Alternating Chemicals to Prevent Mosquitoes Developing Immunity against Repellents

Mr Yee Chia Hsing asked the Minister for the Environment and Water Resources as mosquitoes may build up their resistance to the same type of chemical being used consistently, whether the alternating of chemicals is currently practised in fogging and, if not, whether the Ministry will review the current practice of fogging.

Source reduction, or eliminating potential mosquito breeding habitats, is the most effective method to reduce the mosquito population. It is much easier to detect and kill mosquitos at the larval stage than to undertake fogging to try to eliminate them after they hatch.

Nonetheless, fogging may still be necessary as a complementary approach when there is urgency to reduce a large mosquito population, such as in areas where there is active dengue transmission. The National Environment Agency (NEA) does not practise the alternating of chemicals used in fogging as a standard procedure. Instead, fogging is carried out in a selective and targeted manner to avoid the build-up of resistance in the mosquito population. As an additional safeguard, NEA regularly monitors the resistance of mosquitoes against insecticides to ensure that the insecticides used are effective.

Fogging is only a small part of the mosquito control strategy. Other actions such as diligently removing any potential sources of mosquito breeding are needed to protect our families from mosquito-borne diseases. I urge everyone to continue to do his part to keep the mosquito population in check.