Location: Virus and Prion ResearchTitle: Pathogenesis, detection, and control of scrapie in sheep
|CASSMAN, ERIC - Oak Ridge Institute For Science And Education (ORISE)|
Submitted to: American Journal of Veterinary Research
Publication Type: Review Article
Publication Acceptance Date: 12/15/2019
Publication Date: 7/1/2020
Citation: Cassman, E.D., Greenlee, J.J. 2020. Pathogenesis, detection, and control of scrapie in sheep. American Journal of Veterinary Research. 81(7):600-614. https://doi.org/10.2460/ajvr.81.7.600.
Technical Abstract: Sheep scrapie is a fatal neurologic disease that is caused by an infectious misfolded protein called a prion. The prion protein is encoded by an endogenous gene, PRNP, and it resides in high concentrations within the central nervous system. A broad range of functions for the prion protein have been uncovered, but the entire range of function is undetermined. In the misfolded conformation, prion accumulation results in neurodegeneration. There are several naturally occurring polymorphisms in the PRNP gene, and there is a strong correlation between disease susceptibility and the PRNP genotype. The cornerstone of many scrapie eradication programs is selection of scrapie resistant genotypes. The transmission of scrapie often occurs between sheep in the periparturient period when lambs are the most susceptible due to higher densities of gut-associated lymphoid tissue. Subsequently, prions are disseminated to the lymphoid system and spread to the central nervous system. The shedding of prions occurs prior to the onset of clinical signs. In contrast to classical scrapie, atypical scrapie is a spontaneous form of scrapie that occurs in individual older animals within a flock. It is not considered to be naturally infectious. This review addresses the current diagnostic modalities and techniques for studying scrapie in sheep. The examination of disease characteristics aims to identify the etiology and diagnose prion diseases. Scrapie transmission to other species including deer has been demonstrated experimentally, as well as the transmission of non-scrapie prion diseases to sheep. Finally, the effectiveness of the United States scrapie eradication program is reviewed.