The response of the malaria mosquito, Anopheles gambiae, to two components of human sweat, ammonia and l‐lactic acid, in an olfactometer

Abstract

SummaryIn an olfactometer study on the response of the anthropophilic malaria mosquito Anopheles gambiae s.s. (Diptera, Culicidae) to human sweat it was found that freshly collected sweat, mostly of eccrine origin, was attractive, but that incubated sweat was significantly more attractive than fresh sweat. The behavioural response to l‐lactic acid and ammonia, the main constituents of sweat, was investigated. l‐lactic acid was attractive at one concentration only (11.11 mm) and removal of the l‐lactic acid from the sweat by enzymatic decomposition did not affect the attractiveness of sweat. Ammonia caused attraction over a range of 0.1–13.4 m on glass slides and at 0.84–8.40 μmol/min in an air stream. It is concluded that: human sweat contains kairomones for host‐seeking An. gambiae; ammonia is an important kairomone for this mosquito; and that l‐lactic acid is not a prerequisite in the attraction of An. gambiae to sweat.

Olfaction in vector-host interactions

“…Ammonia elicits excitatory responses in all functional types of grooved peg sensilla and some types of sensilla trichodea in An. gambiae (Meijerink et al 2001, Qiu et al 2006, which finding nicely correlates with the reliable attraction of female An. gambiae to sources of this compound (Braks et al 2001.…”

“…gambiae (Meijerink et al 2001, Qiu et al 2006, which finding nicely correlates with the reliable attraction of female An. gambiae to sources of this compound (Braks et al 2001. Lactic acid has a similar behavioural effect on female Ae.…”

“…More recently several important studies have begun to unravel the olfactory physiology of An. gambiae antennae (Meijerink et al 2001, Meijerink and van Loon 1999, Qiu et al 2006. At the same time there is a growing appreciation of the antennal expression patterns of several genes that encode signal transduction components that have been linked in one degree or another to…”

“…gambiae contained at least one neuron that responded to ammonia and 1-butylamine. ORNs in GP sensilla were found responding to oxocarboxylic acids, short-chain carboxylic acids and lactic acid, compounds that are shown to attract mosquitoes or to enhance landing responses (Braks et al 2001, Healy and Copland 2000, Knols et al 1997.…”

“…L-lactic acid, short-chain fatty acids and ammonia are attractive for Aedes and Anopheles (e.g. , Braks et al 2001. Carboxylic acids, alcohols and aldehydes are attractive for Culex .…”