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Host-specific cues cause differential attractiveness of Kenyan men to the African malaria vector Anopheles gambiae.

Mukabana WR, Takken W, Coe R, Knols BG - Malar. J. (2002)

Bottom Line: Controls (empty tents) were included and the effect of residual odours following tent occupation was also examined.Presence (P < 0.001) or absence (P = 0.949) of significant differences in the number of mosquitoes caught per trap when tents were simultaneously occupied by one person in each or left empty, respectively, demonstrated that residual odours following tent occupation did not affect behavioural responses of the mosquitoes.We provide evidence that in the vicinity of humans, when exposed to a blend of physical and olfactory signals from more than one host, An. gambiae can effectively and consistently express host-selection behaviour that results in non-random biting.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya. rmukabana@uonbi.ac.ke

ABSTRACT

Background: Many studies have suggested that variability in the attractiveness of humans to host-seeking mosquitoes is caused by differences in the make-up of body emanations, and olfactory signals in particular. Most investigations have either been laboratory-based, utilising odour obtained from sections of the body, or have been done in the field with sampling methods that do not discriminate between visual, physical and chemical cues of the host. Accordingly, evidence for differential attractiveness based on body emanations remains sparse in spite of the far-reaching epidemiological implications of this phenomenon.

Methods: A new three-port olfactometer that accommodates complete human beings as sources of host-seeking stimuli was used to study behavioural responses of Anopheles gambiae Giles sensu stricto (hereafter An. gambiae) under semi-field conditions in western Kenya. Differential attractiveness of nine male Kenyans was assessed by simultaneously exposing the mosquitoes to (a mixture of) total body emanations of 3 people occupying separate tents. Controls (empty tents) were included and the effect of residual odours following tent occupation was also examined.

Results: Trap catches increased significantly (P < 0.001) when a tent was occupied. Based on 'competition' experiments, the nine persons were classified into least, medium and most attractive groups. There was no significant interaction between person and trap (P = 0.302) or person and test period (P = 0.223). Presence (P < 0.001) or absence (P = 0.949) of significant differences in the number of mosquitoes caught per trap when tents were simultaneously occupied by one person in each or left empty, respectively, demonstrated that residual odours following tent occupation did not affect behavioural responses of the mosquitoes.

Conclusion: We provide evidence that in the vicinity of humans, when exposed to a blend of physical and olfactory signals from more than one host, An. gambiae can effectively and consistently express host-selection behaviour that results in non-random biting.

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Related in: MedlinePlus

Top (A), cross-sectional (B) and three-dimensional (C) views of the experimental setup. The fan (a) drew air (~130 L/min/tent) from the three tents (b) to the outside environment via PVC pipes (c), trap chambers (d) and central choice chamber (e). Each trap chamber contained a collecting cage (f) into which an exit trap opened (g). The fan pipe and release cup (h) were fitted to the top and bottom of the choice chamber, respectively. Diagrams are not shown to scale; all dimensions are in centimeters.
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Figure 1: Top (A), cross-sectional (B) and three-dimensional (C) views of the experimental setup. The fan (a) drew air (~130 L/min/tent) from the three tents (b) to the outside environment via PVC pipes (c), trap chambers (d) and central choice chamber (e). Each trap chamber contained a collecting cage (f) into which an exit trap opened (g). The fan pipe and release cup (h) were fitted to the top and bottom of the choice chamber, respectively. Diagrams are not shown to scale; all dimensions are in centimeters.

Mentions: Experiments were conducted using an olfactometer designed to accommodate humans as sources of host-seeking stimuli (Figure 1). The set-up consisted of three tents connected to a central collecting system by polyvinyl chloride (PVC) pipes. The collecting system consisted of a choice chamber and three trap chambers. The choice chamber opened into mesh-covered collecting cages (12 × 12 × 12 cm), placed inside the trap chambers, through 8-cm (mouth diameter) funnels made of netting mesh. The collecting system, pipes and tents were covered with opaque polythene sheets to exclude visual cues. Tent-ends proximal to the collecting system had sleeves in which the pipes were fitted. Pipe-ends opening into trap chambers plus the fan-pipe, at its point of connection on the top lid, were covered with panels of mosquito netting. A CDC light-trap fan was used to draw air (~130 L/min/tent) from all three tents into the central chamber. The system was housed inside a large screen house (11.4 × 7.1 m) lined with mosquito netting along its walls. The roof of the screen house was covered with glass and the sides with mesh (density 90%). A layer of reed mats was placed beneath the roof so as to lower temperatures. The fan pipe was extended through the screen house wall, and delivered odour-laden air from the olfactometer to the outside of the screen house.


