Wolbachia mosquitoes to be released in Chua Chu Kang, Bukit Batok, identified as high-risk dengue areas

SINGAPORE — The National Environment Agency (NEA) will release male Wolbachia-carrying Aedes aegypti mosquitoes at 207 blocks of flats in Chua Chu Kang and Bukit Batok this month.

The selected neighbourhoods have high Aedes aegypti mosquito populations and are at greater risk of having dengue clusters forming there, NEA said in a statement on Wednesday (May 6).

From January to mid-April, almost 5,800 dengue cases were reported, more than double the figure for the same period in 2019.

NEA warned that with the arrival of the dengue peak season from May to September, the number of dengue cases this year is projected to surpass 2019's 16,000 cases, unless immediate measures are taken.

NEA added that weekly figures, which range between 300 and 400 cases, remain high and continue to be a public health concern.

Separately, Mr Masagos Zulkifli, Minister for the Environment and Water Resources, said in a Facebook post that NEA had observed a 50 per cent increase in breeding sites found in homes over the last three years, compared with the preceding three years.

The Aedes aegypti mosquito is the primary vector of the dengue, chikungunya and Zika viruses in Singapore.

Under Project Wolbachia, which was launched in 2016, male mosquitoes are infected with the Wolbachia bacteria and then released to mate with female mosquitoes. The eggs produced will not hatch because they are biologically incompatible.

The Wolbachia-infected mosquitoes have been released in several sites in Yishun and Tampines.

“We have achieved more than 90 per cent suppression of the urban Aedes aegypti mosquito population at existing study sites at Yishun and Tampines towns, and have kept these populations at low dengue-risk levels for more than a year,” NEA said.

The agency's preliminary analysis of 2019 data also showed that there were 65 to 80 per cent fewer dengue cases at the Yishun and Tampines sites where the Wolbachia-infected mosquitoes had been released, compared with other areas.

It said that residents in the selected neighbourhoods in Chua Chu Kang, Keat Hong and Hong Kah North do not have to do anything differently, and should continue to stay vigilant and carry out mosquito control procedures as usual.

NEA will also continue with the current releases at Yishun and Tampines, which involve 553 blocks of flats.

“While the results so far indicate that Wolbachia-Aedes mosquito releases are effective at suppressing the urban Aedes aegypti mosquito populations as well as dengue cases, the technology is not a silver bullet,” NEA said.

They are intended to complement rather than replace traditional vector control measures, which include comprehensive mosquito surveillance, source reduction of mosquito breeding habitats, and the use of insecticides where necessary, the agency added.

“It is therefore critical for the public to remain vigilant and regularly practise the Mozzie Wipeout, so that our neighbourhoods and homes can be kept free of mosquitoes and dengue,” NEA said.