Harvest increase and culling as tools for managing chronic wasting disease in white-tailed deer: Data and code

<p>Chronic wasting disease (CWD), a transmissible spongiform encephalopathy that affects white-tailed deer (<i>Odocoileus virginianus</i>) and other cervids, is increasing in geographic distribution and prevalence. Because the spread of CWD will cause white-tailed deer populations to decline, wildlife management agencies are seeking effective strategies to mitigate CWD spread. Areas where hunters can harvest more deer (i.e., CWD management zones) and removal of symptomatic or asymptomatic deer from locations where CWD has been detected (i.e., post-harvest targeted culling) are two CWD management strategies currently in use. However, it is unclear how factors such as the geographic location where CWD is introduced, the age and sex of the deer that introduce CWD, the geographic location and extent of CWD management zones, harvest within CWD management zones, and post-harvest targeted may affect the establishment and spread of CWD in a region. Our objective was to determine how such factors impact the effectiveness of CWD management zones and post-harvest targeted culling in northwest Indiana and northeast Illinois, USA. We simulated a CWD outbreak in a realistic model-generated deer population using the <i>Ov</i>CWD modeling framework. We found that CWD introduction location and age-sex class of the deer that introduce CWD had the largest effect on the CWD fadeout probability and geographic spread of CWD. The CWD management zone that encompassed 2,352 km<sup>2</sup> increased the CWD fadeout probability and decreased the geographic spread of CWD more than the CWD management zones that encompassed 976 km<sup>2</sup> or 532 km<sup>2</sup>. Increasing harvest by ≥200% within the largest CWD management zone resulted in a greater CWD fadeout probability and less geographic spread of CWD. Post-harvest targeted culling in combination with a CWD management zone also produced a greater CWD fadeout probability and less geographic spread of CWD. The CWD fadeout probability increased and geographic spread of CWD decreased with increasing percentage of deer tested for CWD and percentage of deer removed during culling. Our results demonstrate the importance of disease introduction location and the demographics of the deer that introduce disease when simulating CWD outbreaks using agent-based models. Our simulations also demonstrate that increases in harvest and culling must be greater than those currently in use by wildlife management agencies to slow the spread of CWD. Although control of CWD using the strategies simulated may be epidemiologically possible, such management may be intractable given current levels of deer hunter participation and desire to harvest more deer. These findings provide decision makers with information needed to determine the feasibility of CWD management strategies.</p>