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  Straits Times 14 Aug 06
New weapon in war on dengue being tested
by Meng Yew Choong

A NEW weapon in the war on dengue which could prove to be the ultimate WMD - Weapon of Mosquito Destruction - is now being tested in the Marsiling area.

One thousand of these mosquito traps, known as the gravitrap, are being field-tested to see how effective they are in capturing adult females looking for breeding grounds to lay their eggs, the National Environment Agency's chief executive, Mr Lee Yuen Hee, told The Straits Times.

He said: 'It's still experimental, and should the concept prove to be successful, NEA will consider giving each household a gravitrap.' The use of mosquito traps is not new. As part of its early warning system, the NEA uses beer-mug-sized devices, called ovitraps, to lure mosquitoes to lay their eggs inside them. Placed in public areas such as corridors, walkways or parks, the traps give the NEA an idea of the number and type of larvae hatched in the area under surveillance.

A large number of Aedes larvae will raise red flags that the population of the dengue-spreading mosquito in the area is likely to see an explosion.

The new gravitrap is an improvement on this design. By placing a layer of sticky material on the wire mesh, the mosquitoes will be trapped after laying their eggs. A similar low-cost and low-maintenance design is also being tested in Malaysia, The Straits Times understands.

And in the United States, there are dozens of commercially available mosquito traps which use carbon dioxide, light, warmth and moisture as lures to trap the insect. But these require a power source and are costly compared with the NEA design.

However, Mr Lee warned against relying solely on this potential silver bullet to solve the dengue problem.

Prevention is still the best control measure, he stressed. 'We have seen that breeding happens in objects and places like flower pots and discarded receptacles. It is fairly obvious that a lot of the breedings sites can be controlled, if only we care enough.'

His agency has been busy this year with pre-emptive strikes to keep the dengue problem in check after last year's record outbreak in which there were 14,209 dengue cases and 22 deaths.

From April, NEA officers working with volunteers sought out and destroyed breeding sites across the island, ahead of the warmer months, when it takes less time for mosquitoes to mature and multiply.

Their efforts have paid off. As of Aug 5, the number of dengue cases stood at 2,029, the lowest in four years. At this same point last year, 7,092 infections were recorded. The weekly average of 65 cases recorded this year was also well within the NEA target set by Mr Lee of keeping infections to under 100 a week.

The Ministry of Health considers 256 cases a week as the warning level and declares an epidemic if the number reaches 378. During the worst period of last year's outbreak, the number of cases reached 713 in a week.

Mr Lee added: 'While we cannot achieve a zero mosquito population, we can do our best to keep them at a minimal level. To do that, Singaporeans need to have a sense of ownership towards the environment.'
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