New GM Mosquito Sexing Technique Is Step Towards Malaria Control, Report Scientists

By providing a way to quickly sex mosquitoes, the advance paves theway for pooling large numbers of sterile males which could be used tocontrol the mosquito population.

Research published online today in Nature Biotechnology, showshow a team from Imperial College London have altered male mosquitoes toexpress a green fluorescent protein in their gonads. Coupled with ahigh speed sorting technique, scientists will be able to identify andseparate the different mosquito sexes much more easily than by manuallysorting.

Professor Andrea Crisanti, senior author of the paper, fromImperial College London, said: "This advance could have enormousimplications for controlling mosquito populations. Now that we canidentify males and females at an early stage, it will be possible torelease sterile males into the population without the risk of releasingadditional females. The release of sterile males has proven effectivein controlling several insect pests when methods for sorting sex areavailable.

"Female mosquitoes are responsible for spreading malaria, andalso for damage to crops, but they are only able to breed once beforedying. By forcing females to breed with sterile males, we can stop themcreating additional mosquitoes and at the same time, reduce thepopulation."

The team used the mosquito Anopheles stephensi, the mosquitoresponsible for much of the malaria in Asia. They engineered themosquito larvae to express an enhanced green fluorescent protein(EGFP). The modified larvae were mixed with normal larvae, and theresearchers were able to identify the modified male mosquitoes by theirfluorescent gonads.

When the genetically modified mosquitoes were mixed with normalmale and female mosquitoes, they found the females were as likely tobreed with the modified mosquitoes as they were with the normal ones.

This work builds on earlier work by the Imperial team publishedin 2000, demonstrating for the first time the insertion of a foreigngene into the mosquito genome. This raised the possibility that geneticmanipulation could be used as a control method in mosquito populations.

Professor Crisanti adds: "Although there have been a number ofcontrol programmes to eradicate malaria, none of these have beenentirely successful, and many have also had side effects, such asenvironmental damage through insecticides. This advance could one daymake a major impact on the burden of ill health caused by malaria, andis another step towards how genetic modification can be used safely todeal with global problems."