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Title: Host-seeking behaviour in the malaria vector Anopheles gambiae
Author: Hawkes, Frances Madeline
Awarding Body: University of Greenwich
Current Institution: University of Greenwich
Date of Award: 2013
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In sub-Saharan Africa, 90% of malaria cases are the result of transmission by the Anopheles gambiae species complex, causing 600,000 deaths annually. Increasingly, An. gambiae demonstrate behavioural and physiological resistance to control interventions and this, coupled with inadequate sampling methods, necessitates urgent development of new, efficient monitoring and control tools for malarial mosquitoes. The aim of this project was to examine the host-seeking behaviour of female An. gambiae to identify behavioural attributes that could be exploited in the design of novel trapping systems. To facilitate this, a wind tunnel arena with three-dimensional video-tracking was developed to quantify host-seeking flight of An. gambiae when presented with host-associated stimuli. In a constant flow of carbon dioxide and human-derived volatiles, mosquitoes were most active early in the night, suggesting a periodic responsiveness to olfactory stimuli, priming them to respond to potential hosts early in the night. Later spontaneous activity may increase the likelihood of encountering host odour plumes. Mosquitoes exhibited smooth and tortuous flight in up, down and crosswind directions in flows of clean and host odour-laden air, demonstrating a flexible suite of host-seeking behaviours. It is proposed that ‘dipping’ flight, consisting of high frequency vertical oscillations, may represent an alternative strategy to optomotor-guided anemotaxis in very low-light levels. When presented with black and clear targets in a flow of host odour-laden air, mosquitoes closely approached both targets more frequently than in a flow of clean air. Black targets were approached more frequently and collision avoidance was characterised by a rapid change to steep vertical flight. That mosquitoes avoided colliding with clear targets suggests involvement of an un-described sensory mechanism for detecting surfaces. Based on these findings, a prototype sticky trap incorporating a visual cue was tested in a malaria endemic region of Burkina Faso. The visually conspicuous trap caught more An. gambiae than a control trap, although both were equally efficient; additional design features could further optimise the visual trap. Overall, project results indicate that female An. gambiae exhibit a variety of integrated stimuli-response mechanisms that control navigation through the environment and towards potential hosts. Furthermore, they validate the approach of using quantified behaviours to improve the efficacy of monitoring tools.
Supervisor: Gibson, Gabriella ; Torr, Stephen Sponsor: University of Greenwich Research and Enterprise Fund
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QL Zoology