CWD has also been detected in USA in areas far from the original endemic area and raised several questions: Whether the infectivity has been transported to these areas illegally in the form of tainted materials or infected animals or by some another way, whether the scrapie agent has adapted to cause CWD by repeated natural passages into the deer, or if the PrPC conversion in cervids is proficient enough to result in the sporadic emergence of the disease, which may in turn establish the epidemic by horizontal transmission. This evidence concerns the gene PRNP and scrapie.