NEA to test using Wolbachia bacteria-carrying mosquitoes in fight against dengue

The small-scale field study will involve the release of male Wolbachia-Aedes mosquitoes at a few selected sites at the end of the year.
Channel NewsAsia 12 Apr 16;

SINGAPORE: Bacteria-carrying mosquitoes will be released at a few selected sites at the end of 2016 in a bid to suppress the Aedes aegypti mosquito population responsible for transmitting the dengue virus, said the Ministry of Environment and Water Resources (MEWR) on Tuesday (April 12).

The National Environment Agency (NEA) has been conducting a feasibility study to fight dengue by deploying male Aedes mosquitoes carrying the Wolbachia bacteria. When they mate with a female, Wolbachia-free Aedes aegypti mosquito, the eggs they produce will not hatch.

NEA said the upcoming small-scale study aims to understand the behaviour of Wolbachia-Aedes mosquitoes in an urban built-up environment, such as their longevity and flight range. This data collected will support the design of a subsequent suppression trial.

This comes against the backdrop of 6,338 dengue cases reported in the first quarter of 2016, nearly triple the amount reported for the same period in 2015. NEA previously said that the number of dengue cases in 2016 may exceed 30,000, above the record 22,170 reported in 2013.

NO PUBLIC RISK

NEA has assured the public that the male mosquitoes do not bite and hence the release of the Wolbachia-Aedes will not pose any risk of biting or disease transmission.

“We are not embarking on this lightly,” Minister for Environment and Water Resources Masagos Zulkifli told Parliament during the Committee of Supply debates on Tuesday. “We have studied this for years and have taken all steps to ensure public health and safety will not be compromised. Our comprehensive risk assessment has concurred with previous findings on the safety of this technology. We will engage residents and stakeholders to provide more information on the technology and the study in due course.”

NEA also appointed a research company in October last year to conduct an independent assessment, due to be completed in July, to identify any potential secondary environmental and social impact that may arise from the implementation of the technology. The review will also identify appropriate mitigation and monitoring measures, to minimise and forewarn of any possible secondary consequences before, during and after implementation, said NEA.

CONTINUING PREVENTION EFFORTS

NEA also noted that in March this year there was a 30 per cent reduction in mosquito population, and an associated reduction in the weekly number of dengue cases. Nonetheless, Mr Masagos said: “The recent decrease in cases does not mean that we are safe. Similar to past years, cases may increase as we enter the traditional dengue season in June.”

Source eradication of mosquito breeding habitats and spraying of insecticides to control the adult mosquito population remains the key to dengue prevention, said NEA.

The agency said it had conducted some 350,000 inspections islandwide this year, as of March 31, and uncovered about 4,200 instances of mosquito breeding habitats. More than 20 Stop Work Orders and 120 Notices to Attend Court have been issued to construction site contractors for mosquito breeding, with over 10 court prosecutions dealt out for repeat offences.

As of March 14, NEA has also extended its enforcement regime to all residences found with mosquito breeding, regardless of whether they are within or outside dengue cluster. From January to March this year, over 470 households were fined for breeding mosquitoes.

- CNA/jo

NEA to deploy bacteria-infected mosquitoes in fight against dengue
SIAU MING EN Today Online 12 Apr 16;

SINGAPORE — Male Aedes mosquitoes infected with a naturally-occurring bacteria that causes dud eggs when they mate will be released at a few selected sites at the end of this year in the first field study in Singapore on this biological control method’s effectiveness in suppressing the mosquito population.

Minister for the Environment and Water Resources Masagos Zulkifli announced the six-month study on Tuesday (April 12), which aims to get a clearer picture of how these Wolbachia-carrying mosquitoes survive in Singapore’s urban built-up environment and their vertical and horizontal flight range in the open environment.

Only male mosquitoes will be released for the study and as they do not bite, there is no risk of biting or disease transmission, said the National Environment Agency in a press release. Wolbachia is a naturally-occurring bacteria found in over 60 per cent of insect species, including butterflies, fruit flies, dragonflies, and certain mosquito species. The bacteria is, however, not found in the dengue-carrying Aedes aegypti mosquito.