Host-specific cues cause differential attractiveness of Kenyan men to the African malaria vector Anopheles gambiae.

Mukabana WR, Takken W, Coe R, Knols BG - Malar. J. (2002)

Top (A), cross-sectional (B) and three-dimensional (C) views of the experimental setup. The fan (a) drew air (~130 L/min/tent) from the three tents (b) to the outside environment via PVC pipes (c), trap chambers (d) and central choice chamber (e). Each trap chamber contained a collecting cage (f) into which an exit trap opened (g). The fan pipe and release cup (h) were fitted to the top and bottom of the choice chamber, respectively. Diagrams are not shown to scale; all dimensions are in centimeters.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC149388&req=5

Figure 1: Top (A), cross-sectional (B) and three-dimensional (C) views of the experimental setup. The fan (a) drew air (~130 L/min/tent) from the three tents (b) to the outside environment via PVC pipes (c), trap chambers (d) and central choice chamber (e). Each trap chamber contained a collecting cage (f) into which an exit trap opened (g). The fan pipe and release cup (h) were fitted to the top and bottom of the choice chamber, respectively. Diagrams are not shown to scale; all dimensions are in centimeters.
Mentions: Experiments were conducted using an olfactometer designed to accommodate humans as sources of host-seeking stimuli (Figure 1). The set-up consisted of three tents connected to a central collecting system by polyvinyl chloride (PVC) pipes. The collecting system consisted of a choice chamber and three trap chambers. The choice chamber opened into mesh-covered collecting cages (12 × 12 × 12 cm), placed inside the trap chambers, through 8-cm (mouth diameter) funnels made of netting mesh. The collecting system, pipes and tents were covered with opaque polythene sheets to exclude visual cues. Tent-ends proximal to the collecting system had sleeves in which the pipes were fitted. Pipe-ends opening into trap chambers plus the fan-pipe, at its point of connection on the top lid, were covered with panels of mosquito netting. A CDC light-trap fan was used to draw air (~130 L/min/tent) from all three tents into the central chamber. The system was housed inside a large screen house (11.4 × 7.1 m) lined with mosquito netting along its walls. The roof of the screen house was covered with glass and the sides with mesh (density 90%). A layer of reed mats was placed beneath the roof so as to lower temperatures. The fan pipe was extended through the screen house wall, and delivered odour-laden air from the olfactometer to the outside of the screen house.

Bottom Line: Controls (empty tents) were included and the effect of residual odours following tent occupation was also examined.Presence (P < 0.001) or absence (P = 0.949) of significant differences in the number of mosquitoes caught per trap when tents were simultaneously occupied by one person in each or left empty, respectively, demonstrated that residual odours following tent occupation did not affect behavioural responses of the mosquitoes.We provide evidence that in the vicinity of humans, when exposed to a blend of physical and olfactory signals from more than one host, An. gambiae can effectively and consistently express host-selection behaviour that results in non-random biting.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya. rmukabana@uonbi.ac.ke

ABSTRACT

Background: Many studies have suggested that variability in the attractiveness of humans to host-seeking mosquitoes is caused by differences in the make-up of body emanations, and olfactory signals in particular. Most investigations have either been laboratory-based, utilising odour obtained from sections of the body, or have been done in the field with sampling methods that do not discriminate between visual, physical and chemical cues of the host. Accordingly, evidence for differential attractiveness based on body emanations remains sparse in spite of the far-reaching epidemiological implications of this phenomenon.

Methods: A new three-port olfactometer that accommodates complete human beings as sources of host-seeking stimuli was used to study behavioural responses of Anopheles gambiae Giles sensu stricto (hereafter An. gambiae) under semi-field conditions in western Kenya. Differential attractiveness of nine male Kenyans was assessed by simultaneously exposing the mosquitoes to (a mixture of) total body emanations of 3 people occupying separate tents. Controls (empty tents) were included and the effect of residual odours following tent occupation was also examined.

Results: Trap catches increased significantly (P < 0.001) when a tent was occupied. Based on 'competition' experiments, the nine persons were classified into least, medium and most attractive groups. There was no significant interaction between person and trap (P = 0.302) or person and test period (P = 0.223). Presence (P < 0.001) or absence (P = 0.949) of significant differences in the number of mosquitoes caught per trap when tents were simultaneously occupied by one person in each or left empty, respectively, demonstrated that residual odours following tent occupation did not affect behavioural responses of the mosquitoes.

Conclusion: We provide evidence that in the vicinity of humans, when exposed to a blend of physical and olfactory signals from more than one host, An. gambiae can effectively and consistently express host-selection behaviour that results in non-random biting.

Show MeSH
Related in: MedlinePlus