Can editing mosquito genes stop Zika?

Scientists are trying to find out more about the Zika virus and the mosquito which carries it (Getty)
Scientists are trying to find out more about the Zika virus and the mosquito which carries it (Getty)

In a world grappling with an outbreak of the Zika virus, scientists suggest editing the insects' genes could mean fewer blood-sucking females and therefore less mosquito-borne disease.

In a study published in Cell Press today, researchers say the recent discovery of the first male-determining factor in mosquitoes combined with the gene-editing capability of the CRISPR-Cas9 could lead the more harmless, nectar-feeding males.

Zach Adelman, an entomologist at Virginia Tech, says experts are at a critical point in their knowledge of mosquitoes.

"We are at a turning point both in our understanding of how mosquitoes determine whether to become a male (a good choice for us) or a female (trouble for us), as well as our ability to permanently modify wild populations using gene drive techniques," he says.

Attempts to control dengue fever based on releasing sterile, transgenic mosquitoes are currently underway and have been successful where tried, but the cost is high and the method impractical.

Associate professor Adelman and co-author Zhijian Tu say that method requires long-term releases and difficult to do in large-scale.

They say a potentially more effective and cheaper method could be to drive the maleness gene with the CRISPR-Cas9 which shows promise as easy, efficient and precise approach to introduce mutations in a wide range of organisms.

The pair published a study in May where they found the first male-determining factor in mosquitoes in a sex-determination gene called Nix.

In female embryos, the presence of Nix triggered the development of external and internal male genitalia.

The gene is also needed to start male development in Aedes aegypti -- the type of mosquito which carries dengue and yellow fever, Zika and Chikungunya viruses.

"This discovery sets the stage for future efforts to leverage the CRISPR-Cas9 system to drive maleness genes such as Nix into mosquito populations, thereby converting females into males or simply killing females," Dr Tu says.

But before this becomes reality, the authors say there are a number of questions and ethical concerns which need answering.

For example, they're unsure how Nix controls sex determination and whether it is conserved across species which transmit different diseases.

The effectiveness and long-term stability of the method in mosquitoes is also unknown and it is also not clear how to remove the introduced gene from a study area if needed.

Fears of bioterrorism have prompted some to call for the prohibition of public discussion the process of 'gene-driving' and there aren't clear regulatory or ethical guidelines around the method yet.

Dr Adelman says this minefield of concern mean any practical applications would be in places where the disease burden is high, other controls aren't successful, the public are behind the programme and there is a regulatory structure.