Flavivirus surveillance in mosquitoes from northern Colorado, with the detection and description of two insect-specific flaviviruses.

摘要

Vector-borne diseases remain a major public health concern worldwide. The studies described here underline the importance of combining field surveillance activities with laboratory experiments to provide a comprehensive understanding of the dynamics of vector-borne disease systems.;Entomological measures of West Nile virus (WNV) risk were found to be strongly associated with human WNV disease cases in northeastern Colorado. Specifically, Culex tarsalis abundance and the Vector Index for WNV-infected Cx. tarsalis females (weekly mean per trap night x weekly proportion of WNV-infected females) were associated with weekly numbers of WNV human disease cases with lag times of 4--7 weeks and 1--2 weeks, respectively. This provides information that can be utilized for decision-making processes concerning when to initiate mosquito control activities and how to best utilize limited resources.;These studies also describe the first detection of insect-specific flaviviruses in mosquitoes collected in Colorado. Culex flavivirus (CXFV), first described in Japan in 2007, and a new insect-specific flavivirus, designated Calbertado virus, were detected in Culex spp. mosquitoes. Experiments were conducted to explore the transmission dynamics of CXFV in a naturally infected Culex pipiens laboratory colony and also the potential effects of CXFV infection on vector competence for WNV. Results indicated that vertical transmission is the primary mechanism for viral persistence in the colony, with venereal transmission perhaps playing a supplemental role. Vector competence experiments suggested possible suppression of WNV replication by persistent CXFV infection. These findings are important as insect-specific flavivirus transmission dynamics have not been described yet and studies investigating putative interactions between insect-specific flaviviruses with arboviruses, like WNV, are lacking.;This work provides a better understanding of local vector-borne disease systems, providing a basis for additional studies to further characterize the dynamics of co-circulating flaviviruses in vector mosquitoes.