Unexpected spatiotemporal abundance of infected Culex restuans suggest a greater role as a West Nile virus vector for this native species Brian J. Johnson ⇑ , Mark G. Robson, Dina M. Fonseca Graduate Program in Ecology and Evolution, Rutgers University, 14 College Farm Rd, New Brunswick, NJ 08901, USA Center for Vector Biology, Department of Entomology, Rutgers University, 180 Jones Ave, New Brunswick, NJ 08901, USA article info Article history: Received 23 September 2014 Received in revised form 6 January 2015 Accepted 7 January 2015 Available online 16 January 2015 Keywords: Enzootic Epidemic Wetlands Urbanization Anthropogenic disturbance Native invader abstract Difficulties in correctly differentiating Culex restuans mosquitoes from Culex pipiens have left the spatio- temporal mechanisms underlying the epidemiology of West Nile virus (WNV) in the northeastern United States largely unresolved. We performed weekly surveys across a natural to urban gradient of sites in central New Jersey (USA) and used a rapid and cheap DNA extraction and a species-specific PCR assay to create single species pools for WNV testing. To assess seasonal trends we combined these results with WNV surveillance records generated from grouped Cx. restuans/Cx. pipiens pools tested in 2011and 2012. Cx. restuans was found to be highly abundant within all sites and reached especially high abundance in urban wetland habitats greatly disturbed by human action. In contrast, the seasonal presence of Cx. pipiens was greatest in residential and urban habitats and its presence in natural areas was minimal throughout the season. WNV infection rates in both species were similar but Cx. restuans was consistently found infected first and more frequently, even as early as May, whereas WNV was first detected in Cx. pipiens in late July. WNV activity peaked during the month of August when WNV was commonly isolated from both species. The peak in WNV activity in August observed for both species was consistent with data from 2011 to 2012 when Cx. restuans and Cx. pipiens were grouped, although analyzing single species pools increased overall predicted infection levels. Our results support the preeminence of Cx. restuans as an enzootic vec- tor of WNV and strongly suggest this species has become a ‘‘native invasive’’ exploiting human modified habitats and reaching very high abundance there. Importantly, high infection rates in disturbed wetland sites with high populations of Cx. restuans suggest this species may enable the introduction of WNV to urbanized environments where both Culex contribute to transmission potentiating disease risk. Ó 2015 Published by Elsevier B.V. 1. Introduction Differentiating adult females of Culex restuans, a mosquito endemic to North America, from Culex pipiens, an ecologically similar but exotic species introduced from Europe, using mor- phological characteristics is largely unreliable (Ebel et al., 2005; Farajollahi et al., 2011; Harrington and Poulson, 2008). Consequently, the two species are frequently misidentified and are commonly lumped together in West Nile virus (WNV) test- ing (Ebel et al., 2005; Harrington and Poulson, 2008). This prac- tice has left the determination of the seasonal and spatial importance of each species in the transmission of WNV in the northeastern United States largely unresolved. Although many public health and mosquito control professionals recognize these limitations, Cx. pipiens is still touted as the primary vector of WNV in the Northeast since it is considered the predominant Culex in urban areas, thought to be commonly infected with the virus, and human cases of WNV rise during its peak abundance period in mid-late summer (Kilpatrick et al., 2005; Kramer et al., 2008). However, surveys of larvae, which have distinct morphologies in the two species, have found high abun-dance, even predominance of Cx. restuans in highly urbanized settings (Ebel et al., 2005). The lack of accurate identification of the adults, therefore, may have led to the perpetuation of potentially inaccurate understandings of the ecological and epi-demiological importance of each species in the transmission of WNV. Cx. restuans is a cold-tolerant species and is considered the undisputed early season vector of WNV in the northeastern US (Andreadis et al., 2001; Reiskind and Wilson, 2008; Reiter, 2007). However, the abundance of Cx. restuans is commonly thought to http://dx.doi.org/10.1016/j.meegid.2015.01.007 1567-1348/Ó 2015 Published by Elsevier B.V. ⇑ Corresponding author at: Center for Vector Biology, 180 Jones Ave., New Brunswick, NJ 08901, USA. Tel.: +1 309 569 1262. E-mail address: brijo85@rci.rutgers.edu (B.J. Johnson). Infection, Genetics and Evolution 31 (2015) 40–47 Contents lists available at ScienceDirect Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid