MALARIA: Attracting mosquitoes by smell

28 Jul, 2010
With around half the world’s population at risk of malaria, researchers have put a lot of effort into finding ways to prevent infection. Interventions commonly focus on preventing bites from the mosquitoes that transmit the malaria parasite using, for example, insecticide-treated bednets.
However, researchers at the Ifakara Health Institute in Tanzania are working on a more unusual method – traps that mimic the scent of humans.
Mosquitoes find their prey mostly by smell, and are attracted to compounds found in sweat, body odour and breath. A hunting mosquito can smell a human from about 30 metres away.
The research team created a synthetic blend of compounds such as carbon dioxide and ammonia that have been shown to draw mosquitoes to humans. They optimised the amount of each compound to make the blend as attractive as possible to mosquitoes over long ranges.
Some synthetic lures already exist, but this is the first time that they have been tested outside of a laboratory setting. The researchers tested their lure in a rural village, attaching it to a large screened cage. They then put this in a hut and compared the number of mosquitoes they trapped with those caught in traps in a nearby hut containing no lure but human volunteers (note, no humans were intentionally put in harm’s way for this experiment!).
The researchers found that the lure attracted 3-5 times more mosquitoes than the human volunteers when placed in a separate hut over 10 metres away. It was equally or less attractive when contained within the same hut, suggesting that the lure would be most effective for long-range use.
The potential benefits of these lures are impressive. In their latest paper, the researchers’ suggests that such traps should be used strategically in places where mosquitoes are prolific, such as near larval breeding sites, in addition to insecticide-treated bednets and other existing methods.
They conclude that 20-130 traps used in a group of 1000 people would reduce malaria transmission by 99 per cent or more in most areas. If developers can optimise the lures further and make the traps as cheaply as possible, this could make a real impact on the fight against malaria in the developing world.
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