The Texas Panhandle (26 counties) and High Plains regions (41 counties) have one of the highest West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) human neuro-incidence rates in the USA, yet surveillance for these pathogens is predominately performed through passive measures (e.g., detecting human cases at hospitals and other health clinics). There is an overall lack of active pathogen surveillance (e.g., mosquito surveillance) systems in these regions, leading to knowledge gaps in our understanding of arboviral dynamics in enzootic cycles. To address this limitation, we implemented 2 surveillance projects in 2024: localized surveillance of WNV and SLEV in the city of Lubbock, TX, and regional surveillance throughout the Panhandle and High Plains regions of the state. We used BG sentinel traps and Centers for Disease Control and Prevention light traps baited with dry ice to collect Culex mosquitoes in a multitude of habitats for both projects. All mosquitoes were identified using a dichotomous key, and then female Cx. tarsalis and Cx. quinquefasciatus were tested for WNV and SLEV as super-pools (e.g., samples containing supernatant from up to 7 individual pools that contained between 1 and 50 mosquitoes) using a combination of commercial RNA extraction kits and real-time quantitative polymerase chain reaction. In the Lubbock study, we collected 21,066 Cx. tarsalis and 15,918 Cx. quinquefasciatus, which were tested as 308 and 238 super-pools, respectively. Sixty-three Cx. tarsalis and 36 Cx. quinquefasciatus super-pools tested positive for WNV, and 8 Cx. tarsalis and 4 Cx. quinquefasciatus super-pools tested positive for SLEV. Sixteen Panhandle counties were sampled by DSHS, which collected 1,060 Cx. tarsalis and 56 Cx. quinquefasciatus. A total of 23 super-pools of Cx. tarsalis and Cx. quinquefasciatus were tested, of which only 3 (13%) Cx. tarsalis samples were found to be positive for WNV. Overall we found an abundant number of Culex spp. mosquitoes that tested positive for both viruses, which supports the Texas Panhandle and High Plains regions as high-risk regions for WNV in the United States.
Lewis et al. (Fri,) studied this question.