Culex pipiens(Diptera: Culicidae): A Bridge Vector of West Nile Virus to Humans

Abstract

Host-feeding patterns of Culex pipiens L. collected in southwest suburban Chicago in 2005 were studied using polymerase chain reaction (PCR) and DNA sequencing techniques. Culex spp. mosquitoes, most identified to Cx. pipiens and the remainder to Cx. restuans by PCR, had fed on 18 avian species, most commonly American robin (Turdus migratorious), house sparrow (Passer domesticus), and mourning dove (Zenaida macroura). Additional blood meals were derived from four mammal species, primarily humans and raccoons (Procyon lotor). During a West Nile virus (WNV) epidemic in 2005, West Nile virus (WNV) RNA was detected in heads and thoraces of five Cx. pipiens (n = 335, 1.5%) using quantitative PCR. The hosts of these virus-infected, blood-fed mosquitoes included two American robins, one house sparrow, and one human. This is the first report of a WNV-infected Cx. pipiens mosquito collected during an epidemic of WNV that was found to have bitten a human. These results fulfill a criterion for incrimination of Cx. pipiens as a bridge vector.

Culex Flavivirus and West Nile Virus Mosquito Coinfection and Positive Ecological Association in Chicago, United States

“…Mosquitoes were collected from our study area in the southwestern Chicago suburbs (*150 km 2 in Cook County; 87844 0 W, 41842 0 N), from 4 urban green space sites (cemeteries and parks) and 11 residential sites (characterized by dense housing and impermeable surfaces) (Bertolotti et al 2008, Hamer et al 2008a. A total of 1076 mosquito pools were available from 2006, a year of particularly high WNV transmission (Ruiz et al 2010).…”

“…Mosquitoes were captured using CO 2 -baited Centers for Disease Control and Prevention miniature light traps, Centers for Disease Control and Prevention gravid traps baited with rabbit pellet infusion, and batterypowered backpack aspirators. Mosquitoes were identified (Andreadis et al 2005); pooled into groups of 31 or fewer; grouped by species, sex, collection site, and date; and processed for extraction of RNA, which was then frozen at À808C for archiving after WNV testing by real-time reverse-transcription polymerase chain reaction (RT-PCR) (Hamer et al 2008a).…”

“…In particular, WNV transmission in this area is driven by Cx. pipiens, the dominant WNV vector in the Eastern and Midwestern United States and a bridge vector between avian and human hosts (Hamer et al 2008a).…”

Phenotypic Variation among Culex pipiens Complex (Diptera: Culicidae) Populations from the Sacramento Valley, California: Horizontal and Vertical Transmission of West Nile Virus, Diapause Potential, Autogeny, and Host Selection

“…quinquefasciatus females are primarily ornithophilic 14 ; however, they also serve as important bridge vectors of WNV to humans. [26][27][28][29] In contrast, f. molestus is considered to be mammalophilic, with humans frequently the primary host. 6 It was hypothesized that hybridization between these forms may make Cx.…”

Spatial and Temporal Variation in Vector Competence of Culex pipiens and Cx. restuans Mosquitoes for West Nile Virus

“…[10][11][12] Several studies have identified key aspects of WNV amplification, including the competence or infectiousness of different avian hosts, 11,13,14 some habitatspecific associations of WNV, [15][16][17][18] and the vector competence and feeding patterns of Culex mosquitoes, the dominant vectors for WNV between birds, and also to humans in some areas. [19][20][21][22][23][24] The vector competence of colonized and field populations of mosquitoes for WNV has received substantial attention. It has been found to vary among vector species and genera, 10,[25][26][27][28][29] days since feeding, [30][31][32] strain of WNV, [30][31][32] and temperature 31,33 during the extrinsic incubation period.…”