Indoor resting behavior of Aedes aegypti and Culex spp. (Diptera: Culicidae) in northeastern Thailand

Abstract Background: Aedes aegypti is a vector of several arboviruses, notably dengue virus (DENV), which causes dengue fever and more severe forms such as hemorrhagic fever. Vector control is currently the main method to control dengue outbreaks. Effective vector control strategies require an understanding of aspects of the bioecology of the vector, including resting behavior. The aims of this study were to investigate the resting behavior of Ae. aegypti in selected houses in northeastern Thailand. Methods: Mosquitoes were collected in 60 houses in each of two rural and two urban sites in northeastern Thailand. Household characteristics were ascertained. Mosquitoes were collected from May to August 2019 during two collection times (morning/afternoon), in four room types (bedroom, bathroom, living room and kitchen) in each house and at three wall heights (<0.75m, 0.75-1.5m, >1.5m) using a battery-driven aspirator and sticky traps. Collected mosquitoes were identified and dengue virus detected in Ae. aegypti. Association analyses between location, household variables, geckos and mosquito abundances were performed. Results: A total of 2,874 mosquitoes were collected by aspirators and 1,830 by sticky traps. Aedes aegypti and Culexspp. accounted for 44.8% and 53.2% of the specimens, respectively. Only 2.1% were Ae. albopictus. Ae. aegypti and Culex spp. rested most abundantly at intermediate and low heights in bedrooms and bathrooms. Clothes hanging at intermediate heights were associated with higher numbers of Ae. aegypti in rural settings. The absence of eaves, low wind flow and hanging clothes were associated with more Culex spp. in urban settings. Infrequent use of fogging or larval control was associated with high numbers of Culex spp. and Ae. aegypti. Overall, there seemed to be no clear relationships between sticky-trap collected geckos and Ae. aegypti or Culex spp. abundances. Conclusions: Knowledge of indoor resting behavior of adult mosquitoes and associated environmental factors can guide the choice of the most appropriate and effective vector control method. Our work suggests that vector control using Targeted Indoor Residual Spraying focusing on walls at heights lower than 1.5 m in bedrooms and bathrooms could be part of an integrated effective strategy for dengue vector control.