Singapore may release sterile mozzies to combat dengue

Salma Khalik The Straits Times AsiaOne 18 Oct 14;

SINGAPORE - If the males shoot blanks, female mosquitoes will not be able to create new dengue-spreaders.

That is why Singapore could be releasing millions of sterile male mosquitoes here, if field studies are successful, say experts who have backed the plan.

The special mosquitoes have been genetically modified to contain a form of bacteria that makes them incapable of fertilising eggs. They also cannot spread dengue and are harmless to people.

These special mosquitoes will compete with virile males for mates and hopefully decimate the Aedes mosquito population, which this year alone has landed thousands of people in hospital, killing three.

The National Environment Agency, which tasked a panel with studying the use of the Wolbachia bacteria to fight dengue, yesterday said it will review the details of its recommendations.

It will also continue working with experts and stakeholders to develop the framework for the safe and effective adoption of the technology. The bacteria is found in many insects but not the dengue- spreading Aedes mosquito.

Panel member Ary Hoffmann, from the departments of zoology and genetics at Australia's University of Melbourne, explained that female mosquitoes breeding with the sterile males will lay eggs that will not hatch, thus reducing the mosquito population.

Dengue, which is endemic in the region, has infected more than 16,000 people in Singapore this year. Roughly one in five patients diagnosed with the disease ends up in hospital, adding to the bed crunch.

Work on genetically modifying the Aedes mosquito has been going on for almost a decade, with five countries - Australia, Vietnam, Indonesia, Brazil and Colombia - doing field tests.

Another panel member, epidemiologist Duane Gubler from Duke-NUS Graduate Medical School, said that releasing the new mosquitoes would not harm people or the environment.

Professor Hoffmann estimates that Singapore has between 250,000 and 500,000 male Aedes mosquitoes. For the plan to be effective, five times those numbers of sterile males will have to be released - and more than once.

But he noted that the country could concentrate on dengue hot spots rather than flooding the whole country at one go.

Professor Gubler stressed that the Wolbachia bacteria is not a magic bullet. Other methods such as removing water that allows breeding must continue, he said.

Fight dengue with mozzies carrying Wolbachia, say experts
Today Online 18 Oct 14;

SINGAPORE — A panel of experts has recommended that Singapore conduct studies involving the release of male Aedes mosquitoes carrying the Wolbachia bacteria into the field, to combat the dengue problem.

The aim is to get these Wolbachia-carrying males to mate with female Aedes mosquitoes, causing them to produce eggs that do not hatch and, ultimately, clamp down on the Aedes population and dengue transmission.

In June, the NEA appointed experts from Singapore, Australia, the United Kingdom and the United States to form a Dengue Expert Advisory Panel, to look into the use of biological control methods to limit the spread of dengue.

While the use of the bacteria has been tested in the laboratory by the NEA’s Environmental Health Institute, it has not been tested in the field. The NEA stated yesterday that the panel concluded that the proposed approach holds promise, and field trials are needed to prove its feasibility and effectiveness.

“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,” said Professor Ary Hoffmann, an expert on Wolbachia-insect interaction from the University of Melbourne in Australia. Male mosquitoes also do not bite or transmit disease.

The NEA said it would review the recommendations and continue working with experts and stakeholders to develop the framework for the safe and effective adoption of Wolbachia technology. It also noted that the panel said the implementation of new tools should not preclude continuation of the ongoing surveillance and mosquito control efforts.

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.”

Singapore is in the middle of a dengue epidemic, with 16,263 dengue cases this year so far. More than 22,000 cases were reported last year.

Jurong West on dengue alert after 12 new cases in two weeks
Channel NewsAsia 29 Oct 14;

SINGAPORE: In just the past two weeks, 12 new dengue cases have been reported at Jurong West Street 52 and Corporation Road.

This brings the total number of cases there to 36 - making it the biggest dengue cluster.

As of last Friday (Oct 17), 26 cases were reported at Jurong West Street 52, of which 14 came from Block 518. Ten more cases were reported at Corporation Road.

Some residents suspect that an abandoned police station in the vicinity could have become a mosquito breeding ground. "There are a lot of weeds growing in the drain next to the carpark and I believe it's waterlogged but we have no way of getting in to take a look. So, I hope the relevant authorities will come and clear it," said a resident.

Residents also expressed their concern over the rise in the number of cases.

- CNA/ec