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Contact: Sally J. Baker or (859) 233-1047

Although fall is underway, the American Association of Equine Practitioners urges horse owners to vaccinate or booster their animals against West Nile virus (WNV).

The Equine Disease Communication Center (EDCC) reports 152 cases of WNV thus far in 2018, with almost all diagnosed during the months of August and September. Most confirmed cases occurred in horses which were unvaccinated or had an unknown vaccination history.

In geographic areas with continued warm weather and mosquito activity, horse owners are encouraged to talk to their equine veterinarian today about WNV protection.

“For unvaccinated horses, it is critical to start the multiple-dose vaccine series to prevent infection, even this late in the season,” said Dr. Linda Mittel, AAEP Infectious Disease Committee member. An incomplete series will not protect horses.”

For horses boostered against WNV this past spring and now traveling to or stabled in areas where there is current mosquito activity and a history of WNV, an additional booster may be needed.

Also, horses considered to be high risk, such as juvenile horses (less than 5 years of age) and geriatric horses (more than 15 years of age), may require more frequent vaccination depending on risk assessment. Vaccination for West Nile virus is recommended as a core vaccine by the AAEP and is an essential standard of care for all horses in North America.

Since first being recognized in the United States in 1999, WNV has posed a serious threat to horses and humans alike. Virus transmission occurs in the horse when a mosquito takes a blood meal from a bird infected with WNV, then feeds on a horse.

WNV can be fatal. While many horses exposed to WNV experience no signs of illness, the virus can cause inflammation of the brain and spinal cord. The case fatality rate for horses exhibiting clinical signs of WNV infection is approximately 33%. Data have supported that 40% of horses that survive the acute illness caused by WNV may exhibit residual effects, such as gait and behavioral abnormalities, six months post-diagnosis.

Review the AAEP’s vaccination guidelines for WNV here and the EDCC fact sheet here.

The American Association of Equine Practitioners, headquartered in Lexington, Ky., was founded in 1954 as a non-profit organization dedicated to the health and welfare of the horse. Currently, AAEP reaches more than 5 million horse owners through its over 9,000 members worldwide and is actively involved in ethics issues, practice management, research and continuing education in the equine veterinary profession and horse industry.


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