Singapore may release sterile mozzies to combat dengue

These can fight with virile males for mates and weaken Aedes population

This article was first published on Oct 18, 2014

If the males shoot blanks, female mosquitoes will not be able to create new dengue-spreaders.

That is why Singapore could be releasing millions of sterile male mosquitoes here, if field studies are successful, say experts who have backed the plan.

The special mosquitoes have been genetically modified to contain a form of bacteria that makes them incapable of fertilising eggs. They also cannot spread dengue and are harmless to people.

These special mosquitoes will compete with virile males for mates and hopefully decimate the Aedes mosquito population, which this year alone has landed thousands of people in hospital, killing three.

The National Environment Agency, which tasked a panel with studying the use of the Wolbachia bacteria to fight dengue, yesterday said it will review the details of its recommendations.

It will also continue working with experts and stakeholders to develop the framework for the safe and effective adoption of the technology.

The bacteria is found in many insects but not the dengue- spreading Aedes mosquito.

Panel member Ary Hoffmann, from the departments of zoology and genetics at Australia's University of Melbourne, explained that female mosquitoes breeding with the sterile males will lay eggs that will not hatch, thus reducing the mosquito population.

Dengue, which is endemic in the region, has infected more than 16,000 people in Singapore this year. Roughly one in five patients diagnosed with the disease ends up in hospital, adding to the bed crunch.

Work on genetically modifying the Aedes mosquito has been going on for almost a decade, with five countries - Australia, Vietnam, Indonesia, Brazil and Colombia - doing field tests.

Another panel member, epidemiologist Duane Gubler from Duke-NUS Graduate Medical School, said that releasing the new mosquitoes would not harm people or the environment.

Professor Hoffmann estimates that Singapore has between 250,000 and 500,000 male Aedes mosquitoes. For the plan to be effective, five times those numbers of sterile males will have to be released - and more than once.

But he noted that the country could concentrate on dengue hot spots rather than flooding the whole country at one go.

Professor Gubler stressed that the Wolbachia bacteria is not a magic bullet. Other methods such as removing water that allows breeding must continue, he said.

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