Speaking during the debate on his ministry’s budget on Tuesday, Mr Masagos said, without disclosing the test locations: “We are not embarking on this lightly. We have studied this for years and have taken all steps to ensure that public health and safety will not be compromised.”

Nevertheless, a research company was appointed to carry out an independent assessment on whether the biological control method will pose any potential secondary environmental and social impact, and how to minimise these consequences. The study will conclude in July this year.

Injecting male Aedes with Wolbachia and releasing them as a way to suppress the species’ population has been around since the 1960s and has been tested in various countries, including Vietnam, Indonesia, Australia, and Brazil.

When an infected male mates with a female, the eggs do not hatch.

In Singapore, the authorities first announced it was considering the method in June 2014 and have so far conducted feasibility tests in laboratories, but not in the field.

Mr Masagos said his ministry will engage residents and stakeholders to provide more information on the technology and study in due course.

The field study comes in the wake of a warning issued by the authorities in February that Singapore could have a historic high of 30,000 dengue cases this year because of the ongoing El Nino phenomenon, along with a change in the type of dengue virus circulating among Singapore’s population. The previous record was 22,170 dengue cases in 2013.

In the first three months this year, there were 6,338 dengue cases, which is more than double that during the same period last year. Although there was a 30 per cent reduction in mosquito population last month, leading to an associated reduction in the weekly number of dengue cases, Mr Masagos cautioned that Singapore is not in the clear, warning that the number of cases may yet climb during the traditional dengue season in June.

Among other efforts to tackle dengue, the NEA will train 5,000 more Dengue Prevention Volunteers this year, to nearly double the pool of 5,800 such individuals tasked with educating the public on riding breeding sites. The additional volunteers can boost house visit efforts, especially in yellow and red dengue cluster areas. Another 250 temporary officers will also be engaged by the NEA this year to carry out inspections islandwide.

Field study to assess using special mozzies against dengue
Carolyn Khew, The Straits Times AsiaOne 13 Apr 16;

A field study will be conducted at the end of this year to assess if a special type of mosquito can be a weapon against dengue.

The male Wolbachia-carrying Aedes aegypti mosquitoes will be released into the environment in the small-scale study to be conducted by the National Environment Agency (NEA).

Speaking during the debate on the ministry's budget, Environment and Water Resources Minister Masagos Zulkifli said the Government was not embarking on the study "lightly", and had "studied this for years and taken all steps to ensure that public health and safety will not be compromised".

Only male mosquitoes, which do not bite, will be released.

Wolbachia is a naturally occurring bacteria that can be found in over 60 per cent of insect species, but not in dengue-carrying Aedes aegypti mosquitoes.

When male mosquitoes carrying the bacteria mate with wild female mosquitoes, they produce eggs that do not hatch. This could help to suppress the number of Aedes aegypti mosquitoes in the long run. The method has been used in the fight against dengue in countries such as Australia and Brazil.

The study will look at the behaviour of these special mosquitoes in the built-up environment, such as how long they can live in the wild and their flight range. The data collected will help in the design of a future trial. Previously, studies were conducted in the laboratory by the Environmental Health Institute under the NEA.

Based on the NEA's assessment so far, the technology poses no or insignificant risk of negative impact on public health or ecology.

The NEA has appointed a research firm to identify any potential secondary environmental and social impact that may arise.

Dengue expert Tikki Pang said each country's situation is unique and "only time will tell" if the technology will work in Singapore.

"Any tool that helps in the battle against dengue should be considered and tested," added the visiting professor at the Lee Kuan Yew School of Public Policy at the National University of Singapore.

The announcement comes on the back of a sharp rise in the number of dengue cases this year. A total of 6,338 dengue cases were reported between January and March this year, almost three times as many as the 2,251 cases reported in the same period last year.

The authorities have warned that unless immediate action is taken to suppress the Aedes mosquito population, the number of dengue cases this year may exceed 30,000 - higher than the record set in 2013 when 22,170 cases were reported.

Several MPs also asked about the Government's plan to approve the dengue vaccine for use here.

Mr Masagos replied that it has been closely tracking the development of the vaccine. But as the vaccine is new, "we do not know yet whether its quality is what (the manufacturer) promised it to be".

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