Abstract
ABSTRACT Chronic-wasting disease (CWD) is a prion-derived fatal neurodegenerative disease that has affected wild cervid populations on a global scale. Susceptibility has been linked unambiguously to several amino acid variants within the prion protein gene (PRNP). Quantifying their distribution across landscapes can provide critical information for agencies attempting to adaptively manage CWD. Here we attempt to further define management implications of PRNP polymorphism by quantifying the contemporary geographic distribution (i.e., phylogeography) of PRNP variants in hunter-harvested white-tailed deer (WTD; Odocoileus virginianus, N = 1433) distributed across Arkansas (USA), including a focal spot for CWD since detection of the disease in February 2016. Of these, PRNP variants associated with the well-characterized 96S non-synonymous substitution showed a significant increase in relative frequency among older CWD-positive cohorts. We interpreted this pattern as reflective of a longer life expectancy for 96S genotypes in a CWD-endemic region, suggesting either decreased probabilities of infection or reduced disease progression. Other variants showing statistical signatures of potential increased susceptibility, however, seemingly reflect an artefact of population structure. We also showed marked heterogeneity across the landscape in the prevalence of ‘reduced susceptibility’ genotypes. This may indicate, in turn, that differences in disease susceptibility among WTD in Arkansas are an innate, population-level characteristic that is detectable through phylogeographic analysis.
Highlights
Chronic wasting disease (CWD) is a fatal neurodegenerative disorder that affects white-tailed 26 deer (WTD; Odocoileus virginianus) and related cervids[1,2], with severe impacts on native wildlife, that reverberate economically for recreational hunting and ancillary commercial 28 enterprises[3,4]
Endemic areas: Do ‘reduced susceptibility’ variants have an effect on survivorship? If so, does this leave a detectable signature of biased fitness? What are the impacts of prion protein gene (PRNP) polymorphism on population demographics? We address these questions at two spatial scales: 1) within a dense sampling of 68 the CWD-focal area (Newton County, Arkansas) from which prevalence, and, presumably, measurable impacts on population demography are highest; and 2) state-wide, where sampling
204 Conclusion Our results corroborate previous research conducted with white-tailed deer (WTD) in Illinois and Wisconsin: 206 reduced CWD susceptibility in PRNP variants associated with the non-synonymous 96S mutation[30,31]
Summary
Chronic wasting disease (CWD) is a fatal neurodegenerative disorder that affects white-tailed 26 deer (WTD; Odocoileus virginianus) and related cervids[1,2], with severe impacts on native wildlife, that reverberate economically for recreational hunting and ancillary commercial 28 enterprises[3,4]. Most CWD eradication efforts have proven unsuccessful far[5], leading to its continued spread and increased prevalence[6]. Several factors have impeded the eradication of CWD, including aspects of life history in both host and agent, as well as limited knowledge with regards to how these interact with 34 environment to define CWD epidemiology. The efficiency with which this occurs, coupled with an extensive incubation period[10], serve to confound proactive surveillance and management
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