Terrestrial vegetation and aquatic chemistry influence larval mosquito abundance in catch basins, Chicago, USA

Abstract

BackgroundAn important determinant of mosquito-borne pathogen transmission is the spatial distribution of vectors. The primary vectors of West Nile virus (WNV) in Illinois are Culex pipiens Linnaeus (Diptera: Culicidae) and Culex restuans Theobald. In urban environments, these mosquitoes commonly oviposit in roadside storm water catch basins. However, use of this habitat is inconsistent, with abundance of larvae varying significantly across catch basins at a fine spatial scale.MethodsWe tested the hypothesis that attributes of the biotic and abiotic environment contribute to spatial and temporal variation in production of mosquito vectors, characterizing the relationship between terrestrial vegetation and aquatic chemistry and Culex abundance in Chicago, Illinois. Larvae were sampled from 60 catch basins from June 14 to October 3, 2009. Density of shrubs and 14 tree genera surrounding the basins were quantified, as well as aquatic chemistry content of each basin.ResultsWe demonstrate that the spatial pattern of Culex abundance in catch basins is strongly influenced by environmental characteristics, resulting in significant variation across the urban landscape. Using regression and machine learning techniques, we described landscape features and microhabitat characteristics of four Chicago neighborhoods and examined the implications of these measures for larval abundance in adjacent catch basins. The important positive predictors of high larval abundance were aquatic ammonia, nitrates, and area of shrubs of height <1 m surrounding the catch basins, whereas pH and area of flowering shrub were negatively correlated with larval abundance. Tree density, particularly of arborvitae, maple, and pear, also positively influenced the distribution of Culex during the fruit-bearing periods and early senescent periods in August and September.ConclusionsThis study identifies environmental predictors of mosquito production in urban environments. Because an abundance of adult Culex is integral to efficient WNV transmission and mosquitoes are found in especially high densities near larval habitats, identifying aquatic sites for Culex and landscape features that promote larval production are important in predicting the spatial pattern of cases of human and veterinary illness. Thus, these data enable accurate assessment of regions at risk for exposure to WNV and aid in the prevention of vector-borne disease transmission.

Mosquito Vector Diversity across Habitats in Central Thailand Endemic for Dengue and Other Arthropod-Borne Diseases

“…The mechanisms underlying this pattern are not well understood, but some have suggested the positive effect of habitat diversity on mosquito species diversity [48], [49], or that increased stress and pollution in urban habitats favor certain invasive genera such as Culex , which is more adaptable to a variety of habitats and may competitively exclude other species [50], [51], [52]. We suspect that the urban environments in our study may have had fewer kinds of aquatic habitats that different female mosquitoes could exploit, thus favoring human-adapted mosquitoes such as Aedes aegypti and Culex quinquefasciatus .…”

Reduced productivity ofCulex pipiensandCx. restuans(Diptera: Culicidae) mosquitoes in parking area catch basins in the northeast Chicago metropolitan area

“…This suggests that fallen detritus from these trees is captured in basin sumps and that this captured organic detritus is associated with increased pupal abundance. The association with catch basin mosquito abundance and trees has been made elsewhere (Gardner et al 2013). Certainly the close Figure 2.…”

“…This suggests that fallen detritus from these trees is captured in basin sumps and that this captured organic detritus is associated with increased pupal abundance. The association with catch basin mosquito abundance and trees has been made elsewhere (Gardner et al ). Certainly the close proximity of multiple deciduous trees to basins may not always result in high productivity, however, identifying basins located close to deciduous trees could be useful to identify the risk for increased productivity.…”

Invasive species reduces parasite prevalence and neutralizes negative environmental effects on parasitism in a native mosquito

“…In a field survey, infection levels in Ae . triseriatus were not correlated with pH, conductivity or water temperature (Van Rhein et al, ), but field surveys have found wide natural variation in gregarine parasite infection levels (Comiskey, Lowrie, & Wesson, ; Mlynarek, Bert, Haydeé Peralta‐Vázquez, James, & Forbes, ; Van Rhein et al, ), which may partly result from differences in phenolic compounds and concentrations arising from different types and quantities of detritus that accumulate in these aquatic habitats (Earl & Semlitsch, ; Gardner et al, ; Kling, Juliano, & Yee, ; Stoler et al, ).…”