Gene drives for population suppression of the malaria mosquito – where are we and what’s next?

Gene drives are a special type of genetic modification that can bias their own inheritance, allowing them to spread throughout an entire insect population within a couple of years. They can be designed to suppress the number of malaria mosquitoes by making female mosquitoes infertile. This strategy is complimentary to existing vector control, whilst having the advantage of being cheap, fast-acting and entirely self-sustaining – as it is the mosquitoes do the work of spreading the intervention. In 2015 we demonstrated the first proof-of-principle gene drive in the mosquito, however they failed to spread when released into small, caged populations because of drive-resistant mutations. By investigating how these mutations form, and what propels their spread, we were able to develop a second-generation design that can spread in small-caged testing without inducing resistance. To bridge the gap between lab and field testing, we conducted further releases in a custom-built, large-cage testing facility designed to simulate field conditions. These conditions induce complex behaviours not observed in small-scale testing such as swarming, resting and egg-laying. We observed complete population suppression in all replicates within one year of release – demonstrating the first semi-field testing of gene drive technology. These results are a crucial stepping-stone towards the use of gene drive for control of malaria in Africa.