FIRST HORSE IN 2009 TESTS POSITIVE FOR WEST NILE VIRUS
Submitted by: VDACS
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Date Added: 9/3/2009
The Virginia Department of Agriculture and Consumer Services (VDACS) today announced 2009’s first positive case of West Nile Virus (WNV) in a horse. The 16-year-old Tennessee Walking Horse mare was from Pittsylvania County. Onset of symptoms was August 17 and necropsy at VDACS’ Regional Animal Health Laboratory in Lynchburg took place on August 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). The mare had not been vaccinated for WNV.
Dr. Joe Garvin, 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 thought it’s late in the year. 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 such as DEET and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn.
The virus usually lives in wild birds of many different species. Mosquitoes transmit it 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 West Nile Virus and other mosquito-borne diseases.
Currently, no drugs exist to kill WNV in horses or humans. Treatment for an infected horse consists of supportive therapy 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.
WNV can cause a horse to go down and be unable to get up without help. Animal owners should consult their veterinarians if an animal exhibits any neurological symptoms such as a stumbling gait, facial paralysis, drooping or disinterest in the surroundings. Currently, there are live-animal tests for WNV in horses and chickens, but none for other animals, although testing can be done on any dead animal. Animal owners should consult their veterinarians or the nearest VDACS Regional Animal Health Laboratory for advice or information should an animal exhibit symptoms of WNV.
The following Web sites provide more information on WNV and how to protect humans and horses:
Horses:
http://www.vdacs.virginia.gov/animals/wnv.html
http://www.aphis.usda.gov/vs/nahss/equine/wnv/
Humans:
http://www.vdh.virginia.gov/epidemiology/DEE/Vectorborne/factsheets/westnilevirus.htm
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