Medical and Veterinary Entomology (2001) 15, 259-266

C. Costantini, M.A. Birkett, G. Gibson, J. Ziesmann, N.F. Sagnon, H.A. Mohammed, M. Coluzzi and J.A. Pickett (2001)
Electroantennogram and behavioural responses of the malaria vector Anopheles gambiae to human-specific sweat components
Medical and Veterinary Entomology 15 (3), 259-266
Abstract: Afrotropical malaria vectors of the Anopheles gambiae complex (Diptera: Culicidae), particularly An. gambiae sensu stricto, are attracted mainly to human hosts. A major source of human volatile emissions is sweat, from which key human-specific components are the carboxylic acids (E)- and (Z)-3-methyl-2-hexenoic acid and 7-octenoic acid. Electrophysiological studies on the antennae of An. gambiae s.s. showed selective sensitivity to these compounds, with a threshold at 10^-6 g comparable to that of known olfactory stimulants 1-octen-3-ol, p-cresol, isovaleric acid, and lower than threshold sensitivity to l-lactic acid and the synthetic mosquito repellent N,N-diethyltoluamide (DEET). A combination of the acids released at concentrations > 10^-5 g in wind tunnel bioassays significantly reduced the response to CO₂, the major attractant released by human hosts, for strains of An. gambiae s.s. originating from East and West Africa.
Field trials with odour-baited entry traps (OBETs) in Burkina Faso showed that 7-octenoic acid significantly increased (by 1.7-fold) the catch of females of An. gambiae sensu lato (comprising two sibling species: An. arabiensis Patton and An. gambiae s.s.) in OBETs baited with CO₂, whereas combinations of the acids significantly reduced the catch in CO₂-baited traps (by 2.1-fold) and in whole human odour-baited traps (by 1.5-fold). The pure (E) and (Z) geometric isomers of 3-methyl-2-hexenoic acid gave comparable results to the (E/Z) isomer mixture. These results provide the first experimental evidence that human-specific compounds affect the behaviour of highly anthropophilic An. gambiae s.l. mosquitoes. The compounds appear to inhibit the 'upwind flight' response to known long-range attractants, and may serve either to 'mask' the attractants present or, more probably, to 'arrest' upwind flight when mosquitoes arrive at a host under natural conditions. In the final approach to hosts, vectors are known to reduce their flight speed and increase their turning rate, to avoid overshooting the source. In our experimental apparatus, these changes in flight behaviour would reduce the number of mosquitoes entering the ports of the collection devices.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Carlo Costantini, John A. Pickett, Michael A. Birkett

Research topic(s) for pests/diseases/weeds:
pheromones/attractants/traps

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Anopheles gambiae		Burkina Faso
	Anopheles arabiensis		Burkina Faso