Resident lays better trap for mozzie eggs

A resident living near a former dengue cluster has invented an improved trap for mosquito eggs that requires minimal maintenance and is smart enough to alert users to problems detected.

The trap is based on an existing device that lures mosquitoes to lay eggs in stagnant water. This device, known as the ovitrap, needs close monitoring - the water must be replaced before the eggs hatch. If not, it becomes a mosquito-breeding ground.

The improved trap, invented by Mr Martin Schweiger, a German turned Singapore citizen, has an automated system to purge the water before the pupae turn into mosquitoes and then fill it up again.

It uses sensors and a computer system that would automatically send e-mail alerts when a problem is detected, such as when the trap is clogged with leaves.

"If the ovitrap is not well- maintained, it can turn into a dangerous breeding spot," said Mr Schweiger, 49, who runs a law firm and a home safety firm that develops products such as air cleaners and mosquito traps.

Mr Schweiger came up with the automated system two years ago. He approached Nanyang Polytechnic in March this year to help develop the e-mail alert system.

He has been testing two of his ovitraps at his Siglap Avenue home in the east, which is near Telok Kurau, a former dengue cluster.

The traps, made of concrete and steel, are emptied twice every week, three times a day. Each trap costs a few thousand dollars.

Mr Schweiger has proposed rolling out 10 of his ovitraps at the Singapore Botanic Gardens from next year. The Botanic Gardens, when contacted, would only say that it is exploring the possibility of using the traps on its premises on a trial basis.

Its director, Dr Nigel Taylor, declined to provide details about the trial, as it is at an exploratory stage.

The National Parks Board currently uses biological control agents called Bacillus thuringiensis israelensis (BTI) to manage mosquito breeding, along with selective thermal fogging and mist spraying. BTI agents are also placed in drains to prevent mosquito breeding.

The National Environment Agency (NEA) used to deploy ovitraps in the fight against mosquitoes, but has switched to gravitraps since 2012. Gravitraps are more effective as they trap adult mosquitoes while ovitraps target only mosquito eggs and larvae.

An NEA spokesman said both gravitraps and ovitraps, when deployed properly, can give a "good sensing of the mosquito population in an area".

"However, gravitraps and ovitraps work best when other potential breeding habitats are removed," the spokesman added.

Over 17,600 dengue cases have been reported so far this year, according to the NEA website. There were 212 dengue cases reported in the week ending Dec 6 - 50 cases more than in the previous week. Last year, 22,170 people came down with dengue fever and seven died from it.

Professor Duane Gubler, from the Programme on Emerging Infectious Diseases at Duke-NUS Graduate Medical School, said there are many variations of ovitraps that have been used to monitor Aedes aegypti mosquitoes - which spread dengue fever - since the 1960s.

"Whether this one will be more sensitive can be determined only by comparative studies," he added, referring to Mr Schweiger's invention.

For Mr Schweiger, the traps have worked well so far. "Our neighbours must be wondering why we are the only household that doesn't close our windows at night."

kcarolyn@sph.com.sg

This article was first published on Dec 13, 2014.
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