Does prior exposure to larvicides influence dengue virus susceptibility in Aedes aegypti (Diptera: Culicidae)?

Authors: Aldridge, Robert; ALTO, BARRY - University Of Florida; CONNELLY, C. ROXANNE - Centers For Disease Control And Prevention (CDC) - United States; OKECH, BERNARD - Uniformed Services University; SIEGFRIED, BLAIR - Pennsylvania State University; EASTMOND, BRADLEY - University Of Florida; ALOMAR, ABDULLAH - University Of Florida; Linthicum, Kenneth - Ken

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2023
Publication Date: 10/3/2023
Citation: Aldridge, R.L., Alto, B.W., Connelly, C., Okech, B.A., Siegfried, B., Eastmond, B.H., Alomar, A.A., Linthicum, K. 2023. Does prior exposure to larvicides influence dengue virus susceptibility in Aedes aegypti (Diptera: Culicidae)?. Journal of Medical Entomology. 61(1):166-174. https://doi.org/10.1093/jme/tjad137.
DOI: https://doi.org/10.1093/jme/tjad137

Interpretive Summary: Mosquito populations and the diseases they cause are typically controlled by chemicals. Improper application of chemicals (i.e., under application) can have unforeseen consequences on surviving adults. These unforeseen consequences are little studied, specifically how disease transmission is impacted. This study looks at how pesticide underapplication impacts disease transmission in Aedes aegypti to dengue virus. Our results show that pesticide exposure as immatures to insect growth regulators significantly increase infection of dengue virus in Ae. aegypti adults, but not transmission. Furthermore, pesticide exposure to temephos, spinosad, and Bti did not increase disease infection of transmission of dengue in Ae. aegypti. These findings describe a previously understudied interaction between disease, mosquito, and pesticide that requires further investigation to gain a better understanding of how pesticide exposure can influence disease transmission in surviving adult mosquitoes.

Technical Abstract: Control of mosquito populations is primarily intended to reduce the transmission of pathogens they transmit. Use of chemical controls, such as larvicides, can have unforeseen consequences on adult traits if not applied properly. The consequences of under application of larvicides are little studied, specifically the impacts on pathogen infection and transmission by the vectors that survive exposure to larvicides. This study assesses the vector competence of Aedes aegypti for dengue virus, serotype 1 (DENV-1) previously exposed as larvae to an LC50 of different classes of insecticides as formulated larvicides. Our results show that larvicide exposure to insect growth regulators (methoprene and pyriproxyfen) significantly increased infection of DENV-1 in Ae. aegypti adults, but did not alter disseminated infection or transmission. Furthermore, larvicide exposure to temephos, spinosad, and Bti did not increase infection, disseminated infection, or transmission of DENV-1 in Ae. aegypti adults. Our findings describe a previously under observed phenomenon regarding the interaction of pathogen, vector, and insecticide that should be investigated to gain a clear picture of how sublethal exposure of insecticides interacts with vector development to influence vector competence for arboviruses.