By Amanda Lee, TODAY, 16 Jun 2014
For the first time, the National Environment Agency (NEA) is considering the use of biological control methods to limit the spread of dengue, by infecting male Aedes mosquitoes with a type of bacteria that results in females producing eggs that do not hatch.
The NEA’s Environmental Health Institute (EHI) has tested the use of the Wolbachia bacteria in the laboratory, but not in the field. A panel of experts has been set up and will convene in August to look into whether the use of the technology — which has been around since the ’60s and is being tested in Vietnam, Indonesia and Australia — is safe.
There was a record 22,170 dengue cases last year. About 7,000 cases have been reported this year, with the traditional peak period — June to October — only beginning.
Announcing the NEA’s plans at the launch of the Do The Mozzie Wipeout campaign yesterday, Second Minister for the Environment and Water Resources, Ms Grace Fu, said the Government had found the Wolbachia method to be interesting and probably applicable. “We are not under any pressure, of course. We want to fight dengue as quickly as we can, but we also want to make sure the study is thorough and safe,” she added.
Wolbachia technology involves infecting Aedes mosquitoes with Wolbachia — a naturally-occurring bacterium found in more than 60 per cent of insect species. When a male Aedes mosquito carrying Wolbachia mates with a female, the eggs produced do not hatch. The aim is to reduce the Aedes population to a level where dengue transmission cannot be sustained.
While the number of dengue cases so far this year is about 25 per cent below that of the same period last year, Ms Fu said this was still too high.
The Dengue Expert Advisory Panel consists of local and foreign experts and is led by epidemiologist and entomologist Professor Duane Gubler, founding director of the Emerging Infectious Diseases Programme at Duke-NUS Graduate Medical School.
Commenting on the Wolbachia method, Prof Gubler said in an email: “The main advantage of this and the other new methods in the pipeline is that they will control the mosquitoes that are breeding in hidden larval habitats that cannot be controlled by current methods.”
Lab studies by the EHI have shown that mosquitoes carrying Wolbachia have lower transmission potential for all dengue serotypes, as well as for the chikungunya virus. Preliminary data has also shown that male Aedes mosquitoes carrying Wolbachia can compete with wild males for female attention.
However, Monash University Dean of Science Scott O’ Neill said although the technology was powerful, releasing only male mosquitoes with the bacteria is not the most effective. Releasing both males and females infected with the bacteria would greatly reduce the ability of resident mosquitoes to transmit dengue between people, he said. He also noted that the approach Singapore was considering could be costly, as it will require continual releases of male mosquitoes to control the wild mosquito population.
Prof Gubler said other new technologies for tackling dengue could become available in the next three to five years. “These include new insecticides, genetically-modified mosquitoes (sterile male release), vaccines, antiviral drugs and therapeutic antibodies. None will likely be totally effective when used in isolation, but all show great promise if used in an integrated and synergistic programme,” he said.
Meanwhile, Ms Fu said the NEA had conducted more than 1.5 million inspections this year and would continue to focus on areas that have higher potential for dengue transmission. As of June 9, the NEA has issued 373 notices to attend court and 34 stop-work orders. There were 16 court prosecutions involving eight contractors.
S'pore may be among first in world to get dengue vaccine
Drug giant Sanofi Pasteur's vaccine likely to be ready by end of 2015
By Linette Lai In Angeles City, The Straits Times, 16 Jun 2014
THE world's first dengue vaccine could be ready by the end of next year, and Singapore may be one of the first countries to get it.
The need could not be greater. Dengue is the fastest spreading vector-borne viral disease, says the World Health Organisation, and is endemic in over 100 countries. Four in 10 people are at risk of getting infected.
And more than two-thirds of the world's dengue cases come from Asia, with South-east Asia being a major contributor.
Drug giant Sanofi Pasteur aims to put its vaccine in markets where it is most needed first, and that includes South-east Asia.
"The overall ambition is first to address the disease where it is most severe," said Dr Guillaume Leroy, who heads the company's dengue vaccine unit.
At the two-day Asean Dengue Summit held in Angeles City in the Philippines over the weekend, Dr Leroy announced the success of an Asian clinical trial to test the vaccine's effectiveness.
After the vaccine candidate was administered, dengue cases in the group of about 10,000 - including participants from Indonesia, Thailand and Malaysia - fell by more than half.
Another trial, involving more than 20,000 people, is currently under way in Latin America.
"We are at a very critical milestone," Dr Leroy said. "By the end of the year, we will have a full analysis of all the results."
The outcome of these latest trials brings Sanofi Pasteur one step closer to a goal which has been more than 20 years in the making.
The company's work on a dengue vaccine has been hampered by the fact that dengue has four different strains. All must be effectively subdued before any vaccine can be counted a success - which is what Sanofi Pasteur says it has managed to do.
The disease is on the rise in the region.
In Singapore, dengue cases hit an all-time high last year, with more than 22,000 cases and seven deaths reported.
Across South-east Asia, there were about 100,000 reported cases in 2000. By 2010, this figure had reached 700,000.
Experts say this figure might be only the tip of the iceberg. "Not all the cases come to the attention of the public health authorities," said health economist Donald Shepard.
The disease tends to be under-reported due to poor surveillance, or because it is misdiagnosed as another condition.
Dr Maria Rosario Capeding, who heads the dengue study group in the Philippines' Research Institute for Tropical Medicine, welcomed the progress made towards a working dengue vaccine.
"The worst thing is the uncertainty of the disease," she said. "As a mother whose son has been ill with dengue, I can tell you that it is the worst nightmare."
As soon as its vaccine is approved for use, Sanofi Pasteur will be able to churn out 100 million doses a year. In 2009 - long before the vaccine neared completion - the company invested in a €350 million (S$593 million) production plant located in France.
"It was a big risk," Dr Leroy said. "But imagine not making the investment, getting the results, and then telling countries they have to wait five more years."