seeing our first cases in August and September. Since both diseases are preventable by vaccination; it makes sense for horse owners to go ahead and vaccinate now even though it's late in the year. Mosquito season in Virginia can run through November."

Horse owners should consult with their veterinarians to choose a vaccination schedule to protect their horses effectively. Prevention methods besides vaccination include destroying standing water breeding sites for mosquitoes, use of insect repellents such as DEET, and removing animals from mosquito-infested areas during peak feeding times, usually dusk to dawn.

The virus can be found in wild birds of many different species. Mosquitoes transmit it from bird to bird. A mosquito that has bitten an infected bird can bite a human, horse, or other mammal and transmit the virus to them. Horses and humans are considered dead-end hosts (they cannot transmit WNV). Continuous effective mosquito control can minimize the risk of exposure of both horses and humans to WNV and other mosquito-borne diseases.

Currently, no drugs exist to specifically treat WNV in horses or humans. Treatment for an infected horse consists of supportive therapy. A veterinarian tailors treatment to the particular case.

Animal owners should consult their veterinarians if their horse exhibits any neurologic signs, such as a stumbling gait, facial paralysis or drooping, or disinterest in his surroundings. Animal owners should consult their veterinarians or the nearest VDACS Regional Animal Health Laboratory for advice or information should an animal exhibit signs of WNV.

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