Project Summary The goal of this project is to understand how populations of the important disease vector Aedes aegypti are responding to rapid urbanization in sub-Saharan Africa. The proposed work is designed to 1) test in the field whether host-seeking females in the rapidly growing cities of Ouagadougou, Burkina Faso and Kumasi, Ghana show greater attraction to human hosts than host-seeking females in nearby rural areas and 2) to identify the specific genes driving this behavioral shift. The proposed work builds on my recently published finding that laboratory colonies of Ae. aegypti established from dense urban areas were more attracted to human hosts than laboratory colonies established from nearby rural areas in sub-Saharan Africa; these behavioral shifts were associated with genetic differences in a few key chromosomal regions. Modeling based on United Nations projections of urban growth suggested that these effects will increase dramatically in the next 30 years. I will use paired mosquito traps baited with human and non-human animal odors to test preference for human hosts across urban-rural gradients in Ouagadougou and Kumasi, building on productive and pre- existing collaborations. In a parallel analysis using a molecular barcoding approach, I will separate blood-fed individuals into sets that chose human or non-human animal hosts, and determine whether differences in host preference translate into differences in rates of feeding on human hosts. Using low-coverage whole genome sequencing of mosquitoes from both of these collections, I will simultaneously identify genomic shifts across this urban-rural gradient and identify specific genes involved in driving individual differences in host preference. This work will clarify the causes and evolutionary mechanisms underlying rapid changes in vector populations, and provide key tools for monitoring and preventing the emergence and spread of mosquito-borne disease in high-risk regions.