Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2009
Publication Date: 7/1/2009
Publication URL: http://ddr.nal.usda.gov/dspace/bitstream/10113/33943/1/IND44241920.pdf
Citation: Loiacono, C.M., Thomsen, B.V., Hall, S.M., Kiupel, M., Sutton, D., Orourke, K.I., Barr, B., Anthenill, L., Collins, J., Keane, D. 2009. Nor98 scrapie identified in the United States. Journal of Veterinary Diagnostic Investigation. 21(4):454-463. Interpretive Summary: Scrapie is a fatal degenerative brain disease of sheep and goats. The disease is found in most sheep producing areas of the world and is the subject of active eradication programs. Diagnosis of the disease is based on detection of an abnormally folded protein, the prion protein, in lymphoid tissues and brain of infected sheep. The abnormal prion protein is formed from the animal's native cellular prion protein, a normally folded form of the same protein strand. Diagnostic methods distinguish between the normal and abnormal protein through a variety of enzymatic and antibody-based detection methods. The novel scrapie strain identified as Nor98 is widely reported in European countries conducting large scale surveillance for scrapie. Nor98 prions are biochemically distinct from the prions in classical scrapie and distributed in novel patterns in the brain. This manuscript describes the first six cases of Nor98-like scrapie identified in US sheep, including a description of the diagnostic methods and laboratory findings in those cases.
Technical Abstract: The transmissible spongiform encephalopathies of domestic livestock are fatal neurodegenerative disorders characterized by accumulation of an abnormal isoform of the host prion protein in brain. Scrapie is the prion disease of sheep and the abnormal protein usually accumulates in lymphoid tissues months to years before the brain is affected. Early diagnosis is therefore based on antemortem or postmortem sampling of lymphoid tissues. In an effort to control the zoonotic prion disorder of cattle, large scale surveillance of slaughter sheep is conducted in many European countries. This effort has resulted in reports of novel scrapie strains characterized by differences in tissue distribution, biochemical characteristics, genetic resistance and epidemiology. The Nor98 strain, first identified in sheep in Norway in 1998, is now known to be widespread in the European sheep producing areas. Nor98 is typically identified in aged, clinically normal sheep presented for slaughter, although the appearance of clinical signs is noted in a small number of cases. The abnormal prion protein accumulates in areas of the brain typically spared in classical scrapie and is not found in lymphoid tissues. The abnormal prion protein is often sparsely distributed and diagnosis can be challenging. In this manuscript. six cases of Nor98 in US sheep are presented. Information on the cases includes flock history when known, clinical findings, histopathology results, abnormal prion protein distribution, and biochemical characterization of the prion protein by western blot analysis. The cases are remarkably similar to the reported European cases, suggesting a similar etiology.