CWD can be confirmed through laboratory analysis of central (obex, spinal cord) or peripheral (retropharyngeal lymph node, tonsil, rectal mucosa associated lymphoid tissue) nervous system tissue. Tissue samples can be obtained by anesthetizing live animals and obtaining a biopsy of tonsil or rectal mucosa associated lymphoid tissue (Wolfe et al. 2002, 2007) or from necropsying carcasses. Current screening tests include enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (Spraker et al. 2002), though other prion amplification methods are being evaluated (Wyckoff et al. 2015). Immunohistochemistry is currently the most reliable test for detecting CWD in animal tissues. However, it is still an imperfect test and a negative test result does not guarantee a CWD-free animal, particularly early in the disease course (Fox et al. 2006, Wolfe et al. 2007). Furthermore, pathogenesis of CWD may differ among deer and elk and within species based on composition of the prion precursor gene, especially with regards to the timing of misfolded prion deposition in different tissues (Keane et al. 2009, Spraker et al. 2009, Wolfe et al. 2014). These differences reduce the ability to detect CWD early in the disease course.