Resource provisioning and infectious disease dynamics in urban environments

Background/Question/Methods

Urbanization is increasing globally. A major concern in the coming decades will be how wildlife use of urban habitats affects the spread of infectious diseases. One way that urbanization can drive changes in disease dynamics is through resource provisioning, as wildlife living in cities can experience shifts in diet quality and the spatio-temporal distribution of resources. These changes can affect two key processes important for infectious disease spread:  (1) host susceptibility, as might be driven by changes in host microbiota and immune defense, and (2) host exposure to pathogens, as could be driven by changes in host movement, aggregation and interspecific contacts. This talk provides a conceptual framework to examine how human-driven changes in resources interact with the dynamics of wildlife diseases. We characterize the range of outcomes on disease dynamics in urban environments through a meta-analysis of existing studies and outline a modeling framework that can capture the net effect of synergistic and opposing mechanisms. We further illustrate how these mechanisms might operate on a model avian host system that has recently become abundant in urban parks, where individuals experience extreme dietary changes and are exposed to novel infectious agents.

Results/Conclusions

Several recent case studies demonstrate that resource provisioning can alter infectious disease dynamics in urban wildlife. Our survey revealed a continuum of effects, from cases where resource shifts lowered the prevalence of complex life cycle parasites in urban predators, to cases where predictable and aggregated resources in cities increased host exposure to pathogens. We also found support for key mechanisms by which provisioning in urban areas influences disease processes, including demographic, behavioral and immune defense effects. Early results from work on the model avian-pathogen system indicates that birds inhabiting cities become accustomed to regular and frequent food provisioning by people, encounter more peridomestic species while foraging, and have a higher prevalence of novel gut pathogens than those that forage in natural areas. Collectively, these results are consistent with the idea that urban landscapes can affect wildlife disease dynamics through changes in resources, and demonstrate that supplemental resources can facilitate disease emergence by bringing humans, domesticated animals, and wildlife into close contact. We conclude by identifying gaps that require further exploration, including asking how dietary shifts influence the host microbiome and underlying host susceptibility to infection, and understanding the effects of urbanization on pathogen evolution.