Behavioral response of the malaria mosquito,Anopheles gambiae, to human sweat inoculated with axilla bacteria and to volatiles composing human axillary odor

Abstract

The responses of Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) to odors from male and female axillary sweat incubated with human axilla bacteria were recorded in a dual-choice olfactometer. Staphylococcus epidermidis was selected for its low odor-producing pattern, Corynebacterium jeikeium for its strong Nα-acylglutamine aminoacylase activity liberating carboxylic acids including (R)/(S)-3-hydroxy-3-methylhexanoic acid (HMHA) and Staphylococcus haemolyticus for its capacity to liberate sulfur-containing compounds including (R/S)-3-methyl-3-sulfanylhexan-1-ol (MSH). Anopheles gambiae behavioral responses were evaluated under (i) its responsiveness to take off and undertake sustained upwind flight and (ii) its discriminating capacity between the two olfactometer arms bearing a test odor in either one or both arms. Experiments were conducted in the presence of carbon dioxide pulses as a behavioral sensitizer. Anopheles gambiae clearly discriminated for the olfactometer arm conveying odor generated by incubating any of the three bacteria species with either male or female sweat. Whereas An. gambiae did not discriminate between male and female sterile sweat samples in the olfactometer, the mosquito consistently showed a preference for male sweat over female sweat incubated with the same bacterium, independent of the species used as inoculum. Sweat incubated with C. jeikeium rendered mosquitoes particularly responsive and this substrate elicited the strongest preference for male over female sweat. Tested on their own, neither HMHA nor MSH elicited a clear discriminating response but did affect mosquito responsiveness. These findings serve as a basis for further research on the odor-mediated anthropophilic host-seeking behavior of An. gambiae.

Characterization of Chemosensory Responses on the Labellum of the Malaria Vector Mosquito, Anopheles coluzzii

“…Notably, citral is a plant-based insect repellent used as a personal protection against host-seeking mosquitoes 21 . Among other odorant classes tested, carboxylic acids such as oxovaleric acid, pentanoic acid, hexanoic acid and heptanoic acid, which are known to be a part of human sweat and are important cues for host-seeking mosquitoes 24 , 25 , 28 , 29 , evoked robust neural responses and are likely to be sensed by the AgIrs 27 .…”

Hotspots and super-spreaders: Modelling fine-scale malaria parasite transmission using mosquito flight behaviour

“…In all focal areas, a mixture of wind-aided flight (downwind and downwind + random movements, upwind and upwind + random movements) were implicated in the majority of house-to-house transmissions: 96% in Focal area A, 58% in Focal area B, and 86% in Focal area C. Purely random movement (independent from wind) accounted for the majority of the connections in Focal area B only (around 42% of connections, Table 2 ). Importantly, active flight (upwind and upwind + random) is responsible for more than a third of connections in Focal area A and B and the majority of connections in Focal area C, supporting the epidemiological importance of upwind flight for mosquito dispersal and subsequent parasite transmission [ 46 , 47 ].…”

Identification of human skin bacteria attractive to the Asian Tiger mosquito

“…tuberculostearicum is that both strains produce specific malodorous thiol derivatives (Bawdon et al ., ) that were shown to affect A . gambiae responsiveness (Frei et al ., ). However, we did not detect these compounds, nor any specific other compound produced by these two strains.…”