We now have a weapon that could wipe out one of the world’s biggest killers

One bite at a time.
One bite at a time.
Image: Shutterstock/mycteria
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The deadliest organism on the planet rides in mosquito bellies and kills more than 400,000 people every year. Though we’ve cut malaria deaths by half since 2000, there is a long way to go. The fight is so great that there have been demands to obliterate mosquitoes, and the malaria-causing parasite with them.

But eradication is no easy task. Just consider the fight against polio, which began in 1988 and still costs hundreds of millions of dollars every year.

Now a new weapon, called “gene drive,” offers a cheap and easy way out. It allows scientists to hijack the process of evolution and pass on genes at incredible speeds. In a study published in the Proceedings of National Academy of Sciences, scientists at the University of California at San Diego and Irvine have developed the first prototype of a gene drive for mosquitoes that makes them immune to the parasite.

Normally, an organism born through sexual reproduction has a 50-50 chance of inheriting any given gene from either of its parents. So if a mosquito has a gene that makes it immune to carrying the malarial parasite, only some of its offspring will inherit the immunity. But certain genes in nature have developed a mechanism for creating multiple copies of themselves, thus increasing their chances of being inherited.

The scientists’ technique is to add this copying ability to a gene for immunity to malaria, and implant mosquitoes with that modified gene. In theory, if some of these genetically engineered mosquitoes are released in the wild, within months they will create a population of mosquitoes that cannot carry malaria. Wait a few years, and it is thought that all mosquitoes on the planet could be made immune.

In their experiment, the California researchers inserted the gene drive into 680 embryos of Anopheles stephensi mosquitoes, the main carrier of malaria in Asia. The drive had two genes that produced antibodies against the malaria parasite, Plasmodium falciparum; one gene that changed the mosquitoes’ eye color (so that they could be monitored); and the copying mechanism. When they mated these genetically modified mosquitoes with wild ones in the lab, they found that, even by the third generation of mosquitoes, 99% had inherited the modified gene. Without gene drive, only 50% would have.

This is just proof-of-concept. Researchers still need to check that the gene drives works in wild breeds of mosquitoes, not just lab-grown ones, for instance. More importantly, before it can be deployed, they will have to convince the public, and regulators, that gene drives are safe to use.