One of the most critical factors contributing to the vectorial capacity of malaria vector mosquitoes is the mean age attained by adult females, because after picking up the Plasmodium parasite there is a lengthy incubation period before transmission can occur. A virulent strain of the endosymbiotic bacterium Wolbachia called wMelPop reduces adult lifespan in its native Drosophila host, and has recently been shown to do the same following transfer into Aedes mosquitoes. We will examine its potential as a novel malaria control tool by creating and characterizing Anopheles cell lines containing wMelPop, and purifying and transferring it into An. gambiae by microinjection. We will then characterize the cytoplasmic incompatibility phenotype by which Wolbachia spreads itself, virulence (lifespan shortening effects), maternal transmission rates, and tissue distribution of introduced Wolbachia, together with analyses of mosquito gene expression using microarrays. Development of a molecular age estimation assay for the An. gambiae complex will be undertaken by adapting a new quantitative RT-PCR method for use in An. gambiae. We will then set up a greenhouse population of a member of the An. gambiae complex in Kenya that is viable over multiple generations, release marked mosquitoes to calibrate the molecular age estimation assays under semi-field conditions, and compare age structure between greenhouse and wild populations. In Burkina Faso we will estimate population age structure in the An. gambiae complex at 3 field sites, in different seasons and with / without insecticide treated net use. Liaison will take place with government institutions and local communities on regulatory issues and desirability of future Wolbachia-based trials in both countries. We will also build a suite of mathematical models to allow the analysis of different interventions that affect adult mosquito longevity, and incorporate the dynamics of Wolbachia spread in an age-structured population.