NEA to conduct a Phase 2 field study in Q2/2018 to address the unique challenges of Singapore’s high-density and high-rise urban landscape

Singapore, 8 December 2017 – The National Environment Agency (NEA) has concluded Phase 1 of its field studies as part of Project Wolbachia – Singapore. The Phase 1 field study, which commenced in October 2016, has met its objectives. Data collected on how high and far the male Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes can fly, how long they live and their mating competitiveness in actual field conditions, will contribute to future field studies.

2          The field study also revealed challenges which are unique to Singapore’s high-density and high-rise urban landscape. As such, the Dengue Expert Advisory Panel (DEAP) has advised NEA to conduct further field studies to strengthen NEA’s planning for the subsequent suppression trial. The Phase 2 field study will commence in the second quarter of 2018. More details, including the scope, locations and commencement dates of the Phase 2 study, will be announced when ready.

3          NEA’s careful and thorough studies, to be conducted over a timeframe of several years, is necessary to ensure the proper evaluation and application of the technology in our unique urban landscape. NEA is encouraged by the continual interest of the public in the project. We would like to express our appreciation to the various stakeholders, volunteers and residents who have supported the project thus far, and we hope to receive such support as we continue with the studies.

4          The Wolbachia technology, if proven effective, will further strengthen our capabilities to tackle dengue and other mosquito-borne diseases. This is especially crucial as higher global temperatures resulting from climate change can have an impact on the spread of mosquito-borne diseases and public health.

Background on Project Wolbachia – Singapore

5          NEA is evaluating the use of male Wolbachia-Aedes mosquitoes to further suppress the Aedes aegypti mosquitoes in the community. When these released male Wolbachia-Aedes mosquitoes mate with urban females in the community, the resultant eggs do not hatch. The continual release of male Wolbachia-Aedes mosquitoes is thus expected to reduce the viability of the Aedes eggs, and hence bring about a gradual reduction in the urban Aedes aegypti mosquito population.

6          The Phase 1 field study involved the release of male Wolbachia-Aedes mosquitoes to understand the behaviour and ecology of Aedes aegypti in our high-rise urban landscape. With the strong support of the residents and other stakeholders, the first field study was successfully conducted at three selected sites at Braddell Heights, Tampines West and Nee Soon East.

Key Findings of First Calibration Study

7          The Phase 1 field study has met its objectives and allowed us to obtain much valuable ecological information on the behaviour of mosquitoes in Singapore. The study also showed that half the Aedes mosquito eggs collected from the release sites did not hatch, demonstrating that the released male Wolbachia-Aedes mosquitoes had successfully competed with the urban male mosquitoes and mated with some of the urban Aedes aegypti females. Though not a key objective of the Phase 1 field study, the Aedes aegypti population correspondingly saw a 50 per cent suppression during the study. More information on the results of Phase 1 can be found in the Annex.

8          The field study identified two ecological challenges, peculiar to Singapore’s high density, high-rise housing, that should be addressed to attain a higher impact:

1. Movement of Aedes aegypti from the surrounding areas into the release sites; and
2. High Aedes mosquito density on high floors of some blocks, where insufficient numbers of male Wolbachia-Aedes reach.

Plans Moving Forward

9          As advised by the DEAP, NEA plans to conduct further field studies to strengthen our planning for the subsequent suppression trial. Improvements to the existing methods of production will also have to be explored, as very small releases of female Wolbachia-Aedes over time may eventually result in Wolbachia-Aedes taking over as the dominant mosquito strain, and hamper the continued use of Wolbachia-Aedes to suppress the Aedes population in those areas. Professor Duane Gubler, Chairman of the DEAP, and Founding Director of the Emerging Infectious Diseases Programme at Duke-NUS Medical School said, “NEA’s Phase 1 field study has garnered valuable data, but it is important that further field studies be conducted to address the unique challenges that were surfaced during the study so that future application of this exciting technology can proceed more effectively. For example, NEA needs to understand the potential barriers to immigration of the Aedes mosquito from non-intervention sites. Such barriers may include roads, expressways and parks. This underscores the complexity of the project, especially in such a dense urban city like Singapore. We know that studies of this kind are not easy but the DEAP is encouraged by NEA’s research to date and looks forward to the collection of even more valuable data.”   

Community Action Remains Key for Dengue Prevention

10        Whilst the Wolbachia-Aedes technology holds much promise as an additional tool for Aedes control, we must continue our effort in the elimination of mosquito breeding habitats. A strong integrated vector control programme with community participation remains essential for dengue prevention in Singapore. NEA urges everyone to continue to remain vigilant and practise the 5-step Mozzie Wipeout. Persons infected with dengue should protect themselves from mosquito bites by applying repellent regularly, and those showing symptoms suggestive of dengue should see their doctors early to be diagnosed. The latest updates on the dengue situation can be found on the NEA website, the Stop Dengue Now Facebook page and the myENV app.

Annex: Summary of Key Findings from Phase 1 Wolbachia Field Study [PDF, 337.87 KB]