Modeling of Wildlife-Associated Zoonoses: Applications and Caveats

Abstract

Wildlife species are identified as an important source of emerging zoonotic disease. Accordingly, public health programs have attempted to expand in scope to include a greater focus on wildlife and its role in zoonotic disease outbreaks. Zoonotic disease transmission dynamics involving wildlife are complex and nonlinear, presenting a number of challenges. First, empirical characterization of wildlife host species and pathogen systems are often lacking, and insight into one system may have little application to another involving the same host species and pathogen. Pathogen transmission characterization is difficult due to the changing nature of population size and density associated with wildlife hosts. Infectious disease itself may influence wildlife population demographics through compensatory responses that may evolve, such as decreased age to reproduction. Furthermore, wildlife reservoir dynamics can be complex, involving various host species and populations that may vary in their contribution to pathogen transmission and persistence over space and time. Mathematical models can provide an important tool to engage these complex systems, and there is an urgent need for increased computational focus on the coupled dynamics that underlie pathogen spillover at the humanwildlife interface. Often, however, scientists conducting empirical studies on emerging zoonotic disease do not have the necessary skill base to choose, develop, and apply models to evaluate these complex systems. How do modeling frameworks differ and what considerations are important when applying modeling tools to the study of zoonotic disease? Using zoonotic disease examples, we provide an overview of several common approaches and general considerations important in the modeling of wildlife-associated zoonoses.

The Necrophagous Fly Anthrax Transmission Pathway: Empirical and Genetic Evidence from Wildlife Epizootics

“…Anthrax is reported nearly worldwide (Hugh-Jones 1999, Fasanella et al 2010, although the distribution of naturally occurring disease is limited by ecological factors (Blackburn 2010, Alexander et al 2012) and B. anthracis can be difficult to isolate from the environment. Outbreaks in the United States have been associated with wildlife, particularly white-tailed deer (Odocoileus virginanus) in southwest Texas (Blackburn and Goodin 2013), and elk (Cervus elaphus), plains bison (Bison bison bison), and white-tailed deer in southwestern Montana (Hugh-Jones and Blackburn 2009).…”

“…Outbreaks in the United States have been associated with wildlife, particularly white-tailed deer (Odocoileus virginanus) in southwest Texas (Blackburn and Goodin 2013), and elk (Cervus elaphus), plains bison (Bison bison bison), and white-tailed deer in southwestern Montana (Hugh-Jones and Blackburn 2009). Classically, it is hypothesized that herbivore exposure to B. anthracis is via ingestion of spores through grazing, browsing, or bloodsucking insect bites, particularly tabanid flies (Alexander et al 2012). Grazing animals ingest both vegetation and soil simultaneously or ingest large quantities of soil at certain times of year (Turner et al 2013).…”

Spatially explicit uncertainty modeling of zoonotic pathogen distribution: a case of Listeria monocytogenes in New York State, USA

“…Secondly, the transmission dynamics that involve wildlife are often complex and thus present a number of challenges (Alexander et al 2012). For instance, practical characterization of wildlife host species and pathogen systems is often lacking, and insight into one system may have little application to another involving the same host species and pathogen (Alexander et al 2012).…”

“…Secondly, the transmission dynamics that involve wildlife are often complex and thus present a number of challenges (Alexander et al 2012). For instance, practical characterization of wildlife host species and pathogen systems is often lacking, and insight into one system may have little application to another involving the same host species and pathogen (Alexander et al 2012). Usually, the process by which a zoonotic pathogen moves from an animal host to a human host is referred to as spillover and occurs as a result of complex bidirectional interactions among people, animals, pathogen communities, and environments, and is a key step in the zoonotic disease spread process (Alexander et al 2012).…”

“…For instance, practical characterization of wildlife host species and pathogen systems is often lacking, and insight into one system may have little application to another involving the same host species and pathogen (Alexander et al 2012). Usually, the process by which a zoonotic pathogen moves from an animal host to a human host is referred to as spillover and occurs as a result of complex bidirectional interactions among people, animals, pathogen communities, and environments, and is a key step in the zoonotic disease spread process (Alexander et al 2012). Each individual in the human population is not equally at risk for zoonotic pathogen and this can be proven using spatial disease models that show in which areas a particular pathogen thrives best depending on the factors that favor its survival.…”