Eradicating Malaria

"With this achievement, the major barriers to saving lives are arguably no longer mostly technical, but social and diplomatic."
"The known harm of malaria greatly outweighs every possible ecological side-effect that has been posited to date, even if all of them occurred at once."
Kevin Esvelt, study, evolution of gene drives, Massachusetts Institute of Technology

"We are not saying this is one hundred percent resistance-proof. But it looks very promising."
"This is the first time we’ve shown that we can, in principle, manipulate the fate of an entire species."
Andrea Crisanti, biologist, Imperial College, London

Andrew Hammond

Among the world's worst disease scourges, caused by a parasite and transmitted by mosquitoes, in 2016 alone malaria infected 194 million people across Africa, causing 445,000 of that number to die an early death. Now comes news that biologists have succeeded in developing a manipulation of mosquito genetics forcing entire mosquito populations to self-destruct by making them incapable of reproducing. Laboratory research testing the technique has been so successful the researchers have determined that through their methodology malaria could be eliminated within 15 years, freeing large areas of Africa from their presence.

A research team, led by Andrea Crisanti disrupted the mosquito's sexual development by altering a gene rendering the females infertile while the males still capable of spreading the gene only produce a dwindling number of offspring, as a result. Through research, the team realized  their laboratory mosquito populations could be driven to extinction within the space of 11 generations. This signal finding was reported in Nature Biotechnology last month, spreading the news that wild populations of mosquitoes could be manipulated out of existence in four years, if computer models are to be believed.

In a study published last year, Andrea Crisanti, right, and his colleagues were able to spread an infertility mutation to 75 percent of a mosquito population. (Mike Kemp / Bill & Melinda Gates Foundation)

For the scenario to unfold it is dependent on the technique pioneered by these researchers to equip mosquitoes with a gene drive which is a genetic mechanism to force a gene into all of an organism's offspring. Gene drives can occur naturally without human intervention, but sexual reproduction passes genes to only half the progeny; installing a specific gene drive in an effort to alter genes interfering with reproductive capacity, all the progeny, not just a portion of them are affected.

This gene drive function has the capability of carrying forward a gene rapidly, producing a powerful and potentially dangerous effect. Dangerous in that successfully installing a gene drive in the wild would be an irreversible event; should it happen that such an advent triggers a like reaction in other creatures, it could result in another species being doomed to extinction. In the past, efforts to reduce mosquito fertility with the use of gene drives failed, since mutations arise in stretches of DNA scientists target and what results is the nullifying of the engineered alterations.

Engineering the gene --

(Graphic by Charles Floyd; Research by Molly Ginty)

However bypassing the possibility of mutations favoured by natural selection allowing the mosquito to escape from the trap was achieved by Dr. Crisanti and his colleagues when they discovered how to target a stretch of DNA that is unvarying from one mosquito to another. They found this DNA sequence in a gene named doublesex, specializing in determining sexual development, in one of the major carriers of the malaria parasite, Anopheles gambiae.

With the concern uppermost in mind of the potential risk in launching a gene drive into the wild which, once released cannot be recalled, cannot be contained within national borders or easily disabled, the researchers proceeded with caution. The U.S. National Academy of Sciences made it mandatory in 2015 for tests and public consultation to take place before the release of any gene drive.

And now, biologist Austin Burt of Imperial College, London, part of the research team, anticipates a field trial to be initiated in five years' time in Africa. "We wouldn't have to hit every village, maybe as few as one percent", he offered in the initial implementation where a few hundred drive-carrying mosquitoes would be released in each of the chosen villages.

The malaria parasite cannot maintain its populations once its numbers fall below a certain level, so total eradication is not an absolute requirement, before the species crashes.