Biological, chemical methods to wipe out mosquitoes
By Maria Almenoar, Straits Times 10 Jun 09;
THE search-and-destroy mission against mosquitoes in malaria-hit Sungei Kadut and Jurong Island is in full swing.
To stop the illness from spreading beyond the 15 cases so far, the National Environment Agency (NEA) has deployed 50 officers to look for and destroy breeding sites in the forested areas of Sungei Kadut in the north and Jurong Island in the south-west.
The breeding spots in Sungei Kadut are sprayed with bacteria in the morning to kill mosquito larvae.
To target adult mosquitoes, chemical fogging is done there at night. This stepped-up enforcement is likely to continue for three weeks or until no more cases are reported.
So far, NEA has identified three types of Anopheles mosquitoes in these areas.
The mystery, however, lies in the fact that two of the three types are not associated with spreading malaria, while the remaining type has been linked to the spread of malaria in China and Korea, but not here.
The Health Ministry said it is still investigating how the disease has surfaced here - especially since the 15 people infected in the past five weeks had not travelled recently, so they could not have brought the disease in from abroad.
The latest case was reported on Monday.
Of the 15 patients, 14 were foreign workers, and one, a full-time national serviceman. All have since been discharged from hospital.
The more than 20 foreign worker dormitories in the Sungei Kadut/Mandai area have been directed by NEA to carry out residual spraying on both the inside and the outside surfaces of the buildings. Dormitory operators have also given mosquito netting and insect repellent for distribution to foreign workers.
Malaria is distinguished from the other two mosquito-borne diseases chikungunya and dengue in that it is transmitted by the Anopheles mosquito; the other two diseases are caused by the Aedes mosquito.
The Anopheles mosquito is active at night and found in forest areas or brackish water, while the Aedes mosquito tends to be active in the day and is found near where humans live.
NEA is stepping up operations in malaria-affected clusters in Singapore
Lian Cheong/Lynda, Channel NewsAsia 9 Jun 09;
SINGAPORE: The National Environment Agency is stepping up operations to deal with two malaria clusters in Sungei Kadut and Jurong Island.
50 NEA officers are conducting daily checks in the affected areas.
They conduct light trapping of the Anopheles mosquitoes after fogging has been carried out.
Although pest busters do not recommend fogging as a long-term measure to control mosquitoes, the World Health Organisation recommended it for destroying malaria-infected adult mosquitoes.
Tai Ji Choong, Head of Operations, Environmental Health Department, NEA, said: "You must use the right chemicals for fogging. With the right chemicals, fogging is still an effective mosquito control operation.
"It depends on what the situation is. In the case of malaria control, fogging is definitely a necessary control measure." - CNA/vm
Foreign worker dorm in Sungei Kadut checked regularly for mosquitoes
Tyler Thia and Lynda Homg, Channel NewsAsia 9 Jun 09;
SINGAPORE : A foreign worker dormitory in Sungei Kadut, which houses about 400 foreign workers, conducts checks regularly for mosquitoes.
The Sungei Kadut and Mandai area recently saw 9 people contracting malaria.
The dorm also checks the drains for larvae, and fogging is conducted regularly.
Pest busters said fogging may not be the most effective way of getting rid of mosquitoes although it is the cheapest way to do so.
Fogging can also destroy other flying insects like dragonflies, which can prevent the spread of mosquitoes. - CNA /ls
Three mosquito species, only one is a suspect
Pests not known to have spread disease here but have done so in China, S Korea
Today Online 10 Jun 09;
THREE species of the Anopheles mosquito have been found breeding in the recent malaria clusters - one of which is a known malaria vector, or agent, in China and South Korea.
The National Environment Agency (NEA) said the Anopheles sinensis is not known to have caused malaria in Singapore, and investigations are still in progress to determine if it caused the latest outbreak.
The other two species discovered do not transmit malaria.
Fourteen cases of suspected local malaria transmission were discovered last month in the Mandai-Sungei Kadut area and Jurong Island - the largest local outbreak in years. None of the patients had been abroad recently.
Operations to destroy mosquito breeding grounds began at the end of last month, and will continue for at least three more weeks.
Up to 50 officers have been deployed daily to the two clusters to conduct search-and-destroy operations, said NEA’s head of operations for the Environmental Health Department Tai Ji Choong.
“We are conducting very aggressive night fogging, to destroy any adult Anopheles mosquitos. We also conduct adult mosquito trapping, to determine the effectiveness of our fogging operations,” he told reporters at the edge of a forest in Sungei Kadut yesterday where operations were underway.
“At the same time, (it is) also to determine what are the species of Anopheles that could be responsible for the outbreak.”
The Anopheles sinensis mosquito breeds in still water and partial sunlight, making the Sungei Kadut forest an ideal location.
With a potential flight range of up to 1km, the foreign worker dormitories and military training camps in the vicinity are at risk of infection.
One of those who suffering from malaria recently was a National Serviceman while the rest were foreign workers.
Dormitory operators have also been told to conduct their own periodic fogging and spraying of insecticide.
The last outbreak of suspected local malaria transmission in Singapore was reported on Jurong Island in 2006, although there are an average of 200 imported cases a year.
Singapore was certified malaria-free by the World Health Organization in 1982, a status granted to countries who have no sustained local transmissions for three consecutive years.
The NEA also has a malaria control programme islandwide which identifies areas that are conducive for mosquito breeding.
The agency’s officers conduct monthly checks on these places to locate and destroy the breeding habitats. 938LIVE
