RESUMEN
The African malaria mosquito Anopheles gambiae exhibits a strong innate drive to seek out humans in its sensory environment, classically entering homes to land on human skin in the hours flanking midnight. To gain insight into the role that olfactory cues emanating from the human body play in generating this epidemiologically important behavior, we developed a large-scale multi-choice preference assay in Zambia with infrared motion vision under semi-field conditions. We determined that An. gambiae prefers to land on arrayed visual targets warmed to human skin temperature during the nighttime when they are baited with carbon dioxide (CO2) emissions reflective of a large human over background air, body odor from one human over CO2, and the scent of one sleeping human over another. Applying integrative whole body volatilomics to multiple humans tested simultaneously in competition in a six-choice assay, we reveal high attractiveness is associated with whole body odor profiles from humans with increased relative abundances of the volatile carboxylic acids butyric acid, isobutryic acid, and isovaleric acid, and the skin microbe-generated methyl ketone acetoin. Conversely, those least preferred had whole body odor that was depleted of carboxylic acids among other compounds and enriched with the monoterpenoid eucalyptol. Across expansive spatial scales, heated targets without CO2 or whole body odor were minimally or not attractive at all to An. gambiae. These results indicate that human scent acts critically to guide thermotaxis and host selection by this prolific malaria vector as it navigates towards humans, yielding intrinsic heterogeneity in human biting risk.
Asunto(s)
Anopheles , Malaria , Taxia , Animales , Humanos , Odorantes , Olor Corporal , Dióxido de Carbono , Mosquitos Vectores , Feromonas Humanas , Ácidos CarboxílicosRESUMEN
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.