Ecological and genetic determinants of malaria transmitting behaviors in Anopheles arabiensis in Tanzania
Anopheles gambiae is frequently referred to as the most important vector of malaria in Africa and has been the main focus of malaria vector research. Despite this attention, there is growing evidence that it is not this species, but its sister species A. arabiensis that is increasingly responsible for malaria transmission in Africa. Reports indicate that in areas of high insecticide treated net (ITN) coverage, A. arabiensis outcompetes An. gambiae s.s and has become the dominant vector species in many locations. If this phenomenon continues as large-scale ITN programs are rolled out across Africa, this species could become the only medically relevant vector in many parts of the continent. Consequently the ecology, vectorial competence and population genetics of this somewhat neglected vector merit particular attention in preparation for future vector control scenarios.
This research program integrates vector population genomics, ecology and vector behavior with the goal of understanding the determinants of two mosquito behavioral phenotypes crucial to the transmission and control of malaria: (1) host preference and (2) adult resting behavior. Our approach builds upon a sizeable base of preliminary work, conducted in our laboratory, which has identified an extensive panel of A. arabiensis SNP markers, and preliminary field work in Tanzania that has identified a range of appropriate sites where sampling methods have been piloted and the behavior of A. arabiensis is known to vary.
A. arabiensis mosquitoes will be intensively collected from four villages in the Kilombero Valley of Tanzania during the wet and dry seasons to determine the association between their feeding and resting phenotype and environmental factors that vary temporally and spatially (component #1). DNA will be extracted from individual samples and multi-locus SNP genotypes determined from each individual. Genotypes will be organized by phenotype (exophilic vs. endophilic and human fed vs. animal fed) and analyzed to determine SNP allele associations with each phenotype after correcting for population structure (component #2).
Knowledge of the genetic basis of these behavioral changes will be vital for prediction of both possible downstream evolutionary responses to current vector control strategies, and also for the development of novel control strategies that improve the application of currently available vector control methods and/or that are based on vector genetic manipulation.
This project was conducted in collaboration with Drs. Heather Ferguson and Daniel Haydon, University of Glasgow, UK, Dr. Gerry Killeen, Ifakara Health Institute, Tanzania and Dr. Eleazar Eskin, University of California, Los Angeles.