GM-mosquitoes lead warfare on dengue

Men with truckloads of mosquitoes in containers enter a remote village in dengue-threatened Panama. They are there to control the mosquito population, but instead they release thousands of Aedes aegypti mosquitoes into the area.

The male mosquitoes that are released have been genetically modified to produce offspring which die before reaching maturity.

British company Oxitec is behind this novel warfare on dengue.

During a recent visit to Singapore, its chief executive, Mr Hadyn Parry, told My Paper that after a successful trial at a Brazilian village where the mosquito population was brought down by 90 per cent over six months, his team is now moving into Panama.

Earlier this month, the National Technical Commission for Biosecurity - the body responsible for approval and regulation of transgenic organisms in Brazil - also approved the commercial release of the genetically modified mosquito developed by Oxitec.

This approach is more environmentally friendly than using insecticides, said Mr Parry. "Almost every other way to combat mosquitoes tends to use products that stay in the environment and will probably kill other insects as well. With our approach, you are just targeting that one insect that is causing the problem," he said.

Also speaking to My Paper was Professor Steven Sinkins, a British scientist who is researching the use of a naturally occurring bacterium - Wolbachia - to fight the dengue virus.

By transferring the Wolbachia bacterium into Aedes aegypti mosquitoes, Prof Sinkins and his team were able to reduce the mosquitoes' ability to transmit the dengue virus. Wild females which mate with male mosquitoes with Wolbachia also produce eggs which do not hatch.

The bacterium does not affect humans, said Prof Sinkins. "It originates from fruit flies, so even if humans are eating any fruit they are probably eating little bits of Wolbachia from the fruit flies. It doesn't do any harm," he said.

Almost 100 per cent frequency spread of Wolbachia was achieved within four months at trials done in northern Australia and similar trials are being brought to the region, in Nha Trang, Vietnam, and Yogyakarta, Indonesia.

But could this be a possibility for Singapore?

Last year, it was reported that the National Environment Agency's Environmental Health Institute was conducting laboratory studies to test the potential and risks in the Singapore context.

Dengue expert Duane Gubler said these methods are "promising". He notes that more field work has to be done, but is hopeful that both methods would be fully tested within the next five years.

But even then, it would have to be used together with vaccines, said Professor Gubler, who is with the Duke-NUS Graduate Medical School Singapore's emerging infectious diseases programme.

"Suppressing dengue by mosquito control alone will not work, no matter what type of methods," he said.

"The way to do so is to use promising mosquito control methods and combine them with vaccination and anti-viral drug."

samboh@sph.com.sg

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