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West Nile Virus in a virus causing encephalitis, with many similar clinical signs to rabies, eastern and western encephalitis, wobblers disease and equine protozoal myelitis (EPM). Some of the early signs noted are incoordination, weakness, uncontrolled muscle twitches, inability to stand and death. Infected horses may or may not have an elevated temperature. West Nile virus is harbored in wild birds and may be spread to humans and horses by mosquitoes. At this time, there is no effective way to prevent the disease from developing in your horse other than vaccination. There are several different types of vaccination available for protection against West Nile disease: - Fort Dodge’s West Nile-InnovatorTM for horses is indicated for the vaccination of healthy horses as an aid in the prevention of viremia caused by West Nile Virus. MetaStim™, the technologicallyadvanced adjuvant, is exclusive to Fort Dodge equine vaccines.
- Intervet’s PreveNileTM contains a lyophilized Yellow Fever West Nile (YF-WN) chimera virus vaccine. The human vaccine yellow fever virus, YF-17D, was used as the backbone. The YF-17D strain is a highly effective, well-tolerated live, attenuated vaccine that has been used for over 60 years to immunize approximately 400 million people1. The YF-17D virus was modified using molecular technology to form a YF-WN chimera virus that expresses the PreMembrane and Envelope proteins of WNV. Following injection, limited replication of the YF-WN chimera virus allows expression of these proteins that stimulate a protective immune response in the horse.
- Merial’s RECOMBITEK® Equine West Nile Virus contains a lyophilized recombinant canarypox vectored West Nile Virus vaccine plus a sterile liquid diluent. A canarypox vector has been modified using recombinant technology to express the desired antigens capable of stimulating a protective immune response to West Nile Virus. After inoculation, the vector does not multiply in the horse, but does express the protective proteins. As a consequence, these components induce an immune status against West Nile Virus. Safety and immunogenicity of this vaccine have been demonstrated by vaccination and challenge tests in susceptible horses.
Regardless of the product used, I recommend vaccinating horses in endemic areas once yearly, in the spring before the mosquito season. 10 Tips for Reducing Your Horse’s West Nile Risk Since first being recognized in the United States in 1999, West Nile virus (WNV) has poseda serious threat to horses and humans alike. In the equine population, the virus is transmitted when a mosquito takes a blood meal from a bird infected with WNV, then feeds on a horse. While many horses exposed to WNV experience no signs of illness, the virus can cause inflammation of the brain and spinal cord. In some cases, especially in older horses, WNV can be fatal. As a horse owner, prevention is the key to reducing your horse’s risk of contracting WNV. Follow these guidelines from the American Association of Equine Practitioners (AAEP) to protect your horse against WNV: 1. Consider vaccinating your horse against the disease. In February 2003, a vaccine was licensed by the United States Department of Agriculture’s Center for Veterinary Biologics for use in healthy horses as an aid in the prevention of the disease. Talk with your veterinarian about the most appropriate vaccination schedule for your horse. 2. Eliminate potential mosquito breeding sites. Dispose of old receptacles, tires and containers and eliminate areas of standing water. 3. Thoroughly clean livestock watering troughs at least monthly. 4. Use larvicides to control mosquito populations when it is not possible to eliminate particular breeding sites. Such action should only be taken, however, in consultation with your local mosquito control authority. 5. Keep your horse indoors during the peak mosquito activity periods of dusk to dawn. 6. Screen stalls if possible or at least install fans over your horse to help deter mosquitoes. 7. Avoid turning on lights inside the stable during the evening or overnight. 8. Using insect repellants on your horse that are designed to repel mosquitoes can help reduce the chance of being bitten. 9. Remove any birds, including chickens, located in or close to a stable. 10. Don’t forget to protect yourself as well. When outdoors in the evening, wear clothing that covers your skin and apply plenty of mosquito repellent. For more information about the virus, ask your equine veterinarian for the “West Nile Virus” brochure, produced by the AAEP in conjunction with Bayer Animal Health, an AAEP Educational Partner. Additional information about WNV can be found on the AAEP’s horse-health Web site, www.myHorseMatters.com Reprinted with permission from the American Association of Equine Practitioners.
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