EQUINE WEST NILE VIRUS IN KENTUCKY: CHARACTERISTICS OF HISTORICAL TESTING AND ANALYSIS OF CAUSAL FACTORS

As the arbovirus with the highest incidence in both humans and horses in the United States, West Nile Virus (WNV) presents a significant risk to the equine population of Kentucky. Widespread infection has the potential to cause a significant economic impact to the state and long-term health complications for the horses. To better understand the burden of equine WNV, historical diagnostic testing archives the University of Kentucky Veterinary Diagnostic Lab were analyzed along with environmental and census data collected from additional sources. A total of 2146 test results were analyzed utilizing descriptive statistics, chi-square tests of independence, and binary logistic regression. Results indicated that WNV infections in Kentucky were seasonal with the majority of cases occurring in the fall months. Age and sex were statistically significant factors in overall testing characteristics. Breed testing and positivity results tended to correlate with population census data. Both testing and positive cases were found to be widespread across the state. Environmental factors of surface area of land and water by county and total horse population by county were found to have a statistically significant relationship with positive test results. As land and water surface area increased, the positivity rate increased. As total horse population by county increased, positivity rates decreased. Total rainfall by county was not found to have a statistically significant relationship with positive test results. Future research should examine equine WNV vaccine protocols in Kentucky and the purpose for testing, whether surveillance of asymptomatic horses or diagnosis of symptomatic horses.