Human sweat and 2-oxopentanoic acid elicit a landing response from Anopheles gambiae

A wind tunnel bioassay and video to observe mosquitoes landing on heated gl ass cylinders were used to test sweat and some derivatives for responses of Anopheles gambiae Giles (Diptera: Culicidae), a highly anthropophilic Afri can species of malaria vector. Filter papers impregnated with human sweat a nd a diethyl ether extract from the filter papers elicited significantly mo re landings than a water control (P < 0.001). The concentration of lactic a cid in the extract was determined by GLC assay, but bioassays of an equival ent dose of lactic acid (from a commercial supplier) did not elicit landing s. Chemical analysis of the extract by combined GLC/mass spectrometry indic ated the presence of 73 compounds, of which 40 were tentatively identified. The major components of the extract were aliphatic carboxylic acids. An ar tificial blend of 22 carboxylic acids did not elicit landings. Bioassays of 2-oxopentanoic acid elicited significantly more landings (P < 0.001). The possible importance of oxo-carboxylic acids for host-seeking by anthropophi lic mosquitoes is discussed and their use for trapping is suggested.