Juxtaposition between host population structures: implications for disease transmission in a sympatric cervid community

Ryan K. Brook,David W. Coltman,Eric Vander Wal,Erin Bayne,José A. Andrés,Paul C. Paquet,Iain Edye

doi:10.1111/eva.12065

Abstract

Sympatric populations of phylogenetically related species are often vulnerable to similar communicable diseases. Although some host populations may exhibit spatial structure, other hosts within the community may have unstructured populations. Thus, individuals from unstructured host populations may act as interspecific vectors among discrete subpopulations of sympatric alternate hosts. We used a cervid-bovine tuberculosis (Mycobacterium bovis) system to investigate the landscape-scale potential for bovine tuberculosis transmission within a nonmigratory white-tailed deer (Odocoileus virginianus) and elk (Cervus canadensis) community. Using landscape population genetics, we tested for genetic and spatial structure in white-tailed deer. We then compared these findings with the sympatric elk population that is structured and which has structure that correlates spatially and genetically to physiognomic landscape features. Despite genetic structure that indicates the white-tailed deer population forms three sympatric clusters, the absence of spatial structure suggested that intraspecific pathogen transmission is not likely to be limited by physiognomic landscape features. The potential for intraspecific transmission among subpopulations of elk is low due to spatial population structure. Given that white-tailed deer are abundant, widely distributed, and exhibit a distinct lack of spatial population structure, white-tailed deer likely pose a greater threat as bovine tuberculosis vectors among elk subpopulations than elk.

Highlights

One of the key goals of disease ecology is to understand pathogen transmission and disease spread over space and time (Tompkins et al 2011)
Study area In southwestern Manitoba, Canada, the Boreal Plains ecoregion (Bailey 1968) transitions into the Prairie ecoregion (Olson et al 2001). This area includes the Riding Mountain region, which is comprised of Riding Mountain National Park (RMNP; 3000 km2) and the Duck Mountain Provincial Park and Forest (DMPP&F; 3800 km2) (Fig. 1)
We examined the genetic differentiation of white-tailed deer using nonmodel-based approaches comparable to those previously used in the juxtaposed population of elk (Vander Wal et al 2012)

Summary

Introduction

One of the key goals of disease ecology is to understand pathogen transmission and disease spread over space and time (Tompkins et al 2011). In many cases, pathogens are not species-specific and pathogen transmission is a multi-host community-level phenomenon (Rigaud et al 2010). Ignoring the interactions among different members of the host community greatly limits our ability to estimate different epidemiological parameters (McCoy et al 2003; Johnson and Thieltges 2010; Searle et al 2011). Identifying the relative contributions of different host species, their interactions, and environmental characteristics in overall transmission heterogeneity is clearly needed (Paull et al 2012). Studying multi-host endemic disease systems is often complicated because they commonly involve highly mobile and widely distributed wildlife species with low prevalence of infection [e.g., chronic wasting disease, CWD and bovine tuberculosis, Mycobacterium bovis, bTB (Conner et al 2008)].

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