Singapore ramps up breeding 'Wolbachia' mosquitoes as dengue crisis escalates

Singapore will accelerate the production of its lab-grown male mosquitoes that are released into the community to suppress the mosquito population amid an alarming dengue outbreak in the tropical city-state.

Minister for Sustainability and the Environment Grace Fu on Wednesday said some five million male Aedes mosquitoes would be manufactured each week, up from two million previously.

These specially-bred mosquitoes carry Wolbachia, a bacteria, so when they mate with female urban mosquitoes, their resultant eggs do not hatch.

The goal is to eventually shrink the mosquito population and contain dengue, a mosquito-borne viral disease that has spread rapidly around the world in recent years.

Male ‘Wolbachia’ Aedes mosquitos being released in Singapore in 2020. The nation is to more than double its weekly release of the insects in the battle against dengue. PHOTO: Reuters

Singapore’s plans are part of an expansion of Project Wolbachia, which will, from July, cover 1,400 more public housing blocks (140,000 homes), in addition to the 1,800 blocks already included.

About 31 per cent of public housing in the city state will at that point be in the programme, up from 19 per cent at the moment.

Fu, announcing the expansion at the Asia Dengue Summit in Singapore, pointed out that the global threat of dengue – typically a tropical disease carried by mosquitoes, which can sometimes be fatal – will continue to escalate.

“The challenge we face is formidable,” she said, noting that urbanisation and climate change have created favourable conditions for mosquito breeding.

“Dengue and other mosquito-borne viruses are no longer just a problem of the tropics. Unconfined by borders or socioeconomic lines, they will challenge communities around the world.”

Male Aedes mosquitos carrying the Wolbachia bacteria are released on a housing estate test site in Singapore in 2020. PHOTO: Reuters

Several countries in Southeast Asia are already experiencing an uptick in dengue cases and taking precautionary measures.

Malaysia has reported close to 12,000 cases this year as of May, a 35 per cent increase compared to the same time last year, according to WHO data.

In Thailand, the island of Phuket has ramped up anti-dengue efforts, including “fogging” (using disinfectant sprayed from a fogging machine) educational institutions as students return to class.

In Singapore, there have been 14,000 dengue fever cases this year but what has been particularly worrying is an earlier-than-usual surge that began in March, ahead of the traditional peak dengue season from June to October.


“Weekly cases could very well surpass the record of 1,800 seen in 2020 and may even exceed 2,000 soon,” said Fu, the Singapore minister. Singapore saw its largest outbreak in 2020, with 35,000 cases and 32 deaths.

Fu, calling the situation “urgent”, noted that the dominant strain in the city state this year was the dengue virus serotype 3 or DENV-3, which has been rarely seen in Singapore. This means population immunity is low.

She hoped the expansion of the Wolbachia project, together with good environment management and other efforts to control mosquito populations (such as nets and sprays) could bring the dengue caseload down.

Past results have been encouraging. Singapore was the first to implement the Wolbachia technology in a high-rise, high-density urban tropical setting, releasing the first batch of lab-grown mosquitoes in 2016.

In the Tampines and Yishun neighbourhoods, where the programme has been ongoing for more than a year, the Aedes mosquito population has dropped by 98 per cent, and there has been an 88 per cent reduction in dengue cases.

In the current outbreak, these two areas have 70 per cent fewer cases compared to similar areas not under the programme.

This article was first published in South China Morning Post.


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