(2nd Place) Juvenile life history traits of Anopheles gambiae are altered by sub-lethal exposure to photosensitive insecticides

The control of mosquito populations and mosquito-borne diseases is a global health priority. Due to the increasing frequency with which insecticide-resistance is spreading in mosquito populations, integrated pest management strategies that incorporate larvicides and the rotation of insecticides are essential for effective mosquito control. Moreover, sub-lethal exposure to an environmental stressor, such as a larvicide, can alter the developmental trajectory of a larvae and affect mosquito life history traits that dictate vector competence. Therefore, when evaluating the efficacy of a larvicide, we must also consider how a sub-lethal exposure to that larvicide affects mosquito life history traits. Here, we investigated whether sub-lethal exposure to a promising class of larvicides, photosensitive insecticides (PSIs), affects the development and life history traits of the African malaria mosquito, Anopheles gambiae. Using sub-lethal but stressful doses of the PSIs, methylene blue (MB) and rose bengal (RB), we found that exposure altered larval development. Larvae exposed to MB pupated more quickly, and larvae exposed to RB had decreased pupal survival. Larval exposure to MB and RB did not affect the time to eclosion, adult longevity, or adult melanization potential. Altogether, PSIs alter the development of An. gambiae larvae, but the effects are limited to the juvenile life stages and do not carry-over to affect the adult mosquito. We conclude that beyond density reduction, the application of these larvicides would not have a meaningful impact on the vectorial capacity of mosquitoes.