Chronic Wasting Disease Drives Population Decline of White-Tailed Deer

PLoS One. 2016 Aug 30;11(8):e0161127. doi: 10.1371/journal.pone.0161127. eCollection 2016.

Abstract

Chronic wasting disease (CWD) is an invariably fatal transmissible spongiform encephalopathy of white-tailed deer, mule deer, elk, and moose. Despite a 100% fatality rate, areas of high prevalence, and increasingly expanding geographic endemic areas, little is known about the population-level effects of CWD in deer. To investigate these effects, we tested the null hypothesis that high prevalence CWD did not negatively impact white-tailed deer population sustainability. The specific objectives of the study were to monitor CWD-positive and CWD-negative white-tailed deer in a high-prevalence CWD area longitudinally via radio-telemetry and global positioning system (GPS) collars. For the two populations, we determined the following: a) demographic and disease indices, b) annual survival, and c) finite rate of population growth (λ). The CWD prevalence was higher in females (42%) than males (28.8%) and hunter harvest and clinical CWD were the most frequent causes of mortality, with CWD-positive deer over-represented in harvest and total mortalities. Survival was significantly lower for CWD-positive deer and separately by sex; CWD-positive deer were 4.5 times more likely to die annually than CWD-negative deer while bucks were 1.7 times more likely to die than does. Population λ was 0.896 (0.859-0.980), which indicated a 10.4% annual decline. We show that a chronic disease that becomes endemic in wildlife populations has the potential to be population-limiting and the strong population-level effects of CWD suggest affected populations are not sustainable at high disease prevalence under current harvest levels.

MeSH terms

  • Animals
  • Animals, Wild
  • Deer
  • Female
  • Male
  • Mortality
  • Population Density
  • Prevalence
  • Remote Sensing Technology / methods*
  • Wasting Disease, Chronic / epidemiology*

Grant support

This work was primarily supported by the Morris Animal Foundation (www.morrisanimalfoundation.org) through grant numbers: Established Investigator = D07ZO-159 (TEC, DRE, MJK, FGL, WEC, and TJK), and Fellowship Training Grant = D07ZO-425 (funded DRE's graduate research stipend). The United States Geological Survey (www.usgs.gov), Wyoming Game and Fish Department (https://wgfd.wyo.gov), and International Association of Fish and Wildlife Agencies (www.fishwildlife.org) each jointly funded parts of this work through grant number 000679 over multiple years (TEC, TJK, and DRE). The Wyoming Wildlife/Livestock Disease Research Partnership (http://wyagric.state.wy.us/divisions/ts/sections-a-programs/wildlifelivestock-disease-research) partially funded this work through project number 5-35466 (TEC, FGL, DRE, and TJK). Whitetails Unlimited (www.whitetailsunlimited.com) also provided some support (no grant number; TEC, FGL, DRE, and TJK), and National Cattleman’s Beef Association. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.