Fine-scale variation in microclimate across an urban landscape changes the capacity ofAedes albopictusto vector arbovirus

Abstract

Most statistical and mechanistic models used to predict mosquito borne disease transmission incorporate climate drivers of disease transmission by utilizing environmental data collected at scales that are potentially coarser than what mosquito vectors actually experience. Temperature and relative humidity can vary greatly between indoor and outdoor environments, and can be influenced strongly by variation in landscape features. In the Aedes albopictus system, we conducted a proof-of-concept study in the vicinity of the University of Georgia to explore the effects of fine-scale microclimate variation on mosquito life history and vectorial capacity (VC). We placed Ae. albopictus larvae in artificial pots distributed across three replicate sites within three different land uses – urban, suburban, and rural, which were characterized by high, intermediate, and low proportions of impervious surfaces. Data loggers were placed into each larval environment and in nearby vegetation to record daily variation in water and ambient temperature and relative humidity. The number of adults emerging from each pot and their body size and sex were recorded daily. We found mosquito microclimate to significantly vary across the season as well as with land use. Urban sites were in general warmer and less humid than suburban and rural sites, translating into decreased larval survival, smaller body sizes, and lower per capita growth rates of mosquitoes on urban sites. Dengue transmission potential was predicted to be higher in the summer than the fall. Additionally, the effects of land use on dengue transmission potential varied by season. Warm summers resulted in a higher predicted VC on the cooler, rural sites, while warmer, urban sites had a higher predicted VC during the cooler fall season.

Transmission of West Nile and other temperate mosquito-borne viruses peaks at intermediate environmental temperatures

“…We hypothesize that temperature variation over time and across microclimates may sustain transmission in regions with low or high mean summer temperatures by providing time windows suitable for transmission [35,36,38]. The temperature-dependent models also predict the seasonality of human cases of WNV, EEEV, and SLEV (Fig 9).…”

“…We use R0 as a static, relative metric of temperature suitability for transmission that incorporates the nonlinear effects of temperature on multiple traits [1,34] and is comparable across systems, rather than focusing on its more traditional interpretation as a threshold for disease invasion into a susceptible population. Temperature variation creates additional nonlinear effects on transmission [35][36][37][38] that are not well-captured by R0, [9,33,39-41] but could be incorporated in future work by integrating the thermal performance curves fit here over the observed temperature regime.…”

The Fine-Scale Landscape of Immunity and Parasitism in a Wild Ungulate Population

“…Parasite infection in the wild is extremely spatially heterogeneous. The scale at which spatial variation acts depends on the host and parasite being studied, and even fine-scale environmental heterogeneity may influence the spatial epidemiology of human diseases (Murdock et al 2017). However, the spatial ecology of disease is most often considered in terms of large-scale patterns (e.g.…”

“…An understanding of spatial processes is therefore crucial for designing public health interventions (Caprarelli and Fletcher 2014) and sampling regimes (Nusser et al 2008;Vidal-Martínez et al 2010;Lachish and Murray 2018). A deeper understanding of fine-scale spatial variation in disease processes could also inform patterns seen over wider distances (Murdock et al 2017;Pawley and McArdle 2018). In addition, if immunity and parasitism vary over short distances, infection-oriented studies of wild populations could be affected by greater degrees of spatial dependence than previously considered, which can affect inference.…”

The fine-scale landscape of immunity and parasitism in a wild ungulate population

“…In this context, our results have several important general implications. Firstly, fine-scale trends like those exhibited here may scale up quickly, contributing to larger-scale geographic patterns of disease that are more commonly studied (Ostfeld et al 2005;Murdock et al 2017;Murray et al 2018). Second, disease ecology studies that do not consider spatial autocorrelation, even over short distances, may be missing important sources of variation in immunity and exposure and risk reporting biased effect estimates.…”