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Why can’t NEA just fog the entire island to kill adult mosquitoes?

The National Environment Agency (NEA) emphasises source reduction of the Aedes mosquito as the primary focus of its dengue control efforts. This is why we encourage all stakeholders to regularly check their premises for potential mosquito breeding habitats. Inverting pails and plant pot plates, and changing water in vases regularly when they are not in use, are simple steps that all of us can take daily to prevent mosquitoes from establishing a foothold in our neighbourhoods.

At dengue cluster areas, NEA carries out vector control operations to remove mosquito breeding habitats, and conducts indoor spraying/misting of insecticides and outdoor fogging to kill adult mosquitoes, and oiling of stagnant water (e.g. in drains) to kill mosquito larvae and pupae. In such areas with active transmission, outdoor fogging and indoor spraying, misting are both necessary, because there may be infected adult mosquitoes in both outdoor and indoor areas that need to be destroyed, before they bite and infect more people. These methods are, however, only effective if the chemical has direct contact with the mosquitoes, and thus have to be repeated frequently as new batches of mosquitoes will continue to emerge until all mosquito breeding habitats are found and removed. Fogging should also be carried out in the earlier part of the morning or later part of the afternoon, when Aedes mosquitoes are known to be most active. This is because ambient temperatures during these times are lower, so the fog can stay at ground level longer, optimising insecticide contact with mosquitoes. Given these considerations, routine fogging is not a sustainable vector control measure - source reduction is still a more effective and sustainable strategy.

For non-dengue-cluster areas, the most effective mosquito control measure for keeping the mosquito population low is still source reduction, through detecting and removing mosquito breeding habitats and killing larvae/pupae, as this eliminates the mosquitoes at the most vulnerable stage of their life cycle. This is in line with the World Health Organization’s (WHO) recommendations for vector control.

It is therefore important that owners of premises regularly undertake vector control measures, and ensure proper housekeeping within their premises at all times, to remove potential mosquito breeding habitats. Residents also need to do their part to prevent mosquito breeding in their homes by doing the Mozzie Wipeout. When indoor misting has to be conducted, infants, the elderly, pregnant women and those with respiratory problems, are asked to leave the premises before the commencement of indoor misting, and allowed to re-enter only 10 minutes after misting has been completed. Pet owners will also be asked to keep their pets outside the premises and cover their aquariums, as well as cover food and utensils that may be exposed during any fogging or misting operations. When outdoor fogging or misting is being conducted, residents are advised to close their windows and remain indoors, and cover their food and utensils.

When the use of fogging and misting is necessary, residents will be informed in advance. If fogging is carried out at HDB blocks, a notice will be put up at the block’s notice boards. If it is carried out at landed properties, individual notices will be sent to the properties. For fogging carried out by private entities (e.g. managing agents of condominiums, residents of landed properties, etc.), residents will be notified by the Pest Control Operator (PCO) employed by the respective entities.

Posted on 12 May 2016 02:30 AM