1. The wild−domestic interface
Interfaces between populations are important in infectious disease epidemiology because they are spatiotemporal points of contact at which transmission of microbes between populations could occur, leading to spill-over events and potentially, the emergence of infectious diseases (Magouras et al., 2020). Understanding the characteristics of such interfaces, how contacts and microbe transmission occurs, and can be influenced is critical to prevent disease spread (Hassell et al., 2017).
The wildlife−domestic interface represents risks of transmission of microbes between wild and domestic animals. Because such interfaces involve domestic animals, they are usually anthropogenic, occurring when people and their activities encroach on wildlife habitat (for example, agriculture (Jori et al. (2021) or deurbanization (Ward et al., 2004)), people bring wildlife into built environments (for example, wildlife farming and markets; Brookes et al. (2022); Wikramanayake et al. (2021)), or wildlife become adapted to built environments (Bradley & Altizer, 2007).
Established wildlife−domestic interfaces for infectious disease spread include rabies virus between wild and domestic dog populations (Lushasi et al., 2021), Japanese encephalitis virus between waterbirds, pigs and poultry (Mulvey et al., 2021; Walsh et al., 2022), and tuberculosis between badgers and cattle (Chambers et al., 2014). These examples demonstrate the diversity of reservoir and other host species, as well as ecological landscapes in which interfaces occur. The need to understand interfaces involving wildlife and how disease transmission events occur has become more important over the previous few decades as increased anthropogenic pressure on wildlife populations and their habitats have intensified the risk of microbe transmission, resulting in increased frequency of emergence of infectious diseases (Cunningham et al., 2017). Recent – and well-defined – wildlife-domestic interfaces include those at which henipaviruses have emerged, including Hendra virus from bats to horses and Nipah virus from bats to pigs (Field et al., 2007); but there are also less well-defined or unknown interfaces in which a disease of animal origin might have arisen from wildlife with a domestic livestock or farmed wildlife intermediate. Examples of the latter include SARS and COVID-19 (SARS-CoV and SARS-coV2, respectively) in which wildlife and interfaces with farmed animals at markets are implicated but the specific interfaces (for example, which species were involved) are unknown (Shi & Hu, 2008; Worobey et al.).
Disease spread models can provide insights about the circumstances in which wildlife−domestic interfaces become important, and factors that could limit the transmission between populations at these interfaces. A critical limitation of such models is that they are dependent on adequate data to produce meaningful and useful predictions. Recent reviews demonstrate that the data required for such models or about specific interfaces can be limited (Brookes et al., 2022; Gabriele-Rivet et al., 2019). Defining such interfaces in terms of the species and pathogens involved, and the extent of the interface (for example, spatially and temporally, the abundance or density of species involved, and the prevalence of potential pathogens) are minimum requirements, but fundamental to useful models is quantification of the probability or rate of effective contact such that microbe transmission could occur between individuals.
In the following sections, we review the concepts of infectious disease epidemiology in the context of disease spread models, then illustrate the types of data required using the example of rabies modelling in northern Australia and the quantification of contacts that would be required to determine rabies spread between wild and domestic dog populations.