On The Trail Of A Mosquito Hunter

Challenge follows Vector Control Officer Chua Hong Eng to find out how she stops mosquitoes from breeding in a neighbourhood.
Six days a week, 62-year-old Chua Hong Eng, a Vector Control Officer from the National Environment Agency (NEA), combs through private estates in Bukit Timah for potential mosquito breeding sites. She covers one of the six areas that she is in-charge of every day.
Mdm Chua’s day starts at 6.30am with a 25-minute cycle from her home to an NEA bin centre at Block 4, Toh Yi Drive. This is where she collects her equipment before she cycles to one of the private estates to start work.
After parking her bicycle, Mdm Chua puts on gloves to protect her hands before starting her inspection on foot.
Mdm Chua keeps her eyes peeled for stagnant water, which is a potential breeding ground for mosquitoes. She inspects every nook and cranny of the neighbourhood, even lifting the lids of every dust bin she passes by.
When Mdm Chua finds any stagnant water, she inspects it for any pre-adult mosquitoes (larvae or pupae). For out of reach places such as drains, she scoops some water out for a closer look. The innovative officer, who enjoys collecting items to make her own tools, created this long scoop by combining the extendable handle of a paint roller with a ladle.
If Mdm Chua does not spot any signs of life in the water, she sprays a layer of anti-malarial oil that prevents mosquitoes from laying their eggs.
Mdm Chua pulls a trolley, which she has modified to carry the metal can containing over four litres of anti-malarial oil.
Mdm Chua makes a sudden stop along Eng Kong Drive when she spots this potted plant. A layer of water pools on top of the pot’s hardened soil. She removes some of the water with her scoop for a closer look.
Larvae wriggle just beneath the surface of the water. If these larvae are not destroyed, they will develop adult mosquitoes soon. Mdm Chua shares that potted plants are one of the most common mosquito breeding spots.
Mdm Chua keys the location of the breeding spot into NEA’s vector control information database using her office-issued PDA. She learnt how to use the PDA after training by the NEA. The self-motivated officer isn’t daunted by technology; outside of work, she has signed up for computer lessons on her own accord.
After walking for more than three hours, Mdm Chua takes a short rest. She chats with a co-worker fluently in Malay – a language that she picked up over the years by interacting with her colleagues, most of whom are Malay.
After seven years on the job, the officer has become extremely sharp-eyed. She does not miss this small opening at the bottom of a broken fence. She proves that there is water inside by sticking a branch into the hole – it comes out moist. She then sprays the anti-malarial oil into the hole.
Instead of pouring away the infested water, the officers add some sand granular insecticide into the water to kill all the larvae and pupae present. This will keep the pot mosquito-free for at least a month. The officers also advise the owner to discard this pot to prevent the infestation from reoccurring. Mdm Chua continues on her search on foot.
Mdm Chua’s supervisors, Mr Rosli Bin Ali (left) and Mr Ho Keng Wee (right), are alerted and they arrive at the location to talk to the homeowner after inspecting the infested waters. The supervisors, who are trained to handle such situations, issue the homeowner a warning letter and also bring a sample of the pre-adult mosquitoes back to their office.
As Mdm Chua continues on her search, she looks out for water collected in discarded canvas sheets, which are another common breeding ground. The hardworking officer also looks out for rat holes even though that is not part of her job.
Mdm Chua ventures into overgrown grass patches in search of stagnant water. She never loses her footing, despite the uneven ground which is covered with a thick layer of fallen leaves. She keeps a look out for water trapped in the plants, for example in tree hollows. Although she does not spot any water in the holes, she sprays some anti-malarial oil as a precaution.
Mdm Chua opens the drain cover so that she can inspect the drain water below. Stagnant water can sometimes be found in the drains, for example, when leaves accumulate and create blockages.
Mdm Chua does not find her job tough, despite having to walk for six hours – often under the hot sun and occasionally in the rain. “I like that I can enjoy the sunshine and exercise,” says the energetic officer, who dislikes working in air-conditioned places.
After covering the area she needs to inspect, Mdm Chua returns her equipment to the bin centre at 2pm and heads home to rest. The active officer does not plan to retire any time soon. “There’s nothing to do at home but stare at the walls!”
    Sep 10, 2013
    Tay Qiao Wei
    John Heng
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