Urbanization and Disease Emergence: Dynamics at the Wildlife-Livestock-Human Interface

Abstract

Urbanization is characterized by rapid intensification of agriculture, socioeconomic change, and ecological fragmentation, which can have profound impacts on the epidemiology of infectious disease. Here, we review current scientific evidence for the drivers and epidemiology of emerging wildlife-borne zoonoses in urban landscapes, where anthropogenic pressures can create diverse wildlife-livestock-human interfaces. We argue that these interfaces represent a critical point for cross-species transmission and emergence of pathogens into new host populations, and thus understanding their form and function is necessary to identify suitable interventions to mitigate the risk of disease emergence. To achieve this, interfaces must be studied as complex, multihost communities whose structure and form are dictated by both ecological and anthropological factors.

Keywords: disease emergence; interface; urbanization; wildlife.

Figure 1

Conceptual Framework for Disease Emergence in Urban Landscapes (adapted, with permission, from 34, 38). It should be noted that we consider the structure of this framework as applicable to the emergence of antimicrobial resistance, as it is to disease emergence . (A) This framework incorporates urban land-use change and its effects on two spatial scales: at a systems and local level. A simplified disease reservoir framework is included at the local level, in which livestock and synanthropic wildlife exist within the maintenance community as maintenance hosts (populations within the reservoir that can maintain the pathogen) or non-maintenance hosts (populations within the reservoir that cannot maintain the pathogen, therefore acting as vectors), or as bridge hosts that exist outside the maintenance community. (B) Following , spillover, which in this framework can relate to pathogen transfer in all directions except for target to reservoir, is governed by the force of infection consisting of the three elements shown.

Figure 2

Cascades of Abiotic Factors, and the Components of Host–Pathogen Biotic System (for a Directly Transmitted Pathogen) That Are Affected by These Factors, Are Represented on Either Side of a Hypothetical Wildlife–Human Interface. Biotic systems represented here include a multihost wildlife community (acting as a parasite reservoir and composed of maintenance and non-maintenance hosts, and nonsusceptible species with direct ecological interactions with the reservoir), a human community (acting as variably susceptible target hosts) and the community of parasites within the wildlife reservoir. The requirements for spillover are represented centrally at the interface.