Science - June 3, 2010

Malaria mosquito prefers smelly socks to aroma traps

A mixture of ammonia, lactic acid, and twelve fatty acids can lure malaria mosquitoes into the trap. However, given a choice, the mosquitoes would go for the odour of human sweat, reported Wageningen entomologists last month in the Journal of Medical Entomology.

Aroma traps work well, as shown by experiments; catching mosquitoes during a night in Gambia.
Postdoctoral student Renate Smallegange carried out research into the mosquito Anopheles gambiae Giles sensu stricto, a major transmitter of malaria in Africa. 'This mosquito has a penchant for human blood and goes in search of victims especially at night.' Research done by Bart Knols and Marieta Braks has clearly shown that artificial substances such as ammonia, lactic acid and particular types of fatty acids are able to lure the mosquito. Smallegange herself has already proven that a combination of these odour substances works even better. She has now evaluated how well this mixture performs as compared to our sweaty socks.
Aroma profile
The mosquitoes obviously found the sweaty foot odour more attractive than the artificial stuff, she concludes. 'We are still short of some essential stuff in our aroma mixture. Humans seem to have something very specific in their aroma profile.' She does not yet know what these aroma substances are. 'Our sweat comprises more than three hundred aroma substances. We want to make some selections now to find out which of these aroma substances can be perceived by the mosquito. We have also compared attractive sweat with less attractive sweat, but the differences in the composition of our sweat are small.' The ideal malaria perfume has not been discovered yet.
Field experiments
With the aim of luring mosquitoes into the trap with an effective aroma mixture, Wageningen entomologists are carrying out field experiments in Kenya, Tanzania and Gambia to find the best aroma substances and the best locations to place these. 'The experiments show that we can also hang the traps outdoors to divert mosquitoes', says Smallegange. Besides aroma traps, other eradication measures are needed to reduce the number of malaria victims in Africa, she says. Current measures include vaccination against malaria, the use of mosquito nets and biological eradication of mosquitoes using moulds.

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