Malaria
Mosquito sexing technique promosing in malaria control
By Imperial College London
Oct 11, 2005 - 12:59:00 AM

Scientists have genetically modified male mosquitoes to express a glowing protein in their gonads, in an advance that allows them to separate the different sexes quickly.

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

Research published online today in Nature Biotechnology, shows how a team from Imperial College London have altered male mosquitoes to express a green fluorescent protein in their gonads. Coupled with a high speed sorting technique, scientists will be able to identify and separate the different mosquito sexes much more easily than by manually sorting.

Professor Andrea Crisanti, senior author of the paper, from Imperial College London, said: "This advance could have enormous implications for controlling mosquito populations. Now that we can identify males and females at an early stage, it will be possible to release sterile males into the population without the risk of releasing additional females. The release of sterile males has proven effective in controlling several insect pests when methods for sorting sex are available.

"Female mosquitoes are responsible for spreading malaria, and also for damage to crops, but they are only able to breed once before dying. By forcing females to breed with sterile males, we can stop them creating additional mosquitoes and at the same time, reduce the population."

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

When the genetically modified mosquitoes were mixed with normal male and female mosquitoes, they found the females were as likely to breed with the modified mosquitoes as they were with the normal ones.

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

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

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