Entomology
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Item Spatiotemporal organization of cryptic North American Culex species along an urbanization gradient(Wiley, 2023-10-03) Arsenault-Benoit, Arielle; Fritz, Megan L.Landscape heterogeneity creates diverse habitat and resources for mosquito vectors of disease. A consequence may be varied distribution and abundance of vector species over space and time dependent on niche requirements. We tested the hypothesis that landscape heterogeneity driven by urbanization influences the distribution and relative abundance of Culex pipiens, Cx. restuans and Cx. quinquefasciatus, three vectors of West Nile virus (WNv) in the eastern North American landscape. We collected 9803 cryptic Culex from urban, suburban and rural sites in metropolitan Washington, District of Columbia, during the months of June–October, 2019–2021. In 2021, we also collected mosquitoes in April and May to measure early season abundance and distribution. Molecular techniques were used to identify a subset of collected Culex to species (n = 2461). Ecological correlates of the spatiotemporal distribution of these cryptic Culex were examined using constrained and unconstrained ordination. Seasonality was not associated with Culex community composition in June–October over 3 years, but introducing April and May data revealed seasonal shifts in community composition in the final year of our study. Culex pipiens were dominant across site types, while Cx. quinquefasciatus were associated with urban environments, and Cx. restuans were associated with rural and suburban sites. All three species rarely coexisted. Our work demonstrates that human-mediated land-use changes influence the distribution and relative abundance of Culex vectors of WNv, even on fine geospatial scales. Site classification, per cent impervious surface, distance to city centre and longitude predicted Culex community composition. We documented active Culex months before vector surveillance typically commences in this region, with Culex restuans being most abundant during April and May. Active suppression of Cx. restuans in April and May could reduce early enzootic transmission, delay the seasonal spread of WNv and thereby reduce overall WNv burden. By June, the highest risk of epizootic spillover of WNv to human hosts may be in suburban areas with high human population density and mixed Culex assemblages that can transmit WNv between birds and humans. Focusing management efforts there may further reduce human disease burden.Item Human biting mosquitoes and implications for West Nile virus transmission(Springer Nature, 2023-01-02) Uelmen, Johnny A. Jr.; Lamcyzk, Bennett; Irwin, Patrick; Bartlett, Dan; Stone, Chris; Mackay, Andrew; Arsenault-Benoit, Arielle; Ryan, Sadie J.; Mutebi, John-Paul; Hamer, Gabriel L.; Fritz, Megan; Smith, Rebecca L.West Nile virus (WNV), primarily vectored by mosquitoes of the genus Culex, is the most important mosquito-borne pathogen in North America, having infected thousands of humans and countless wildlife since its arrival in the USA in 1999. In locations with dedicated mosquito control programs, surveillance methods often rely on frequent testing of mosquitoes collected in a network of gravid traps (GTs) and CO2-baited light traps (LTs). Traps specifically targeting oviposition-seeking (e.g. GTs) and host-seeking (e.g. LTs) mosquitoes are vulnerable to trap bias, and captured specimens are often damaged, making morphological identification difficult. This study leverages an alternative mosquito collection method, the human landing catch (HLC), as a means to compare sampling of potential WNV vectors to traditional trapping methods. Human collectors exposed one limb for 15 min at crepuscular periods (5:00–8:30 am and 6:00–9:30 pm daily, the time when Culex species are most actively host-seeking) at each of 55 study sites in suburban Chicago, Illinois, for two summers (2018 and 2019). A total of 223 human-seeking mosquitoes were caught by HLC, of which 46 (20.6%) were mosquitoes of genus Culex. Of these 46 collected Culex specimens, 34 (73.9%) were Cx. salinarius, a potential WNV vector species not thought to be highly abundant in upper Midwest USA. Per trapping effort, GTs and LTs collected > 7.5-fold the number of individual Culex specimens than HLC efforts. The less commonly used HLC method provides important insight into the complement of human-biting mosquitoes in a region with consistent WNV epidemics. This study underscores the value of the HLC collection method as a complementary tool for surveillance to aid in WNV vector species characterization. However, given the added risk to the collector, novel mitigation methods or alternative approaches must be explored to incorporate HLC collections safely and strategically into control programs.