Variation among geographic strains of Aedes albopictus in susceptibility to infection with dengue viruses.

The comparative susceptibility to dengue virus infection of 13 geographic strains of Aedes albopictus was studied by feeding the mosquitoes on a virus-erythrocyte-sugar suspension. Significant variation in susceptibility for each of the four dengue serotypes was observed among the geographic strains. Mosquito strains which were more susceptible to infection with one dengue serotype also were more susceptible to the other dengue serotypes. There was a direct relationship between the amount of virus ingested and the infection rate in a given mosquito strain. A 100-fold difference in oral ID50 was noted between the most and the least susceptible strains. Crossing experiments between susceptible and resistant mosquito strains produced hybrid progeny with intermediate susceptibility. Susceptibility to infection by dengue 2 virus was decreased by selective inbreeding in one strain from 74% to 13% in two generations. Further selection, however, failed to produce a completely resistant line. It appeared that the actual "barrier" to infection was in the mosquito midgut.