Associate Professor Colorado State University Fort Collins, Colorado
Many questions remain about the risk factors for establishment of Rift Valley fever virus (RVFV) in new geographic areas. If this virus invades North America, it would have a devastating economic and health impacts to the livestock industry in addition to causing a public health emergency. Due to the local abundance and opportunistic host selection of Cx. tarsalis mosquitoes, we hypothesized that this species could be a locally important bridge vector of RVFV near feedlots in Colorado. We investigated the mosquito community composition at livestock feedlots and surrounding natural areas to determine differences in mosquito relative abundance and blood feeding patterns attributed to cattle feeding operations. DNA extracted from mosquito blood meals were sequenced to determine host identity, and the infection, dissemination, and transmission rates of epidemic RVFV KEN128B-15 was assessed for experimentally challenged, wild-caught Cx. tarsalis, Culiseta inornata, Aedes vexans, Ae. melanimon, and Ae. increpitus. Multivariate regression analyses revealed differences between mosquito community assemblages at feedlots and non-feedlot sites, with this effect driven by differential abundances of Ae. vexans. Mosquito diversity was lower on feedlots than surrounding areas. Diverse vertebrate blood meals were detected in Cx. tarsalis at non-feedlot sites, with a shift towards feeding on cattle at feedlots. All five Colorado mosquito species evaluated were capable of transmitting RVFV. These data support a potential for Cx. tarsalis to serve as a bridge vector of RVFV between livestock and humans in Colorado, with potential contribution to transmission by a diversity of additional species.
