How An Altered Strand Of DNA Can Cause Malaria-Spreading Mosquitoes To Self-Destruct

For the first time, scientists have shown that a new kind of genetic engineering can crash populations of malaria-spreading mosquitoes.

Transcript

SARAH MCCAMMON, HOST:

For the first time, scientists have used a new kind of genetic engineering to decimate a dangerous species living in conditions that mimic its natural habitat. Researchers hope the advance will help conquer one of the world's biggest health problems, malaria. But critics say this technology is too dangerous. NPR health correspondent Rob Stein has the story.

ROB STEIN, BYLINE: This new kind of genetic engineering is called a gene drive. And it can do something that scientists have always tried to prevent from happening. It makes a genetic modification spread really fast through an entire species. That's been taboo to keep genetic engineering from running amuck. But a gene drive makes a gene disobey the natural laws of genetics. It's inherited by virtually every offspring. Ruth Muller is a German scientist experimenting with gene drives.

RUTH MULLER: Normally, you'll have a 50-50 percent from the mother and the father from the genes in children. And if you have a gene drive, this is not actually true. So you can distribute your genomic material to all of the offspring.

STEIN: Scientists use the gene editing technique called CRISPR to create gene drive male mosquitoes that could mate with natural female mosquitoes that spread the malaria parasite in Africa. All the females would be born with a mutation in a gene known as the double-sex gene.

MULLER: It deforms the females so they cannot bite any more on blood. So the mouth part is deformed.

STEIN: If they can't bite, they can't spread malaria.

MULLER: They are also not fertile anymore. So they don't produce offspring.

STEIN: Because their reproductive organs are deformed, too. So they can't lay eggs. And the species would quickly just die out. But this is really controversial because of fears that something could go wrong. So the researchers built a special, high-security lab in Italy designed to keep their gene-drive mosquitoes from escaping, and far from Africa in case, somehow, any did manage to get out. They released the gene-drive mosquitoes into special large cages containing hundreds of natural mosquitoes. The cages mimic the environment in sub-Saharan Africa, temperature, humidity, even sunrise and sunset. Their research is supported by the Bill and Melinda Gates Foundation, which also supports NPR. And today, the researchers are reporting that it worked. The gene drive decimated the natural mosquito populations in less than a year.

MULLER: Our study is the first who could show that gene-drive technology works under ecologically challenging conditions. So this is the big breakthrough that we made with our study.

STEIN: Muller says this is a crucial step towards hopefully someday releasing the mosquitoes into the wild in Africa to try to prevent hundreds of millions of cases of malaria and save hundreds of thousands of lives every year. But critics say these mosquitoes are just too dangerous.

NNIMMO BASSEY: The idea of gene-drive mosquitoes is something that is very disturbing to me and to many of the people I speak to.

STEIN: Nnimmo Bassey heads the Health of Mother Earth Foundation in Nigeria. Bassey and others worry that eliminating entire populations of mosquitoes could have dangerous, unforeseen consequences.

BASSEY: It has the possibility of disrupting the balance in our ecosystems.

STEIN: But Muller and her colleagues say they are being extremely careful and plan to do a lot more research before even considering letting these gene-drive mosquitoes loose in the wild.

Rob Stein, NPR News.

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