The survival of adult female Aedes mosquitoes is a critical component of their ability to transmit pathogens such as dengue viruses. One of the principal determinants of Aedes survival is temperature, which has been associated with seasonal changes in Aedes populations and limits their geographical distribution. The effects of temperature and other sources of mortality have been studied in the field, often via mark-release-recapture experiments, and under controlled conditions in the laboratory. Survival results differ and reconciling predictions between the two settings has been hindered by variable measurements from different experimental protocols, lack of precision in measuring survival of free-ranging mosquitoes, and uncertainty about the role of age-dependent mortality in the field.
Summary: Urban transmission of arthropod‐vectored disease has increased in recent decades. Understanding and managing transmission potential in urban landscapes requires integration of sociological and ecological processes that regulate vector population dynamics, feeding behaviour and vector–pathogen interactions in these unique ecosystems. Vectorial capacity is a key metric for generating predictive understanding about transmission potential in systems with obligate vector transmission. This review evaluates how urban conditions, specifically habitat suitability and local temperature regimes, and the heterogeneity of urban landscapes can influence the biologically relevant parameters that define vectorial capacity: vector density, survivorship, biting rate, extrinsic incubation period and vector competence. Incidence of vector‐borne disease in urban host populations is rarely, if ever, evenly distributed across an urban area. The persistence and quality of vector habitat can vary significantly across socio‐economic boundaries to influence vector species composition and abundance, often generating socio‐economically distinct gradients of transmission potential across neighbourhoods. Urban regions often experience unique temperature regimes, broadly termed urban heat islands (UHI). Arthropod vectors are ectothermic organisms, and their growth, survival and behaviour are highly sensitive to environmental temperatures. Vector response toUHIconditions is dependent on regional temperature profiles relative to the vector's thermal performance range. In temperate climates,UHIcan facilitate increased vector development rates while having countervailing influence on survival and feeding behaviour. Understanding how urban heat island (UHI) conditions alter thermal and moisture constraints across the vector life cycle to influence transmission processes is an important direction for both empirical and modelling research. There remain persistent gaps in understanding of vital rates and drivers in mosquito‐vectored disease systems, and vast holes in understanding for other arthropod‐vectored diseases. Empirical studies are needed to better understand the physiological constraints and socio‐ecological processes that generate heterogeneity in critical transmission parameters, including vector survival and fitness. Likewise, laboratory experiments and transmission models must evaluate vector response to realistic field conditions, such as variability in sociological and environmental conditions.
Mosquito-vectored pathogens are responsible for devastating human diseases and are (re)emerging in many urban environments. Effective mosquito control in urban landscapes relies on improved understanding of the complex interactions between the ecological and social factors that define where mosquito populations can grow. We compared the density of mosquito habitat and pupae production across economically varying neighborhoods in two temperate U.S. cities (Baltimore, MD and Washington, DC). Seven species of mosquito larvae were recorded. The invasive Aedes albopictus was the only species found in all neighborhoods. Culex pipiens, a primary vector of West Nile virus (WNV), was most abundant in Baltimore, which also had more tire habitats. Both Culex and Aedes pupae were more likely to be sampled in neighborhoods categorized as being below median income level in each city and Aedes pupae density was also greater in container habitats found in these lower income neighborhoods. We infer that lower income residents may experience greater exposure to potential disease vectors and Baltimore residents specifically, were at greater risk of exposure to the predominant WNV vector.However, we also found that resident-reported mosquito nuisance was not correlated with our measured risk index, indicating a potentially important mismatch between motivation needed to engage participation in control efforts and the relative importance of control among neighborhoods.
Arthropod-borne viruses (arboviruses) cause many diseases worldwide and their transmission is likely to change with land use and climate changes. La Crosse virus (LACV) is historically transmitted by the native mosquito Aedes triseriatus (Say) in the upper Midwestern US, but the invasive congeners Aedes albopictus (Skuse) and A. japonicus (Theobald), which co-occur with A. triseriatus in water-holding containers, may be important accessory vectors in the Appalachian region where La Crosse encephalitis is an emerging disease. This review focuses on evidence for how climate, land use, and biological invasions may have direct abiotic and indirect community-level impacts on immature developmental stages (eggs and larvae) of Aedes mosquitoes. Because vector-borne diseases usually vary in space and time and are related to the ecology of the vector species, we propose that the ecology of its mosquito vectors, particularly at their immature stages, has played an important role in the emergence of La Crosse encephalitis in the Appalachian region and represents a model for investigating the effects of environmental changes on other vector-borne diseases. We summarize the health effects of LACV and associated socioeconomic costs that make it the most important native mosquito-borne disease in the US. We review of the transmission of LACV, and present evidence for the impacts of climate, land use, and biological invasions on Aedes mosquito communities. Finally, we discuss important questions about the ecology of LACV mosquito vectors that may improve our understanding of the impacts of environmental changes on LACV and other arboviruses.
Social, ecological, and climatic factors interact creating a heterogeneous matrix that determines the spatiotemporal distribution of mosquitoes and human risks of exposure to the diseases they transmit. We explore linkages between the social and institutional processes behind residential abandonment, urban ecology, and the interactions of socio-ecological processes with abiotic drivers of mosquito production. Specifically, we test the relative roles of infrastructure degradation and vegetation for explaining the presence of Aedes albopictus Skuse 1894 to better predict spatial heterogeneity in mosquito exposure risk within urban environments. We further examine how precipitation interacts with these socially underpinned biophysical variables. We use a hierarchical statistical modeling approach to assess how environmental and climatic conditions over 3 years influence mosquito ecology across a socioeconomic gradient in Baltimore, MD. We show that decaying infrastructure and vegetation are important determinants of Ae. albopictus infestation. We demonstrate that both precipitation and vegetation influence mosquito production in ways that are mediated by the level of infrastructural decay on a given block. Mosquitoes were more common on blocks with greater abandonment, but when precipitation was low, mosquitoes were more likely to be found in higher-income neighborhoods with managed container habitat. Likewise, although increased vegetation was a negative predictor of mosquito infestation, more vegetation on blocks with high abandonment was associated with the largest mosquito populations. These findings indicate that fine spatial scale modeling of mosquito habitat within urban areas is needed to more accurately target vector control.