Can genetically modified ‘killer mosquitoes’ stop the Zika virus?

This article was published at Spectator Health on 26 January 2016.

The forecast for the Zika virus outbreak seems dire. There is no vaccine, and no hope of one for at least a year, probably longer. And, according to the World Health Organisation, it is likely to spread to every country in the Americas apart from Canada and Chile.

Women in El Salvador have already been told to leave off getting pregnant until 2018, as it seems likely the virus causes brain damage in infants. Of course, this does not seem very realistic.

While North and South Americans wait for a vaccine, the best hope may lie in targeting the Zika carriers: the mosquitoes. And scientists in Oxford have developed an extraordinarily deadly means of doing so.

A company called Oxitec, set up by scientists from Oxford University, has produced a form of genetically modified mosquito whose offspring do not survive. By releasing millions of these GM males into an area to mate with potentially virus-carrying females they can lower the mosquito population by nine-tenths in a matter of months. (The GM males die quickly too, having been programmed to survive on a special diet in a lab.)

Trials on the Aedes aegypti mosquito — the mosquito transmitting the Zika virus – have already been carried out in Brazil. The target of the trial was not Zika, but dengue fever, and in Eldorado, Sao Paolo, where the GM mosquitoes were released, the number of dengue cases dropped from 133 to just one in a year.

The Oxitec mosquitoes are still being reviewed by the US Food and Drug Administration and a plan to use them in Florida met fierce opposition following headlines about ‘genetically modified killer mosquitoes’.

If taken up by the governments of the Americas they could be a key weapon against the Zika virus, alongside more routine methods of mosquito-avoidance. The challenge will be to scale up their production quickly enough to make a difference.

In the longer term they may well be crucial in efforts to combat other mosquito-borne disease — dengue fever, chikungunya, yellow fever, malaria — by keeping the mosquito population at a very low level. It tentatively raises hopes that the mosquito may one day no longer be such a deadly enemy for humans.