SINGAPORE: Early findings from an ongoing six-month study showed that the viability of Aedes aegypti mosquito eggs collected from a site at Tampines West has been reduced by about half, said the National Environment Agency's (NEA) Dengue Expert Advisory Panel (DEAP) on Wednesday (Feb 8).
The small-scale field study involves releasing male Wolbachia-carrying Aedes aegypti mosquitoes to understand their behaviour and see if they can suppress the population of urban Aedes aegypti mosquitoes.
While the male mosquitoes may fly around and enter homes to seek out females and find shelter, they will not bite or transmit disease. Eggs produced from the male Wolbachia-carrying Aedes aegypti mosquito and a female urban Aedes aegypti mosquito will not hatch.
Since October 2016, these male Wolbachia-carrying Aedes aegypti mosquitoes have been released on a regular basis at three selected sites located at Braddell Heights, Nee Soon East and Tampines West.
These estates have seen dengue outbreaks previously and have Aedes aegypti mosquitoes present in the environment.
Professor Neil Ferguson, a DEAP member, explained the significance of the findings from the study: "This is important because it indicates that the male Wolbachia mosquito can successfully mate with Aedes aegypti female mosquito and that's what we need to drive down the mosquito population."
In addition, the study found that male Wolbachia-carrying Aedes aegypti mosquitoes are able to live up to four days after being released in the urban environment, and can fly up to high levels and travel more than 40m horizontally.
DEAP chairman Professor Duane Gubler, said: "This suggests that they are as fit as male wild Aedes aegypti mosquitos. It tells us how frequently you have to release these mosquitos, so that we can better calibrate their releases."
MORE WOLBACHIA-CARRYING MOSQUITOES MAY BE RELEASED
The study, called Project Wolbachia-Singapore, has made "good progress" and yielded "valuable data to guide the next phase of trials", said NEA in a media release on Wednesday.
It added that over the next few months, more data will be collected to refine the design of the larger suppression trial planned for later this year.
The suppression trial will test the utility and effectiveness of releasing male Wolbachia-carrying Aedes aegypti mosquitoes to surpress the Aedes aegypti mosquito population.
"Nothing the panel has seen has caused any hesitation in proceeding with the project. But there's a lot to be learnt before the decision to expand the project can be made,” said Prof Gubler.
To do that, experts have suggested tweaking the study to increase the number of male Wolbachia-carrying Aedes aegypti mosquitos being released.
"Right now, the preliminary data doesn't get us the results we want to see,” explained Prof Gubler. “We need to increase the number of mosquitos to be released to see a larger impact."
NEA appointed the DEAP in June 2014 to provide professional advice on new methods of dengue control, particularly on the use of Wolbachia-carrying male mosquitoes.