A Behavioral Assay to Quantify Odor-Guided Thermotaxis with Anopheles gambiae under Semi-Field Conditions

Quantifying Mosquito Host Preference

The most dangerous mosquito species for human health are those that blood feed preferentially and frequently on humans (anthropophilic mosquitoes). These include prolific disease vectors such as the African malaria mosquito Anopheles gambiae and yellow fever mosquito Aedes aegypti The chemosensory basis for anthropophilic behavior exhibited by these disease vectors, as well as the factors that drive interindividual differences in human attractiveness to mosquitoes, remain largely uncharacterized. Here, we concisely review established methods to quantify mosquito interspecific and intraspecific host preference in the laboratory, as well as semi-field and field environments. Experimental variables for investigator consideration during assays of mosquito host preference across these settings are highlighted.

Quantification of Anopheles gambiae Olfactory Preferences under Semi-Field Conditions

Anopheles gambiae is a highly anthropophilic (human-preferring) malaria vector that prefers to blood feed frequently and selectively on humans. This mosquito species exhibits a strong innate olfactory preference to seek out human scent over other animals, and certain humans over others-key behavioral traits with the potential to drive heterogeneity in biting risk and malaria transmission. Here, we describe the application of a large-scale, semi-field system in Zambia for the quantification of An. gambiae olfactory preferences toward whole body odor sourced from individual humans. We detail steps for modifying one-person canvas tents to duct odor from sleeping humans into a central, semi-field flight cage arena that is securely screened. Using this system, we describe a protocol to perform two-choice olfactory preference assays with two human volunteers using laboratory-reared An. gambiae and odor-guided thermotaxis assays that leverage infrared video tracking to quantify mosquito landings on heated targets baited with each body odor sample. This multichoice olfactory preference assay has the potential to be applied with expanded cohorts of humans to define the chemosensory basis of An. gambiae host preference and interindividual differences in human attractiveness to mosquitoes and to be used to quantify the effects of protective measures such as personal and spatial repellents on mosquito landing behavior.