Abstract. La Crosse virus (LACV), a leading cause of arboviral pediatric encephalitis in the United States, is emerging in Appalachia. Here, we report field and laboratory evidence that suggest LACV may be using Culex mosquitoes as additional vectors in this region. This bunyavirus was detected by reverse-transcriptase polymerase chain reaction in two pools of Culex mosquitoes in southwestern Virginia and in six pools in West Virginia. To assess vector competence, we offered LACV blood meals to field-collected Culex restuans Theobald, Cx. pipiens L., and Aedes triseriatus (Say). Both Culex species were susceptible to infection. LACV-positive salivary expectorate, indicative of the ability to transmit, was detected in a small proportion of Cx. restuans (9%) and Cx. pipiens (4%) compared with Ae. triseriatus (40%). In a companion study of Cx. restuans only, we found that adults derived from nutritionally stressed larvae were significantly more likely to disseminate and transmit LACV. Our results indicate a potential role of Culex spp. in LACV dynamics that should be explored further in endemic areas.

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Variability in the chemical composition of human scent has the potential to modulate mosquito attraction to certain humans. We have engineered a large-scale, semi-field system in Zambia for quantifying mosquito olfactory preferences towards whole body odor sourced from different humans under naturalistic conditions. In a flight cage arena with infrared tracking, we document that the African malaria mosquitoAnopheles gambiaehierarchically prefers to land on heated targets mimicking human skin temperature when they are baited with carbon dioxide (CO2) over background air, human body odor over CO2, and the scent of one individual over another. In a six-choice assay configuration, we further identify humans at both ends of the attractiveness spectrum whose scent is differentially attractive toAn. gambiaerelative to other individuals. We demonstrate integrative use of this multi-choice olfactory assay with whole body volatilomics, establishing a powerful method for discovery of human odorants modulating heterogeneity in biting risk at enhanced throughput.