Wolbachia mosquitoes released in expanded Nee Soon, Tampines sites in next phase of study

Vanessa Lim Channel NewsAsia 22 Feb 19;

SINGAPORE: Male Wolbachia-carrying mosquitoes have been released in expanded sites in Nee Soon and Tampines, under the next phase of a study to reduce the Aedes mosquito population and fight dengue.

The third phase of the National Environment Agency's (NEA) Project Wolbachia kicked off on Friday (Feb 22), with the mosquitoes released at Nee Soon East and Tampines West sites that are 1.6 to 2.2 times larger compared to the trial area in phase two.

These male mosquitoes infected with the Wolbachia bacterium do not bite or transmit diseases. If they mate with an uninfected female mosquito, the resulting eggs will not hatch.

The purpose of expanding the sites is to determine if suppression of the urban Aedes aegypti mosquito population can be sustained in larger areas, said NEA.

In the long term, this will require strategies which can reduce the number of male Wolbachia-Aedes mosquitoes being released in an area, to make the technology more sustainable.

The expansion in study sites follows the success of phase two of the study, which was conducted between April 2018 and January 2019 at smaller areas in Nee Soon East and Tampines West.

It resulted in an 80 per cent drop in the urban Aedes aegypti mosquito population at the Nee Soon East study site and a 50 per cent drop at the Tampines West study site, NEA said.

Results from the second phase also proved that a larger release site yields better results.

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NEA's Environmental Health Institute (EHI) and local startup Orinno Technology have also developed a prototype of a "mosquito launcher", which is designed to store male Wolbachia-Aedes mosquitoes so that they can be easily transported and later, released at high-rise residential blocks.

EHI and Orinno Technology have jointly filed five intellectual property patents for various mosquito-related solutions. This includes a larvae counter and a pupae counter.

Other devices under development include an automated feeding system, a pupae separator and an adult mosquito sex sorter.

NEA said these devices will not only help to save manpower and costs, but will also ensure the consistency and quality of the male mosquitoes produced and released.

Source: CNA/ic(cy)

Sterile male mosquitoes released in Nee Soon East for NEA study to control dengue, Zika
Felicia Choo Straits Times 22 Feb 19;

SINGAPORE - Thousands of sterile male mosquitoes were released in Nee Soon East in the early hours of Friday (Feb 22) morning, as part of a National Environment Agency (NEA) study looking at reducing the incidence of dengue and Zika in Singapore.

Project Wolbachia marked the launch of the study's third phase, which aims to find out if the suppression of the Aedes aegypti mosquito population - the primary species responsible for transmitting the two diseases - can be sustained in larger areas, said the NEA.

It follows the successful reduction of the Aedes mosquito population in the trial sites of Nee Soon East and Tampines West to 20 per cent and 50 per cent respectively last month.

The role of the Wolbachia-Aedes mosquito, which does not bite or transmit diseases, is to control and reduce the Aedes mosquito population.

Eggs produced when a male Wolbachia-Aedes mosquito mates with a female Aedes mosquito will not hatch, limiting the number of mosquito larvae each female Aedes mosquito can produce.

"We anticipate that climate change is going to worsen the spread of mosquito-borne diseases, with higher temperatures... and increased rainfall," said Dr Amy Khor, Senior Minister of State for the Environment and Water Resources, who attended the launch on Friday.

The number of dengue cases has been on the rise since December last year, increasing by 560 cases to 1,071 cases last month, she added.

The National Environment Agency says that the increased Aedes mosquito population in the community, coupled with the high current number of dengue cases, may lead to a surge in case numbers this year.

"We still need to remember that the Wolbachia technology is still under research and it is not a silver bullet... We will use it as a complement to our existing mosquito control efforts, so community vigilance and action remain critical," she said.

On Friday, three of these male Wolbachia-Aedes mosquitoes were released for every person in Nee Soon East, but the NEA will adjust the number of mosquitoes to be released along the way to maintain the current mosquito population, or to suppress higher numbers in the expanded area.

Mosquitoes will be released twice-weekly around the HDB blocks and along common corridors of 84 blocks in Nee Soon East

The third phase sees an even greater number of households taking part in the study: 7,950 in Nee Soon East and 5,560 households in Tampines West.

Research on the project started in 2009 and the first phase of the field studies started in 2016.

The first small-scale field studies in Braddell Heights, Nee Soon East and Tampines West examined the behaviour of the Wolbachia-carrying Aedes aegypti in the urban environment, such as how far and high they fly, and how well they could compete with their wild counterparts to mate with females. The result was a 50 per cent suppression of the Aedes mosquito population.

The study has also resulted in several innovations from a tie-up between the NEA's Environmental Health Institute and local start-up Orinno Technology.

For instance, an improved larvae counter has shortened the time required to fill a tray of water with 4,000 larvae from two hours to less than three minutes, speeding up the mass production and sorting of the male Wolbachia-Aedes mosquitoes.

Another device, a pupae counter which counts and dispenses the desired number of male Wolbachia-Aedes pupae into each release container, is 15 times faster than manual counting methods.

On Friday, a lightweight and portable release device called the mosquito launcher was showcased, in addition to the usual method of releasing the mosquitoes from jars.

Other devices still under development are an automated feeding system, a pupae separator, and an adult mosquito sex sorter.

Five intellectual property patents have been filed for these devices, which have also attracted interest from other international programmes that are also producing male mosquitoes for suppression of the mosquito populations in their communities.

Mr Louis Ng, an MP for Nee Soon GRC and chairman of Nee Soon Town Council, also attended the launch.