A search for components in human body odour that attract females of Aedes aegypti.

In a new type of wind tunnel, mosquitoes fly upwind towards host odour sources and towards human skin wash extracts obtained by rubbing the skin with a pad soaked in ethanol. We used this behavioural response as a bioassay to identify attractants in liquid chromatography fractions of such extracts. L-Lactic acid is a major constituent of skin wash extracts and it is a necessary component for the extract's effectiveness. As a single stimulus, however, L-lactic acid is only slightly effective. This indicates that the extract's high degree of effectiveness is based on a synergism of L-lactic acid and other odour components. The separation of the extract by liquid chromatography revealed three distinct regions of active fractions, only one of which contained L-lactic acid. The components of the other two regions have not yet been determined. A combination of fractions in these two regions together with L-lactic acid is as attractive as the complete extract.