In sheep, scrapie is a fatal neurologic disease that is caused by a misfolded protein called a prion (designated PrPSc). The normal cellular prion protein (PrPC) is encoded by an endogenous gene, PRNP, that is present in high concentrations within the CNS. Although a broad range of functions has been described for PrPC, its entire range of functions has yet to be fully elucidated. Accumulation of PrPSc results in neurodegeneration. The PRNP gene has several naturally occurring polymorphisms, and there is a strong correlation between scrapie susceptibility and PRNP genotype. The cornerstone of scrapie eradication programs is the selection of scrapie-resistant genotypes to eliminate classical scrapie. Transmission of classical scrapie in sheep occurs during the prenatal and periparturient periods when lambs are highly susceptible. Initially, the scrapie agent is disseminated throughout the lymphoid system and into the CNS. Shedding of the scrapie agent occurs before the onset of clinical signs. In contrast to classical scrapie, atypical scrapie is believed to be a spontaneous disease that occurs in isolated instances in older animals within a flock. The agent that causes atypical scrapie is not considered to be naturally transmissible. Transmission of the scrapie agent to species other than sheep, including deer, has been experimentally demonstrated as has the transmission of nonscrapie prion agents to sheep. The purpose of this review is to outline the current methods for diagnosing scrapie in sheep and the techniques used for studying the pathogenesis and host range of the scrapie agent. Also discussed is the US scrapie eradication program including recent updates.
Since the September 11, 2001, terrorist attacks, concern for the future direction of biological research has expanded to include not only issues involving the welfare of mankind, but also the more immediate and personal concern of individual scientists in the life sciences community. For many investigators in the life sciences, the remainder of their careers will be impacted by concerns about bioterrorism and issues associated with dual-use research. Awareness of these issues will be critical for all professional groups and affiliated organizations as they navigate the growing call for more federal rules and regulations. Veterinarians are not immune to the coming changes in science; all researchers risk criminal sanctions if they violate the USA Patriot Act or the Bioterrorism Act of 2002. Compliance with these regulations will be necessary, not just because of the potential legal ramifications, but because establishing and maintaining public trust is a never-ending requirement for the future of scientific research.