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United States Department of Agriculture

Agricultural Research Service

Research Project: Chemical Biology of Insect and Plant Signaling Systems

Location: Chemistry Research Unit

Title: Behavioural response of the malaria vector Anopheles gambiae to host plant volatiles and synthetic blends

Authors
item Nyasembe, Vincent -
item TEAL, PETER
item Mukabana, Volfgang -
item Tumlinson, James -
item Torto, Baldwyn -

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 8, 2012
Publication Date: October 15, 2012
Citation: Nyasembe, V.0., Teal, P.E., Mukabana, V.R., Tumlinson, J.H., Torto, B. 2012. Behavioural response of the malaria vector Anopheles gambiae to host plant volatiles and synthetic blends. Parasites & Vectors. 5:234.

Interpretive Summary: Although it is often thought that mosquitoes that vector malaria feed only on blood they also feed on plant nectar to obtain sugars required for energy. Indeed, without feeding on nectar the mosquitoes will die. Scientists at the International Centre of Insect Physiology and Ecology, Nairobi, Kenya, School of Biological Sciences, University of Nairobi, Kenya, the Chemistry Research Unit of the Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS Gainesville, FL., and the Center for Chemical Ecology, Department of Entomology, Pennsylvania State University, University Park, PA 16802, USA. Explored the odors emitted from plants that attract these vectors of malaria. They discovered that the mosquitoes were attracted to a series of six chemicals emitted by plants. In field tests the scientists were able to formulate a blend of these chemicals that was far more attractive than any of the blends naturally produced by the plants studied. The research provides a practical and inexpensive new attractant for female mosquitoes that will be of great significance in monitoring the prevalence of this malaria vector in regions where it occurs.

Technical Abstract: Sugar feeding is critical for survival of malaria vectors and, although discriminative plant feeding previously has been shown to occur in Anopheles gambiae s.s., little is known about the cues mediating attraction to these plants. In this study, we investigated the role of olfaction in An. gambiae discriminative feeding behaviour. Dual choice olfactometer assays were used to study odour discrimination by An. gambiae to three suspected host plants: Parthenium hysterophorus (Asteraceae), Bidens pilosa (Asteraceae) and Ricinus communis (Euphorbiaceae). Sugar content of the three plant species was determined by analysis of their trimethylsilyl derivatives by coupled gas chromatography-mass spectrometry (GC-MS) and confirmed with authentic standards. Volatiles from intact plants of the three species were collected on Super Q and analyzed by coupled GC-electroantennographic detection (GC-EAD) and GC-MS to identify electrophysiologically-active components whose identities were also confirmed with authentic standards. Behaviourally-active compounds and blends were formulated using dose-response olfactory bioassays. Overall, although the amounts of sugar contents were similar in the two Asteraceae plants, P. hysterophorus and B. pilosa, but richer in R. communis. Odours released by P. hysterophorus were the most attractive, with those from B. pilosa being the least attractive to females in the olfactometer assays. Six EAG-active components identified, were consistently detected by the antennae of adult females. The amounts of common antennally-active components released varied with the host plant, with the highest amounts released by P. hysterophorus. In dose-response assays, single compounds and blends of these components were attractive to females but to varying levels, with one of the blends recording a significantly attractive response from females when compared to volatiles released by either the most preferred plant, P. hysterophorus (t = 2.868, df = 4, P < 0.05). or as synthetic blend mimicking that released by P. hysterophorus. Our results demonstrate that (a) a specific group of plant odours attract female An. gambiae (b) females use both qualitative and quantitative differences in volatile composition to associate and discriminate between different host plants, and (c) altering concentrations of individual EAG-active components in a blend provides a practical direction for developing effective plant-based lures for malaria vector management.

Last Modified: 8/27/2014
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