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Vector Control

Vector Control

141 - Establishing a novel age-grading method for Culex tarsalis populations using pixel intensity of wing photos.

Wednesday, March 5, 2025
2:05 PM – 2:15 PM AST
Location: 209
Abstract: A mosquito’s age is key in its ability to blood feed, lay eggs and transmit pathogens. Current methods of determining the efficacy of insecticide applications, including measuring vector abundance and index, can be insensitive due to larval density or expensive given the need for molecular analysis. These indices may also overestimate insecticide resistance or degradation of an active ingredient in areas where abundance remains high but older mosquito populations are reduced and pathogen transmission risk is decreased. As such, improved and rapid age-grading of mosquito populations could be an exceptional tool to identify changes within the population, complementing current evaluation methods, and are needed because older age-grading methods such as parity dissections are slow, qualitative and imprecise. Other new age-grading techniques can have expensive startup costs, be destructive to samples, and require advanced statistical knowledge to implement, making it impractical for most districts to perform. Therefore, we have established a simple, rapid, and inexpensive method for age-grading adult female Anopheles gambiae populations by calculating the pixel intensity (PI) of wing photos, which assesses wing scale loss over time. Over the summers of 2023-24, we used this method to age-grade Culex tarsalis populations in northern Colorado, including in 2024 to assess the efficacy of ivermectin coated birdseed to control West Nile virus transmission in a field trial. Collected Cx. tarsalis were subjected to wing removal and the wings were photographed. PI’s are currently being evaluated using an algorithm. We will use these data to analyze inferred mosquito population structure changes over time, across collection sites, and relative to control methods, as well as compare to vector abundance and index measures. We aim to make this method available to researchers and vector control districts to understand mosquito-borne disease risk and to evaluate insecticide applications in trials and during operational use.