Variation among goegraphic strains of Aedes albopictus in susceptibility to infection with chikungunya virus.

Two types of variation were observed when the susceptibility of 16 different geographic strains of Aedes albopictus to oral infection with chikungunya (CHIK) virus was studied. One was differential susceptibility to infection with the virus. The other was variation in the quantity of virus present in infected mosquitoes after a standard incubation period. Mean virus titers of infected mosquitoes of different geographic strains varied almost 1,000-fold. Attempts to develop increasingly resistant or susceptible mosquito lines through genetic selection were unsuccessful. Infection rates did not change significantly despite 3 to 6 generations of selective inbreeding. In contrast, crosses between strains of high and low CHIK susceptibility yielded hybrid mosquitoes with infection rates and mean virus titers intermediate between those of the parent colonies. These data suggest that at least one factor controlling the susceptibility of A. albopictus to CHIK infection is genetic. Two lines of A. albopictus with a marked difference in susceptibility to oral infection with dengue viruses were equally susceptible to oral infection with chikungunya virus.