Having achieved more than 90 per cent suppression of the urban Aedes aegypti mosquito population in the study sites at Nee Soon East and Tampines West, the project will now progress to an expanded Phase 4 field study in November 2019
Singapore, 7 October 2019 – The Phase 3 field study of Project Wolbachia – Singapore has achieved more than 90 per cent suppression of the urban Aedes aegypti mosquito population at the Nee Soon East and Tampines West study sites. In November 2019, the National Environment Agency (NEA) will extend the release of male Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes to more neighbourhoods at Nee Soon East and Tampines West. To support this Phase 4 field study, NEA will scale up production and releases with a new mosquito production facility and the use of technologies.
Phase 3 Field Study Yields Promising Results
2 NEA is conducting phased field studies to evaluate the use of male Wolbachia-Aedes mosquitoes to suppress the urban Aedes aegypti mosquito – the primary vector of dengue, chikungunya and Zika viruses in Singapore. When the released male Wolbachia-Aedes mosquitoes mate with urban female Aedes aegypti mosquitoes, the resulting eggs do not hatch. Over time, continued releases of male Wolbachia-Aedes mosquitoes are expected to bring about a gradual reduction in the urban Aedes aegypti mosquito population, and hence lower the risk of dengue transmission.
3 In the ongoing Phase 3 field study, Project Wolbachia – Singapore achieved more than 90 per cent suppression of the urban Aedes aegypti mosquito population at the study sites, comprising 84 and 60 residential blocks at Nee Soon East and Tampines West, respectively (Annex A, Figure 1). This is an improvement on the 70 to 80 per cent suppression achieved at the conclusion of the Phase 2 field study in December 2018, and demonstrates the effectiveness of Wolbachia-Aedes technology in Singapore’s high-rise and high-density urban landscape.
4 Importantly, continued releases have kept the Aedes aegypti mosquito population at levels that pose low dengue risk. The Aedes aegypti mosquito population in an area is measured by the average number of Aedes aegypti mosquitoes caught in each Gravitrap in the area. At some release areas, the numbers caught per trap plunged from more than 1 before the release, to as low as 0.015 during the release.
5 Professor Duane Gubler, Chairman of the Dengue Expert Advisory Panel (DEAP) and Founding Director of the Emerging Infectious Diseases Programme at Duke-NUS Medical School, said: “NEA has completed seven years of extensive biological and ecological studies on male Wolbachia-carrying mosquito releases to suppress the urban mosquito population in Singapore. These have been the most comprehensive and exhaustive studies ever done, to determine how best to safely and effectively use this method in Singapore. We are optimistic that this method, when fully implemented, will tip the balance in favour of dengue control.”
Expansion of Release Sites in Phase 4 Field Study
6 With the success of the Phase 3 field study, Project Wolbachia – Singapore will progress to a Phase 4 field study in November 2019. To determine if the Aedes aegypti mosquito population suppression can be sustained over larger areas, NEA will expand the Nee Soon East and Tampines West release sites to cover 163 and 121 residential blocks, respectively. This new phase will entail a nearly two-fold expansion in release area size compared to in Phase 3, and an about seven-fold expansion compared to in Phase 1 (Annex B shows location maps of the study sites).
7 Associate Professor Ng Lee Ching, Director of NEA’s Environmental Health Institute, said: “The larger areas in Phase 4 will help us to demonstrate better efficacy, in other words, to achieve the same success with a smaller number of male Wolbachia-Aedes mosquitoes released at each block. Our systematic approach is needed to derive good comparative results, and a consistent and comprehensive dataset, to ensure robustness of the study before scaling up to more areas beyond Yishun and Tampines.”
Scaled-up Production and Releases
8 The success of the study is facilitated by our successful collaborations with Verily and Orinno Technology Pte. Ltd., and the incorporation of engineering technologies and data analytics.
9 Moving forward, NEA will scale up production and releases with a new mosquito production facility, and will continue to develop technologies to improve efficiency and productivity. To this end, the Phase 4 field study will involve testing the use of drones for efficient releases of Wolbachia-Aedes mosquitoes at some areas of the study sites. NEA will continue to work with Orinno Technology Pte. Ltd. and Verily, to use and test their automation solutions to enhance efficiency and quality in the production and release of Wolbachia-Aedes mosquitoes.
Wolbachia Technology to Complement Existing Vector Control Efforts
10 Singapore will continue to face challenges in the fight against dengue and other mosquito-borne diseases. The main vector of dengue – the Aedes aegypti mosquito – thrives in urban settings. It breeds in artificial containers and dwells mainly indoors, sheltered by the roofs and walls of our city. In addition, global warming will threaten to increase the vector population in our community and will increase virus replication, therefore resulting in an increase in dengue transmission. Disease epidemics will be further intensified by the low prevalence of protective antibodies in the population – low herd immunity. As such, there is no room for complacency, and efforts to test novel vector control solutions must continue.
11 Even as Project Wolbachia – Singapore continues to show good results in keeping the Aedes aegypti mosquito population low, the technology is not a silver bullet. Breeding of mosquitoes in the community will cancel out the positive impact of the technology. It is therefore important that the community continues to prevent and remove mosquito breeding habitats, so that fewer male Wolbachia-Aedes mosquitoes have to be released for the technology to be successful. If successful, the Wolbachia technology will form part of Singapore’s dengue control programme, comprising comprehensive mosquito surveillance, source eradication of mosquito breeding habitats, and spraying of insecticide where necessary to control the adult mosquito population.
12 The success of Project Wolbachia – Singapore thus far is attributed to the strong support from community partners and residents, who are doing their part in keeping their premises and homes free of mosquito breeding habitats, and are providing valuable feedback. As the project progresses to Phase 4, residents at the study sites do not have to do anything differently, but continue to carry out mosquito control procedures and practise the 5-Step Mozzie Wipeout as normal.
13 Members of the public can find out more about Wolbachia technology by visiting www.nea.gov.sg, or contacting NEA at 1800-CALL-NEA (1800-2255 632) if they have any enquiries. We are thankful for the support from residents, stakeholders and the community.
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MOSQUITO POPULATION SUPPRESSION IN THE PHASE 1, 2 AND 3 FIELD STUDIES
Wolbachia technology has the potential to suppress the Aedes aegypti mosquito population in the community.
In the Phase 3 field study, more than 90 per cent suppression of the urban Aedes aegypti population was achieved at the study sites. This is an improvement from the previous phases, and demonstrates that male Wolbachia-Aedes releases can be used to successfully target Aedes aegypti mosquitoes in Singapore’s high-rise and high-density urban landscape.
Fig. 1. Phase 3 – Infographic showing the impact of male Wolbachia-Aedes mosquitoes on the urban Aedes aegypti mosquito population at the study sites
LOCATION MAPS OF STUDY SITES