Wolbachia Technology

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What is Wolbachia and does it harm humans and animals? Are Wolbachia-carrying mosquitoes considered as having been genetically modified?

Wolbachia are naturally occurring bacteria found in more than 60 per cent of insects around us, including butterflies, dragonflies, fruit flies, and various mosquito species such as Aedes albopictus, but not in the primary dengue vector mosquito Aedes aegypti. Wolbachia have not been shown to infect humans or other mammals, even when carried by biting insects.

The Wolbachia-carrying Aedes aegypti mosquito is not considered a genetically modified organism, as confirmed by the Genetic Modification Advisory Committee (GMAC) in Singapore. This is because there is no tampering or modification of the genes of the mosquito. Wolbachia technology is considered a biological control method.

NEA is conducting studies on the feasibility of using Wolbachia-carrying male Aedes aegypti mosquitoes to help suppress the Aedes mosquito population. Male mosquitoes do not bite or transmit disease. Studies have shown that female Aedes aegypti mosquitoes, after mating with male Aedes aegypti mosquitoes that carry Wolbachia, produce eggs that do not hatch. This can help reduce the population of Aedes mosquitoes over time by suppressing their reproduction. This suppression approach is no different from our current emphasis on source reduction of the Aedes mosquito.

Public health and safety are our paramount concern. In June 2014, NEA appointed a Dengue Expert Advisory Panel to provide professional advice on the studies of such new technologies for dengue control. Having reviewed the latest scientific literature underlying these new modalities, Singapore's dengue epidemiology, and data derived from the multi-disciplinary studies conducted at NEA's Environmental Health Institute (EHI), the Panel has, in October 2014, recommended that Singapore explores the use of Wolbachia-carrying Aedes aegypti males to help suppress the Aedes mosquito population in Singapore, for further reduction of the risk of dengue. It also recommended further studies, entailing the field release of Wolbachia-carrying Aedes aegypti males. However, the Panel emphasised that the implementation of such new tools should not preclude continuation of ongoing surveillance and mosquito control efforts.

"Wolbachia-carrying Aedes has been released in several places, such as Australia, Brazil, Indonesia and Vietnam, with no negative impact on public health and ecology. This is consistent with our knowledge and assessment. Wolbachia provides a safe strategy, because the bacteria are naturally present in a large fraction of insects. Organisms in the natural environment have been continuously exposed to Wolbachia for millions of years," explained Professor Ary Hoffmann, an expert on Wolbachia-insect interaction, from the University of Melbourne in Australia.

Professor Duane Gubler, Chairman of the Dengue Expert Advisory Panel, and Founding Director of the Emerging Infectious Diseases Program at Duke-NUS Graduate Medical School, added: "The approach with Wolbachia-carrying Aedes males will likely be most effective when used in combination with other methods of control such as the current community-based removal of potential breeding habitats, and a vaccine when available. Because of differing ecology, epidemiology and demographics, each country will have to develop a strategy that is most appropriate for the local situation. Singapore, with its comprehensive dengue surveillance and control system, coupled with a strong research culture, is an ideal place to assess this approach in the context of its existing dengue control programme."

NEA will review the details of the recommendations, and continue working with relevant domain experts and stakeholders to develop the framework for the safe and effective adoption of Wolbachia technology. We will only consider conducting such trials in Singapore if we are convinced that the methods proposed are safe and effective.

While NEA explores new technologies to fight dengue in future, we still need to address the here and now. Source eradication of mosquito breeding habitats remains key to preventing mosquito breeding. All stakeholders must continue to play their part to help stem dengue transmission in the environment, by checking their premises daily for potential mosquito breeding habitats and removing them. Those infected with dengue should protect themselves from mosquito bites by applying repellent as regularly as possible, and those showing symptoms suggestive of dengue, should see their GPs early to be diagnosed.