Bovine Spongiform Encephalopathy: what is "Atypical BSE" and can we detect it?

Authors: Richt, Juergen

Submitted to: United States Animal Health Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2006
Publication Date: 10/12/2006
Citation: Richt, J.A. 2006. Bovine spongiform encephalopathy: what is "atypical BSE" and can we detect it [abstract]? United States Animal Health Association. p. 730.

Interpretive Summary:

Technical Abstract: Transmissible spongiform encephalopathy (TSE) agents induce fatal neurodegenerative diseases in humans and in some other mammalian species. Human TSEs include Creutzfeldt–Jakob disease (CJD), Gerstmann-Sträussler-Scheinker (GSS) syndrome, Kuru and Fatal Familial Insomnia (FFI). In animals, several distinct TSE diseases are recognized: scrapie in sheep and goats, transmissible mink encephalopathy (TME) in mink, chronic wasting disease (CWD) in cervids, and bovine spongiform encephalopathy (BSE) in cattle. BSE was first detected in 1986 in the United Kingdom and is the most likely cause of variant CJD in humans. BSE in cattle is a neurological disease with a characteristic molecular pattern of the protease-resistant prion protein, PrP**res. This BSE 'signature' has also been identified in BSE-induced TSEs of both domestic cats and exotic ruminant species. Since 2004, some cases of prion diseases in cattle have been described which show unusual or atypical features as assessed by the molecular characterization of PrP**res and/or histopathology, when compared to the unique features of previously described BSE. These atypical BSE cases have been characterized by Western blot and have been referred to as H- (i.e., high molecular weight) or L-type (i.e., low molecular weight type). These atypical BSE cases have been found mainly in cattle older than 8 years. In the U.S., three cases of BSE have been diagnosed so far. Case 1 represented a typical BSE isolate, identified in an animal imported from Canada. Cases 2 and 3 were identified in animals raised in the U.S. and revealed an unusual molecular PrP**res pattern, consistent with atypical BSE cases described as H-type in Europe. It should be noted that the Western Blot method applied for BSE confirmatory tests in the U.S. has been able to detect both H-type and L-type BSE cases when using known positive European samples.