A decade of stability for wMel Wolbachia in natural Aedes aegypti populations

The wMel strain of Wolbachia blocks Aedes-borne virus transmission and can spread throughout mosquito populations by inducing cytoplasmic incompatibility. Aedes aegypti mosquitoes carrying the wMel strain of Wolbachia have been released in 'population replacement' interventions, which aim to establish wMel in mosquito populations, thereby reducing their ability to spread disease. The long-term stability of Wolbachia effects is critical for ongoing disease suppression, requiring tracking of phenotypic and genomic changes in Wolbachia infections following releases. Here we provide an assessment of the long-term stability of wMel from the very first Wolbachia population replacement release in Cairns, Australia. A comparison of wMel genomes from pre-release (2010) and up to nine years post-release (2020) populations showed few genomic differences and little divergence between release locations, consistent with a lack of change in observed phenotypes. Our data indicate that releases of Wolbachia-infected mosquitoes for population replacement are likely to be effective for many years, and should be informative for Wolbachia population replacement release programs that are taking place around the world.