Abstract
The endosymbiotic bacterium Wolbachia is being developed as a tool to suppress mosquito populations and their transmitted pathogens, with successful field trials in multiple countries having resulted in efforts to scale up the capacity to mass-produce mosquitoes for release. However, major challenges exist to achieving this goal, including concerns that mass-reared mosquitoes will adapt to laboratory conditions during long-term maintenance and experience inbreeding depression, resulting in poor performance of the released mosquitoes in the field. Here, we assessed the performance of the Aedes albopictus HC line infected with a triple-strain Wolbachia after mass-rearing at scaled-up densities of up to 15 million mosquitoes per week for over 50 generations. In comparison with the wild-type GUA line, the HC mosquitoes had desirable characteristics for mass-rearing and release, including robust male mating competitiveness, high female reproductive capacity, reduced vector competence for dengue virus, and increased Wolbachia density. Although the larval survival rate of the HC and GUA lines was similar, the HC larvae developed significantly faster, possibly because of up-regulation of the molting hormone 20-hydroxyecdysone-related gene E75 in the HC larvae. Our results indicate that over many generations mass-reared mosquito lines can retain their quality if large effective population sizes with sufficient genetic heterogeneity are maintained under optimized rearing conditions and demonstrate the long-term feasibility of deploying Wolbachia-based approaches for area-wide management of mosquito vectors for disease control.
Highlights
Pathogens transmitted by mosquitoes, including malaria parasites, and dengue and Zika viruses, cause severe mortality and morbidity globally, but traditional vector control approaches are insufficient to protect humans from infection
In contrast to the breeding and release of insects for screwworm and medfly control programs, there is a potential risk of arbovirus transmission among those involved in—or associated with—the mass-rearing or massrelease of mosquitoes, either through escape of adult females within the rearing facility itself, or immediately following male release, if any contaminant females remain as a consequence of imperfect sex separation
The early detection of reductions in fitness and other quality parameters of mass-reared mosquitoes resulting from laboratory adaptation and/or inbreeding depression are essential for the success of vector control programs involving mass-release of artificially bred insects
Summary
Pathogens transmitted by mosquitoes, including malaria parasites, and dengue and Zika viruses, cause severe mortality and morbidity globally, but traditional vector control approaches are insufficient to protect humans from infection. The early detection of reductions in fitness and other quality parameters of mass-reared mosquitoes resulting from laboratory adaptation and/or inbreeding depression are essential for the success of vector control programs involving mass-release of artificially bred insects. Except for a minor reduction in female longevity, we found that HC mosquitoes otherwise retain key biological traits upon prolonged mass-rearing, including male mating competitiveness, Wolbachia-mediated virus blocking, and other life-history traits. These findings support the long-term feasibility of deploying IIT for area-wide management of mosquito vectors for disease control
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