PROJECT SUMMARY Chronic wasting disease (CWD) is an emergent highly transmissible prion disease of cervids (deer, elk). The zoonotic threat to domestic animal species and humans CWD represents remains poorly understood. A prominent feature of CWD is abundant shedding of prions in secretions and excretions, thereby facilitating exposure of animals and humans by either direct and/or indirect/environmental contact. Prions avidly bind to many surfaces, including plant, metal, and soil constituents, and appear to remain infectious, thus leading to cumulative persistence in the environment. However, little is known about the impact and zoonotic transmission risk represented by shed CWD prions. The long-term goal of this research is to understand the prion/environment interface and thereby develop effective mitigation strategies to reduce both the spread of CWD and the direct and indirect exposure to humans. The central hypothesis for this work is that the robust transmission of CWD reflects a unique convergence of florid prion shedding and avid prion binding to soil constituents, thereby enhancing environmental persistence and bioavailability. To test this hypothesis we propose the following specific aims: Aim 1 will determine the amplitude and temporal shedding profile of CWD prions from the natural cervid host. Almost surely, shedding of prions into the environment contributes to long-term maintenance of CWD infection in natural settings. We will longitudinally quantify the level of prions in excreta of CWD infected deer to determine the magnitude of the CWD prion load introduced into the environment by infected animals. Aim 2 will define the distribution of CWD prions in simulated and naturally contaminated environments. While prions have been shown to bind to soil and remain infectious, to date means to directly detect CWD prions in the environment are still lacking. The results will determine where CWD prions are located in the environment. Aim 3 will define the factors that control prion bioavailability in the environment. It is not known how this avid binding affects prion stability, survival, and infectivity in the presence of environmental degradation processes. The results of this aim will determine whether (or not) soil binding enhances CWD transmission. These studies will: (1) Enable more targeted strategies to mitigate the spread and potential risks of this emerging uncontrolled prion disease in free-ranging animals; (2) Provide insight regarding the interfaces wherein inter-species CWD prion transmission could occur; and (3) Determine the practical consequences of prion binding to environmental constituents.