Phenotypic segregation of Aedes aegypti for immune antibacterial activity and resistance to filariae.

We report the phenotypic selection of two lines of Aedes aegypti, from a filariae susceptible parental stock (Refm). This selection was based upon the level of inducible anti-gram negative Escherichia coli activity within the haemolymph following E. coli infection. These lines, denoted 'high' and 'low', demonstrated significant differences in anti-E. coli responses throughout. However no difference was observed in the anti-gram positive Micrococcus luteus response following E. coli challenge. F4, F6 and F9 mosquitoes were experimentally infected with Brugia pahangi microfilariae. Reductions of between 53 and 82% in the mean number of larvae completing development in the 'high' compared with the 'low' responding line were observed. Corresponding reductions of between 30 and 50% in the mosquito infection rates also occurred between these lines. These reductions were significant for trials on the F6 and F9 generations. We have therefore selected for Ae. aegypti possessing significant refractoriness to filaria infection. Importantly, this 'high' line has not been exposed to selection pressure using filariae development as a phenotypic selective marker.