Ovine and Caprine Scrapie Study Guide

Overview and Clinical Importance

Scrapie is a fatal, progressive neurodegenerative disease affecting sheep and goats, classified as a transmissible spongiform encephalopathy (TSE). It is caused by abnormal prion proteins (PrPSc) that induce misfolding of normal cellular prion proteins (PrPC). First described in 1732 in Great Britain, scrapie represents the oldest known prion disease and serves as the prototype for understanding all TSEs, including bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease (CJD) in humans.

Scrapie is a federally reportable disease in the United States. The National Scrapie Eradication Program (NSEP) has been highly successful, reducing prevalence by 99% since surveillance began in 2003. Understanding scrapie is essential for NAVLE as it tests knowledge of prion biology, genetic susceptibility, clinical recognition, and regulatory implications.

Etiology and Pathogenesis

The Prion Protein

Prions (proteinaceous infectious particles) are unique infectious agents that contain no nucleic acids (DNA or RNA). The normal cellular prion protein (PrPC) is encoded by the PRNP gene and is found in high concentrations in neurons and lymphoid tissues. The precise function of PrPC remains unclear but may include roles in myelin maintenance, copper binding, and neuroprotection.