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Singapore

Dengue outbreak: Wolbachia mosquito project to be expanded to 1,400 more HDB blocks following 'promising' results

SINGAPORE: A project to fight dengue by releasing specially bred mosquitoes will be expanded to eight more public housing locations, covering an additional 1,400 HDB blocks.

The releases of male Wolbachia-Aedes mosquitoes in these new areas will start in July, Minister for Sustainability and the Environment Grace Fu announced on Wednesday (Jun 15).

Speaking on the third and last day of the Asia Dengue Summit taking place in Singapore, Ms Fu said this will cover 300,000 homes, up from the current 160,000. Coverage will go up from 19 per cent to around 31 per cent of all HDB blocks.

Project Wolbachia-Singapore involves the release of male mosquitoes infected with the Wolbachia bacteria. When these specially bred mosquitoes mate with urban female Aedes aegypti that do not carry Wolbachia, their resulting eggs do not hatch.

Releases will also take place at some construction sites and non-HDB residential sites in dengue high-risk areas, Ms Fu added.

"Besides reducing the population of Aedes aegypti mosquitoes in these areas, expansion will allow us to understand the impact of a large scale, multi-site deployment of Wolbachia technology on dengue cases," she said.

The eight new locations are Bedok North, Bedok Reservoir, Yew Tee, Geylang, Hougang, Punggol, Sengkang and Woodlands, estates considered “high-risk areas”, the National Environment Agency (NEA) said separately in a media statement.

The project currently covers around 1,800 HDB blocks across study sites in Yishun, Tampines, Choa Chu Kang and Bukit Batok towns, and within five square kilometres of landed estate at Marine Parade, comprising about 160,000 homes.

To support the expansion, NEA will increase the number of male Wolbachia-Aedes mosquitoes produced every week from the current 2 million to 5 million by the end of the year, through a collaboration with partners Orinno Technology, Verily Life Sciences and the National Robotics Programme.

In just six months, the number of dengue cases this year (14,000) has already exceeded the total for the whole of 2021, when 5,258 were reported, said NEA.

INTERRUPTING ACTIVE DENGUE CLUSTERS

The new sites for the Wolbachia project were chosen based on: Historical dengue risk level, Aedes aegypti population, the size and landscape of the area, and NEA's capacity for producing and releasing male Wolbachia-Aedes mosquitoes.

Besides suppressing the urban populations of the Aedes aegypti mosquito in these sites, data collected will also help to determine the impact of the technology on dengue cases and clusters, NEA said.

The Wolbachia technology will complement existing community efforts and vector control operations to reduce the dengue vector in Singapore, NEA said.

The tool has been shown to be useful for reducing the risk of dengue transmission in a local area, typically taking at least three to four months before there is a significant reduction of Aedes aegypti population.

SUCCESSFUL REDUCTION IN MOSQUITO POPULATION

The expansion of the project, which started in 2016, comes on the back of success in existing areas, NEA said.

Since April this year, NEA has achieved full coverage of male Wolbachia-Aedes releases in Tampines and Yishun, and started large-scale releases in the Marine Parade landed residential estate.

High-risk areas in parts of Choa Chu Kang and Bukit Batok HDB towns will also continue to get targeted releases of male Wolbachia-Aedes mosquitoes.

“The results have been promising thus far,” NEA said.

In Tampines and Yishun, where there has been more than one year of releases, NEA has previously observed up to 98 per cent reduction in the dengue mosquito population and up to 88 per cent reduction in dengue cases.

Similar observations have been made in the current dengue outbreak where these areas have 70 per cent fewer dengue cases compared to similar areas without Wolbachia, NEA said.

“The positive outcome of the field studies at release sites have shown that continued releases of male Wolbachia-Aedes mosquitoes can successfully suppress the female urban Aedes aegypti mosquito population in Singapore,” NEA said.

The expansion of the project to multiple sites is a “very exciting and important next step”, said Associate Professor Ng Lee Ching. She is the group director of the NEA's Environmental Health Institute.

She urged the public to do its part by removing mosquito breeding habitats, as having breeding sources of mosquitoes in the community would reverse the impact achieved by the technology

“Business-as-usual is not an option given the escalating threats of dengue,” said Professor Duane Gubler, Dengue, Expert Advisory Panel Chairman and Emeritus Professor at Duke-NUS Medical School.

He added that new technologies, including Wolbachia and dengue vaccines, provide new tools to complement and strengthen existing dengue control efforts, and prevent epidemic transmission of the disease.

“The results observed with Project Wolbachia to date are promising, but it is important for the Singapore community to realise that it is not the silver bullet that will control dengue alone,” he said.

“It is thus important for the community to continue staying vigilant and take steps to fight dengue.”

Source: CNA/ja(ac)

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