The role of human odours in host location of female Aedes aegypti (Diptera: Culicidae)

Eiras, Alvaro Eduardo (1991) The role of human odours in host location of female Aedes aegypti (Diptera: Culicidae). University of Southampton, Doctoral Thesis.

Abstract

The behavioural responses of female A.aegypti to carbon dioxide, lactic acid and human odour extract were investigated using a behaviourally discriminating wind tunnel bioassay. The take-off, upwind flight, landing and probing responses of the mosquitoes were recorded using direct observation and video techniques.

Carbon dioxide elicited the complete sequence from activation to landing behaviour. A threshold carbon dioxide concentration for taking-off of approximately 0.01% above the ambient level was detected. Upwind flight pattern varied with carbon dioxide concentration, straight flights tended to occur in low concentrations whereas zig-zagging occurred in high concentrations. Lactic acid and sweat extract did not activate mosquito to fly upwind when presented alone, however, when combined with carbon dioxide take-off was enhanced. Lactic acid elicited landings on the point source of carbon dioxide only within a window of low to intermediate concentrations. Sweat extract elicited landings in the absence of carbon dioxide. This indicated the presence of chemical stimuli, other than lactic acid, active in the close range.

Probing behaviour occurred only when carbon dioxide stimuli were presented, the addition of lactic acid or sweat extract enhanced the probing activity.

Mosquitoes orientation in the long and short ranges to the host were investigated using contrasting odour plumes. In the long range, mosquitoes were activated to fly by a combination of carbon dioxide and human odour; in the close-range, they switch to landing behaviour primarily guided by the plume of human odour. In the long range, lactic acid decreased the threshold for behavioural response whereas in the close range, in low concentrations, it had no effect and high concentrations inhibited landing on a point source of carbon dioxide.

Mosquitoes responded significantly to combined convection currents and water vapour produced by human hands in an olfactometer bioassay. The addition of lactic acid to water vapour and convection currents did not enhance mosquito responses. Sweat extract and convection currents elicited significantly higher responses than other stimuli, suggesting the presence of active chemicals, other than lactic acid in human sweat.

This record has no associated files available for download.

Contributors

Download statistics