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  Today Online 30 Jul 07
Mozzie wipeout with a sci-fi touch
Sheralyn Tay sheralyn@mediacorp.com.sg

HE LOOKS like your average guy, but little do the ladies know: This male carries a lethal gene. Dispatched in millions to silently assimilate into society, these males have been bred to do one thing — wipe out the population.

This stuff of B-grade horror flicks is no screenplay, but the next frontier in the battle against mosquito-borne diseases such as malaria, yellow fever and dengue.

Since the 1970s, scientists have been working to reduce the mosquito population by trying to alter certain traits in them — usually in the males, as they do not bite — to make them less fertile or more resistant to disease-causing agents.

Another approach, which Today understands some Malaysian scientists are already working on, is to insert a "killer gene" into male Aedes mosquitoes so that when they mate, the gene passes into the eggs the female lays. This gene will ensure that the larvae that hatch die.

According to a Malaysian scientist, field research is expected to start soon, making it the first nation to try out this dengue control method. It is believed that Singapore, too, will be undertaking research in this area.

But gene-tinkering aside, scientists say the other challenge is to ensure that lab mosquitoes can compete in the wild and not lose out in the dating game.

Essentially this means they have to match their wild counterparts in the mosquito sexiness quotient. Early experiments with radiating mosquitoes did not sit well with female mosquitoes and petered out, simply because the sterile mosquitoes were less attractive as mates.

"They need have to have an equal if not added advantage over the wild mosquitoes," said Associate Professor Peter Preiser from Nanyang Technological University's School of Biological Science.

This is so that in the long run, they will be able to displace the normal population, he explained.

Research over the last 15 years has shown that lab-bred mosquitoes somehow lose their male mosquito charm.

But good news came in April this year, when scientists in the United States managed to design a mosquito both resistant to the malaria parasite and which was just as sexually attractive as wild male mosquitoes.

But even with the strongest lab mosquito, this research will still face a number of challenges.

Said Prof Preiser: "You need to be able to introduce enough male mosquitoes into the population that they can effectively compete with normal mosquitoes." Other factors such as the insect's mobility means it's hard to control and study them once they are released.

There are also ecological factors to consider.

According to Assoc Prof Chan Woon Khiong, chairman of the sub-committee for Research BioSafety within the Genetic Modification Advisory Committee, any future fieldwork in Singapore on transgenic mosquitoes must be first accompanied by extensive lab research and controlled field trials.

This may take three to five years or even longer. The research itself must also take into account the behaviour of mosquitoes, the environment (weather) and the population's existing immunity level.

"Researchers will therefore need to provide evidence that these factors, and the released genetically-modified organisms, will not pose any health problems or perturb the biodiversity of the ecosystem," said Assoc Prof Chan.
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