Such transmissions have been most thoroughly documented for the mammalian PrP-based prion diseases, including Creutzfeldt-Jakob disease (CJD) and GSS [9] in humans, chronic wasting disease (CWD) in cervids, scrapie in sheep and goats, and bovine spongiform encephalopathy (BSE) [10]. This evidence concerns the gene PRNP and prion disease.