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Frontline fighters in the mosquito wars

Frontline fighters in the mosquito wars
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First Published: Tue, Sep 07 2010. 11 44 PM IST
New Delhi: The only way to destroy the mosquito is to make it breed,” declares E.C. Thomas, film-maker, amateur scientist and the inventor of a quirky contraption that uses a combination of a suitcase-sized water tank and a system of ingenious, but elementary valves and siphons to trap mosquito larvae.
Though Thomas’ device, christened “Take it Eazzy” as a play on his name, is still a prototype, he’s part of a disorganized global league of researchers and manufacturers exploring ingenious alternatives against the insect and the diseases it spreads, such as the current dengue outbreak in the national capital.
Also See Ingenious Devices (Graphic)
Unlike traditional research that focuses on drugs and vaccines, this band of mosquito baiters rely on a variety of approaches, from mosquito magnets and mosquito traps, that try to exploit everything from genetics to mosquito psychology. This includes their fear of bats and dragonflies, dependence on human blood, and a compulsion to breed rapidly.
In February, scientists at the University of California, Irvine, Oxford University and Oxitec Ltd, a medical firm, reported in the Proceedings of the National Academy of Sciences of being able to create “wingless” mosquitoes that were genetically engineered to have weak muscles. No-fly mosquitoes, they reasoned, would be unable to travel and spread disease.
An Auckland-based manufacturer has developed a commercial product that uses a combination of synthetic chemicals and light displays to lure mosquitoes into a trap—a high-speed fan that sweeps the mosquito into a special bag where they choke and die.
The Sunbeam Electronic Mosquito Repeller, made by a Californian company, emits ultrasonic sound waves, mimicking the dragonfly—the insect’s key nemesis—and thereby keeping mosquitoes away.
American Biophysics Corp. makes mosquito magnets that work by emitting a steady stream of carbon dioxide, heat, moisture and octenol. The carbon dioxide fools the mosquito into assuming a human being is around and lured within range, is sucked in by the magnet, which dehydrates and thus kills the pest.
Thomas’ machine relies on what he calls the mosquito’s biggest weak point—the need to breed. It consists chiefly of a steady supply of 10 litres of water in a rectangular basin.
“Think of the water tank as a high-end bar,” Thomas explains enthusiastically. “The female mosquito is desperate for any source of still water—water coolers, ruptured rubber tyres. So the tank looks most inviting and, to the mosquito, the best place to lay its eggs.”
The tank has a vent at the bottom that opens every 10 days, the time typically taken for larvae to hatch. This drains out the eggs into another tank containing pebbles, salt and sand, which kills the larvae. The vent opens and closes by siphon effect.
“The chambers are designed such that even if some larvae do hatch into mosquitoes, they are trapped. There’s no outlet. The tanks are kept dry through evaporation. So there’s no external energy required to keep the cycle going,” Thomas said.
The system is most effective in regions with substantial mosquito infestation. In preliminary tests in his yard in Alapuzha district of Kerala—known for regular chikungunya outbreaks —there was a marked decline, he said, in mosquitoes over three years.
“It’s not a quick fix solution. But given a sufficient number of tanks spread out over several places, you will certainly see a noticeable decline,” said Thomas, who is scheduled to meet health minister Ghulam Nabi Azad later this month for a demonstration and thereafter possible funding.
Experts say his idea is conceptually sound, but will need more tests before being validated.
A.P. Dash, former director of Delhi-based National Institute of Malarial Research, said any approach to address the mosquito problem was welcome.
“Several organizations as well as individuals are trying out a variety of devices,” he said. “But these devices need years of testing. However, it’s time that we moved beyond drugs and vaccines to curb mosquitoes.”
According to the World Health Organization, mosquitoes are estimated to infect more than 700 million people annually in Africa, South America, Central America, Mexico and much of Asia, with at least two million dying every year from such diseases.
India has about a million cases of malaria every year, with about 1,000 deaths. And Delhi, with above average rainfall this year and construction work related to the Commonwealth Games, has reported over 1,300 dengue cases—among the highest in the last five years—and four deaths due to the mosquito-borne disease.
C.R. Pillai, an emeritus professor with the Indian Council of Medical Research, said mechanical approaches cannot be a stand-alone solution.
“The aedes larvae (the dengue carrier) can survive longer than the anopheles (carrier of malaria) and only needs a bit of moisture. No device can beat evolution. You have to target parasites as well as the carriers,” he said.
Photo by Pradeep Gaur; graphic by Ahmed Raza Khan/Mint
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First Published: Tue, Sep 07 2010. 11 44 PM IST