We thank Mr Chee Chi Weng for his feedback ("Further steps to cut mosquito population"; last Saturday).

The National Environment Agency (NEA) regularly explores new tools and technologies to improve dengue control in Singapore.

Today, besides conducting checks for breeding habitats based on dengue cases, we also take a preventive and risk-based approach through pre-emptive checks in areas assessed to be at higher risk, even in the absence of dengue cases.

These preventive checks aim to eradicate mosquito-breeding habitats (source reduction) and suppress the mosquito population to as low a level as possible, such that disease transmission cannot be sustained.

We are already making evening inspection calls in areas where there is active dengue transmission, to ensure that all premises are inspected in a timely manner.

The primary mosquito vector that spreads dengue, the Aedes aegypti, breeds in artificial water-bearing receptacles such as roof gutters, concrete drains and commonly found domestic containers like vases, pails and pot plates.

Aedes aegypti mosquitoes typically do not breed in more natural settings such as rivers, forested areas or wetlands.

Hence, efforts should be focused on artificial water-bearing containers in urban areas.

To monitor the mosquito population in cluster and high-risk areas, the NEA deploys Gravitraps, which attract and trap female Aedes mosquitoes that are looking for sites to lay eggs, and which prevent the emergence of any mosquitoes from eggs laid in the traps.

The NEA is also conducting studies on the feasibility of using Wolbachia-carrying male Aedes aegypti mosquitoes, which do not bite, to help suppress the Aedes mosquito population.

Meanwhile, source eradication of mosquito-breeding habitats and the spraying of insecticide to control the adult mosquito population remain critical to dengue prevention.

The NEA cannot eradicate dengue alone. All stakeholders must continue to play their part to help stem dengue transmission in the environment and reduce the mosquito population, by checking their premises daily for potential mosquito-breeding habitats and removing them.

Tony Teo
Director
Environmental Public Health Operations
National Environment Agency