Singapore: Aedes mosquitoes immune to some insecticides

Lim Wee Leng Channel NewsAsia 5 May 13;

SINGAPORE: The Environmental Health Institute (EHI) has found that in the last 20 over years, the Aedes mosquitoes have developed resistance to certain active ingredients in some insecticides available on the market.

EHI is a public health laboratory at the National Environment Agency (NEA).

Hence the NEA is advocating source reduction as a primary dengue control measure, meaning getting people to remove sources of places of mosquito breeding.

EHI's Dr Christina Liew said: "NEA only uses fogging for disease control measures, in cluster areas when the number of dengue cases is very high. Otherwise, we do not advocate fogging for normal control measures."

Meanwhile, with the number of dengue cases rising to new highs week after week, some people have armed themselves with insect repellent wipes.

Sales of insect screens also rose some 20 per cent.

But environment health experts say the best prevention is to wipe out all mosquito-breeding spots.

Dr Liew said: "The main dengue vector breeds indoors and is found indoors, so the only really effective measure is indoors ULV fogging. What NEA is now advocating is that if you're in a dengue cluster area, you can use aerosol to spray in dark corners of your homes, where the Aedes mosquito hides, such as behind the sofa, behind the curtains, or in the dark corners of your toilet.

"The chemicals that are available on the market do have very high levels of active ingredient, which are still effective against the mosquitoes. So, with targeted spraying, where you focus actually on finding the mosquitoes, these chemicals are still effective."

- CNA/ir