The two men began to collaborate, and they were helped enormously by the subsequent development of CRISPR, a revolutionary gene-editing tool that made it far easier to produce the required enzymes. The Imperial team is targeting just three of the 3,500 species of mosquito – anopheles gambiae, coluzzii and arabiensis, which spread malaria in sub-Saharan Africa.
It is exploring the use of genes that will either reduce the females’ fertility, or ensure that their progeny are predominantly male (only females bite humans). Mosquitoes reproduce rapidly, so those genes could cascade through a mosquito population in a couple of dozen generations, or less than two years.
This ‘population suppression’ effectively reverses the evolutionary process, which normally favours genes that help a species survive. It would implant genes designed to do the exact opposite. ‘It’s like a genetic disease of the mosquito. It’s spreading despite the harm it’s causing to the mosquito,’ Prof Burt tells me in his office on Imperial’s Silwood Park campus, near Ascot.
Unlike conventional measures to combat malaria, it would be simple, self-sustaining and relatively cheap. It would not require a functioning health system, political stability or government funding to work. ‘It takes human frailty out of the equation, and humans are the weak point in fighting malaria,’ says Prof Crisanti in his South Kensington office.
Prof Burt’s team has already created infertile mosquitoes in the Insectary, and ones that can only breed males. It is now grappling with the problem of their evolving resistance to genetic alteration. It also has to find ways of crossing its lab mosquitoes with wild ones, and to that end has built a large lab in Terni, Italy, that mimics the climatic conditions of sub-Saharan Africa.