Infectious diseases: A two-pronged attack on mosquitoes

Near-elimination of an invasive, disease-carrying mosquito species is demonstrated in a field trial in China. The environmentally friendly and cost-effective approach, described in Nature this week, combines sterilization of females along with the introduction of an infection in males to control mosquito populations.

The globally invasive mosquito Aedes albopictus is responsible for transmitting viruses such as dengue, Chikungunya and Zika. Supressing the population of this species using traditional approaches has proven challenging. A method of insect population control that uses radiation to sterilize males before releasing them into the wild has had limited success in mosquitoes, as it reduces the reproductive competitiveness of released males relative to wild populations. An alternative approach involves infecting males with a symbiotic bacterium called Wolbachia, which causes an incompatibility when mating with females that do not have the same strain of Wolbachia. However, there is a risk that with this technique females infected with the same strain might be released accidentally and come to replace the local population, preventing future population suppression that relies on this Wolbachia strain.

Zhiyong Xi and colleagues infected mosquitoes with a novel combination of three Wolbachia strains (unlikely to occur in wild populations), then irradiated them to sterilize any accidentally released females with the same Wolbachia profile - but at radiation levels that do not impair male reproductive competitiveness. In a field trial in Guangzhou, China, the release of millions of the triple-infected, irradiated mosquitoes led to near-elimination of wild mosquito populations over a two-year period. The average numbers of wild-type mosquitoes were reduced yearly by around 83% to 94%, with none detected for up to six weeks after release. Population genetics analyses indicate that the few remaining mosquitoes were probably migrants from outside the study area.