Veterinary Medical Teaching Hospital
College of Veterinary Medicine
Kansas State University
In the summer and fall of 2002, 15,257 horses developed encephalitis due to West Nile Virus (WNV) infection in the United States, with the Midwest being most severely affected. The first equine case in the State of Kansas was confirmed in the first week of August, 2002. Between August and November, approximately 800 WNV cases were verified in Kansas and approximately 1,400 cases in Nebraska, with confirmed cases representing all but 8 counties across those 2 states. The peak case numbers occurred during the week of September 15 in the State of Kansas. The following year, the total number of equine cases declined to 5,181 and to date in 2004, there have been 1,305 horses afflicted with WNV. Horses cannot transmit WNV to humans; the virus is transmitted to humans by mosquitoes.
Forty-eight WNV cases presented to the Kansas State University, Veterinary Medical Teaching Hospital for treatment in 2002, and the majority of those cases were unvaccinated or inappropriately vaccinated. Over 80% of hospitalized horses survived WNV encephalitis, with most cases enjoying a full recovery. The WNV vaccine has recently demonstrated 95% efficacy in an experimental setting. West Nile Virus will remain an endemic disease in the United States indefinitely with no expectation for eradication in the foreseeable future due to its persistence in the mosquito population. Appropriate vaccination and mosquito control have led to a significant decline in the total number of cases seen nationally. If you are concerned about WNV, see your local veterinarian for their recommendations about vaccination. Vaccinations and testing for WNV are available at the Veterinary Medical Teaching Hospital at Kansas State University.