Vietnam cuts Aedes population using natural foes

SINGAPORE - Vietnam's experiments with biological agents to reduce the mosquito population in the country appear to be bearing fruit.

One is the use of a crustacean called Mesocyclops to control mosquito larvae, the other is the introduction of an Australian bacterium called Wolbachia into the Aedes mosquito.

The bacterium, found naturally in some insects, reduces the lifespan of the Aedes mosquito as well as the viability of their eggs.

More importantly, this bacterium blocks dengue virus transmission, said Professor Nguyen Tran Hien, director of Vietnam's National Institute of Hygiene and Epidemiology.

After seven years of tests on the Aedes mosquitoes infected with the Wolbachia bacteria - including making sure that they pose no risk to humans - Vietnam decided to do a pilot test on Tri Nguyen island, home to 3,250 people.

In April, it released the first batch of infected mosquitoes on this island.

Ten weeks later, these Wolbachia-infested mosquitoes have gained dominance and now are found in 71.4 per cent of mosquitoes there. The bacteria are passed on to offspring.

The other biological agent Vietnam uses is the Mesocyclops, a tiny crustacean, to rid water of mosquito larvae.

They are bred and released into tanks, water barrels and other water bodies.

They feed on larvae, leaving almost none to turn into mosquitoes.

As a result, the mosquito population where these are used has fallen dramatically, said Prof Nguyen.

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