218 - Should routine surveillance traps be placed in problem spots or in a uniform grid?

Abstract: St. Tammany Parish Mosquito Abatement District (STPMAD) uses data from mosquito traps as point locations to inform where zone-based treatments will occur. Historically, trap locations have been chosen to maximize collections of Culex quinquefasciatus, the primary vector of West Nile virus locally. Placement at these problem spots allows for comparison of the worst sites across STPMAD’s jurisdiction but is not necessarily indicative of problems elsewhere or for other vectors. Recently STPMAD has begun creating geospatial surface models of mosquito abundance using this habitat-biased routine surveillance trap network. Traps in urban areas are often within close proximity of one-another, especially compared with traps in more rural areas. As a result, habitat-biased trap sites may not be the best fit for modeling mosquitoes across an area due to their erratic placement and inherent bias toward particular species. In 2024 STPMAD began evaluating two surveillance networks simultaneously: 1) habitat-biased traps (targeting Cx. quinquefasciatus), and 2) traps placed approximately within the center of squares of an equidistant grid covering the district. A third set of randomly located validation traps tested the performance of the two trap placement cohorts, and all sets were deployed on the same night. Three replicates were performed in a 210 km² area within the district during different weeks of the season. Initial results indicate few differences between trapping regimens in terms of species diversity or raw abundance. However, predictive modeling power increased with more uniform distribution of traps placed in the gridded regimen. This distinction is relevant to the residents of the district which live in between trap sites or in areas with low trap density, as population modeling may shed light on additional places in need of treatment in the future.