Application of wMelPop Wolbachia Strain to Crash Local Populations of Aedes aegypti

The endosymbiotic bacteria Wolbachia pipientis ( w Mel strain) has been successfully established in several populations of Aedes aegypti , the primary dengue vector. The virulent Wolbachia strain w MelPop is known to cause several pathological impacts (increased egg mortality, life shortening, etc.) reducing overall fitness in the mosquito Ae . aegypti . Increased egg mortality could substantially reduce egg banks in areas with a lengthy monsoonal dry season, and be employed to eliminate local populations. We tested this application under semi-field cage conditions. First, we determined that w MelPop infection significantly reduced the survival of desiccation-resistant eggs of the dengue vector Ae . aegypti , with shade and temperature having a significant impact; nearly all w MelPop-infected eggs failed to hatch after 6 and 10 weeks in summer and winter conditions, respectively. In laboratory selection experiments we found that egg desiccation resistance can be increased by selection, and that this effect of w MelPop infection is due to the nuclear background of the host rather than Wolbachia . We then conducted an invasion of w MelPop within a semi-field cage using sustained weekly releases of w MelPop infected mosquitoes, with fixation achieved after 9 weeks. The egg populations w MelPop infected and an uninfected control were then subjected to a simulated prolonged monsoonal dry season (2.5 months) before flooding to induce hatching. The w MelPop infected eggs suffered significantly greater mortality than the controls, with only 0.67% and 4.35% of respective infected and uninfected eggs held in 99% shade hatching after 80 days. These studies suggest that w MelPop could be used to locally eliminate populations of Ae . aegypti that are exposed to prolonged dry conditions, particularly if combined with vector control.