P-37 - What do you do in the winter? Immature mosquito surveillance outside the “mosquito season” in Northern Virginia and its impacts on program operations.

Abstract: In the fall of 2023, we initiated year-round immature mosquito surveillance with the goal of establishing baseline mosquito data outside our routine mosquito season (early April-early November). 63 sites, primarily stormwater management facilities, were selected for sampling due to consistent larval collections during routine mosquito season operational activities. 75 “exploratory” sites were identified based on known history of winter and spring pooling and/or previous immature mosquito collections. The exploratory sites were not routinely inspected during the mosquito season. Ad hoc inspections were made in other sites (e.g., containers) as they were encountered. Inspections were typically conducted when the air temperature was > 40°F and if no accumulated snow was present at the sampling site. 1,878 site inspections were conducted from early November 2023 to early April 2024. Standing water was encountered in 1,563 (83.23%) of those inspections. Immature mosquitoes were collected in 204 (13.05%) of the inspections with water and were collected every month (November-April). Aedes canadensis, Ae. cinereus, Ae. japonicus, Ae. triseriatus, Ae. vexans, Anopheles punctipennis, Culex pipiens, Cx. restuans, and Cx. territans were collected in year-round inspections. Ae. canadensis was collected from December through early April, and was the only species collected in January and February. These initial results have already lead to operational changes within the program: Cx. pipiens and Cx. restuans collection data were used to initiate routine mosquito season inspections and control in the spring of 2024 and extend planned immature mosquito season operations later in the fall of 2024. The data collected established a baseline for year-round immature mosquito activity. Continuous monitoring can help identify changes in mosquito vector populations and seasonal activity and help our operations adapt to climate change, changes in vector dynamics, and update messaging to the public in the long term. This work will continue in the 2024-25 “off season”.