US scientists work to breed malaria-free mosquitos

An Anopheles stephensi mosquito obtains blood from a human host. The species is a known malaria carrier.
An Anopheles stephensi mosquito obtains blood from a human host. The species is a known malaria carrier. REUTERS

WASHINGTON (AFP) - US researchers have carried out genetic tweaks to malaria-carrying mosquitos so their offspring feature genes that block the parasite which causes the disease, opening the way to eradicating it.

Previous studies in recent years had already shown it was possible to modify mosquitos genetically so they neutralise the parasite called Plasmodium falciparum, which causes malaria.

The new study, published Monday in Proceedings of the National Academy of Sciences, marks an advance in a gene-editing technique called Crispr.

It involves inserting parasite-blocking genes in the DNA of Anopheles stephensi mosquitos, which are a leading vector of malaria in Asia, to ensure that these genes are passed on to the bugs' offspring.

The researchers said they had achieved a rate of transmission of 99.5 per cent.

"This opens up the real promise that this technique can be adapted for eliminating malaria," said Anthony James, a professor of biology and molecular genetics at the University of California, Irvine and one of the main authors of the study.

In order to be sure that the gene-editing tool carrying malaria-blocking antibodies reaches the right piece of DNA, the researchers included an enzyme that gives the progeny red fluorescence in the eyes.

Almost 100 per cent of offspring - 99.5 per cent - exhibited this trait, proving that the genetic tweak worked.

James said further testing will be needed to confirm the efficacy of the anti-bodies, which could eventually lead to field studies.

"This is a significant first step," said James.

"We know the gene works. The mosquitoes we created are not the final brand, but we know this technology allows us to efficiently create large populations."

Malaria is one of the world's major health problems, as more than 40 per cent of the population lives in regions where they risk catching the disease.

Between 300 and 500 million new cases are diagnosed every year, and nearly one million people die of malaria each year, largely infants, young children and pregnant women, most of them in sub-Saharan Africa, according to the US Centres for Disease Control and Prevention.