Experts suggest releasing millions of sterile male mosquitoes to combat dengue

SINGAPORE - Expertsengaged by the National Environment Agency (NEA) have suggested Singapore release millions of sterile male mosquitoes to combat the spread of dengue.

Female mosquitoes that breed with these males, made sterile by infecting them with wolbachia bacteria, will lay eggs that will not hatch, thus reducing the mosquito population.

This in turn will reduce the spread of dengue, which has infected more than 16,000 people this year and killed three. About one in five patients diagnosed with dengue ends up in hospital, adding to the bed crunch.

Professor Ary Hoffmann from the departments of Zoology and Genetics at the University of Melbourne and a member of the expert panel, said tests in Australia have shown that the sterile males are as fit as normal mosquitoes in mating with the females.

He estimates that Singapore has between 250,000 and 500,000 male Aedes mosquitoes. To beat these males to the females, five times their number of sterile males will have to be released - and more than once.

However, he said Singapore could concentrate on dengue hotspots rather than flooding the whole country at one go.

If the NEA decides to go ahead with this plan after field trials, it will have to set up a breeding facility to get the required mosquitoes. This will not be difficult as one female mosquito can lay about 300 eggs, usually within 21 days.

Professor Duane Gubbler an epidemiologist at the Duke-NUS Graduate Medical School, another expert on the panel, said that Singapore already has "the most effective mosquito suppression programme in the world" so it is a continuation of the programme.

Prof Gubbler said the wolbachia bacteria alone will not be enough to prevent dengue, as it will be extremely difficult to kill off the entire Aedes population.

So other methods must continue, such as removing water that allows breeding, repellents to avoid being bitten, and vaccines when they become available, he said.

Both experts assured that there will be no danger to people or the ecology in releasing the genetically-modified mosquitoes.

NEA said on Friday that it would review the panel's recommendations, and continue working with relevant experts and stakeholders to ensure safe and effective use of wolbachia technology.