The nose knows: Using the olfactory system to dissect mosquito host-seeking behavior

Mosquitoes that feed on humans transmit deadly diseases that affect hundreds of millions of people every year.  Host-seeking is a robust model for understanding complex behavior elicited by complex stimuli:  females use a combination of carbon dioxide and skin cues to find and select human hosts from a distance.  With a few exceptions, most of the odor compounds that mosquitoes use to find us have not been identified, including those that attract mosquitoes in the absence of carbon dioxide and those that make some people more attractive than others.  My work has targeted specific components of the olfactory system to determine how they contribute to different aspects of host-seeking behavior.  For example, electrophysiology assays identified a specific olfactory receptor neuron (ORN) class that responds to both CO₂ and to skin odor.  This response is conserved in both Aedes aegypti and Anopheles gambiae, even though these two species are not closely related.  I specifically suppress the activity of this ORN for hours by treatment with a reactive compound that is structurally related to known ligands.  After treatment, mosquitoes show characteristic deficits in navigation toward human skin odor.  Ongoing work is extending these methods to other aspects of host-seeking behavior.