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About the Authors:
Justin J. Greenlee
* E-mail: [email protected]
Affiliation: National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, Ames, Iowa, United States of America
Jodi D. Smith
Affiliation: National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, Ames, Iowa, United States of America
M. Heather West Greenlee
Affiliation: Iowa State University, Ames, Iowa, United States of America
Eric M. Nicholson
Affiliation: National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, Ames, Iowa, United States of America
Introduction
Prion diseases or transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases that naturally affect several species including human beings. These chronic diseases are associated with the accumulation of a protease-resistant, disease-associated isoform of the prion protein (PrPSc) in the central nervous system and other tissues, depending on the species affected. In humans, TSEs can be acquired through exposure to infectious material, inherited as germline polymorphisms in the prion gene (prnp), or occur spontaneously.
Bovine spongiform encephalopathy (BSE), a TSE of cattle, can be subdivided into at least three groups: classical, H-type, and L-type. The latter 2 designations are based on higher or lower apparent molecular mass profiles of the unglycosylated PrPSc band in a western blot [1], [2], [3] and are collectively referred to as atypical BSE. The vast majority of BSE cases are the classical subtype that was associated with the UK BSE epizootic. Classical BSE has spread to several mammalian species including human beings [4], [5], [6] causing major animal health and public health concerns.
Epidemiological studies suggest that classical BSE is spread through contaminated feedstuffs, and early in the UK epizootic it was suspected that the origin of the disease was scrapie [7], [8], a TSE known to exist in sheep for over 200 years. However, experimental transmission of scrapie to cattle by a natural route has failed to produce disease, and while transmission of scrapie to cattle by the intracranial route produces a disease in cattle, it fails to accurately reproduce the clinical and pathologic features of BSE in cattle [9], [10]. Thus the origin of classical BSE remains unclear.
H-type BSE has been described in cattle from France [11], Germany [1], Japan [12], the Netherlands [13], Poland [14], Switzerland [15], the United Kingdom...