112 - Ready, Set, Action Thresholds in Williamson County, Texas

Abstract: Action thresholds for adult mosquito control in response to detection of West Nile virus (WNV), are created specifically for each jurisdiction. Factors that influence these thresholds include public health risk and public acceptance to adult mosquito control methods. Historically, the Integrated Vector Management (IVM) Program at Williamson County and Cities Health District (WCCHD) has managed responses to WNV detection on a case-by-case basis with treatment decisions determined by affected municipalities. As more guidance and data have become available, the IVM Program has created data-driven action thresholds that can be shared with partner cities to guide in decision making related to adult control. Mosquito and human WNV data from 2018-2021 were analyzed to create and evaluate action thresholds for adult mosquito control in response to WNV detection. Trap abundance, trap positivity, and infection rates were calculated during each WNV detection in mosquito samples and compared at a “regional” versus county-wide level. A table was created to supplement WCCHD’s Phased Response Guidelines for WNV with action thresholds and control recommendations based on the risk presented at the time of WNV detection. Action thresholds will be evaluated annually and adjusted as needed.