SINGAPORE: Releasing mosquitoes to fight dengue may sound counterintuitive, but Singapore has spent more than a decade developing the approach to tackle the problem.

Project Wolbachia, which started in 2016, uses specially bred male mosquitoes to suppress the Aedes aegypti population and reduce the risk of dengue.

The project followed years of laboratory research and risk assessments, spurred in part by one of Singapore’s worst dengue outbreaks in 2013, when more than 22,000 cases were reported.

The high number of cases gave researchers added impetus to look for new ways to control the mosquito population, Dr Chong Chee-Seng, director of environmental epidemiology and toxicology at the Environmental Health Institute, told CNA.

“That really spurred us in terms of research,” said Dr Chong, who has since helped take Project Wolbachia from the laboratory to housing estates across the island. 

WINNING PUBLIC ACCEPTANCE

But when researchers first began exploring the use of Wolbachia, there was no guarantee the idea would take off.

For years, the message from authorities has been to prevent mosquitoes from breeding, making the idea of deliberately releasing them into residential areas a potentially difficult one to sell, said Dr Chong.

“The only question is – if we release mosquitoes, can people accept it?”

Researchers were considering a number of technologies at the time, but Wolbachia caught their attention because it is naturally present in many insects.

The bacterium is found in more than 60 per cent of insect species, including butterflies, Dr Chong said.

“We thought Wolbachia is something that we should explore, and hence we started the laboratory assessment.”

Under the project, male Aedes aegypti mosquitoes carrying Wolbachia are released to mate with females in the wild.

Their resulting eggs do not hatch, suppressing the mosquito population over time.

Only males are released, and they do not bite – a fact that became central to explaining the project to residents.

“So our key message, what we are educating people, is that male mosquitoes don’t bite,” Dr Chong said, adding that this was important in helping people accept the releases.