Scientists battling malaria said this week they have produced a strain of mosquitoes carrying genes that block the disease's transmission, with the idea that these insects could breed with other members of their species in the wild and produce offspring that can’t spread the illness.
The researchers said Monday they used gene-editing — a technique by which DNA can be inserted, replaced or deleted from a genome, on a mosquito species called Anopheles stephensi that spreads malaria in urban India.
They inserted DNA into the species’ germ line, cells that pass genes from generation to generation. This created mosquitoes with genes that produce malaria-blocking antibodies, which are passed to 99.5 percent of offspring.
The research was published Monday in the Proceedings of the National Academy of Sciences.
Malaria is caused by parasites transmitted to people through the bites of infected female mosquitoes. The goal of the new research is to release genetically modified mosquitoes to mate with wild mosquitoes so that their malaria-blocking genes enter the gene pool and eventually overrun the population, short-circuiting the species' ability to infect people with the parasites.
"It can spread through a population with great efficiency, increasing from 1 percent to more than 99 percent in 10 generations, or about one season for mosquitoes," said University of California-San Diego biologist Valentino Gantz.
Ethan Bier, another UC-San Diego biologist, called the experiment a "potent tool in sustainable control of malaria," as all the mosquitoes in a given region would carry anti-malarial genes.
"We do not propose that this strategy alone will eradicate malaria," University of California-Irvine molecular biologist Anthony James said.
But in conjunction with treatment and preventive drugs, future vaccines, mosquito-blocking bed nets and eradication of mosquito-breeding sites, it could play a major role in sustaining the elimination of malaria, James said.
Other scientists also have been working to create genetically engineered mosquitoes. One group last year said it created a strain carrying a gene leading nearly all offspring to be male, which could cause wild populations to plummet.
"In contrast, our much more flexible system only prevents mosquitoes from carrying malaria but can be used to do no harm to the mosquito. So it should generate the least amount of ecological damage," Bier said.
The World Health Organization estimates that in 2015 there will be 214 million malaria cases and 438,000 deaths, most in sub-Saharan Africa.