Research Project: Transmission,
Differentiation, and Pathobiology of Transmissible Spongiform
Encephalopathies
Location: Virus and Prion Diseases of Livestock
Identification and Characterization of U.S. BSE
Cases
Authors
Hall, S - USDA, APHIS, VS, NVSL
Richt, Juergen
Davis, A - USDA, APHIS, VS, NVSL
Kluge, J - USDA, APHIS, VS, NVSL
Simmons, M - VETERINARY LABS AGENCY,UK
Stack, M - VETERINARY LABS AGENCY,UK
Spencer, Y - VETERINARY LABS AGENCY,UK
Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: April 25, 2006
Publication Date: May 28, 2006
Citation: Hall, S.M., Richt, J., Davis, A., Kluge, J., Simmons, M., Stack,
M., Spencer, Y. 2006. Identification and characterization of U.S. BSE cases
[abstract]. Prion Diseases of Domestic Livestock. p. 25.
Technical Abstract: Bovine Spongiform Encephalopathy (BSE) surveillance has
been ongoing in the USA since the early 1990¿s and initial testing was done
at the USDA, National Veterinary Services Laboratories (NVSL) utilizing
routine histopathology exclusively. In 1995, the immunohistochemistry (IHC)
test was incorporated into surveillance testing in addition to routine
histopathology. By 1999 virtually all BSE screening was performed by IHC and
by 2001 the NVSL had switched to an automated IHC procedure. In 2002 and
2003 the NVSL tested about 20,000 high risk animals each year by IHC. In
December, 2003 an animal was identified by IHC as positive for BSE (Case 1);
this animal was determined to be imported from Canada. After this animal was
identified, in June 2004 the USDA began its enhanced surveillance program as
a shared effort between selected state veterinary diagnostic laboratories
and NVSL, as part of the National Animal Health Laboratory Network. The plan
called for testing as many targeted high risk animals as possible in a 12-18
month period. From June 1, 2004 through March 21, 2006, over 650,000 animals
have been tested (Bio-Rad ELISA). Of those tested, two animals (Cases 2 and
3) have been identified as positive for BSE. While all three cases were
strongly positive by Bio-Rad ELISA, Cases 2 and 3 have common features which
are distinct from Case 1. Definitive spongiform changes in the obex, strong
immunohistochemical reactions, and Western blot patterns similar to European
BSE cases were observed in Case 1. In contrast, Cases 2 and 3 did not
contain definitive histological lesions of BSE and the IHC staining was less
intense than Case 1. In addition, Cases 2 (approximately 12 years) and Case
3 (approximately ten years) were older animals while Case 1 was 6.5 years
old. Western blot analysis, PrP**Sc from Case 1 showed molecular features
similar to typical BSE isolates, whereas PrP**Sc from Cases 2 and 3 revealed
an unusual molecular PrP**Sc pattern: molecular mass of the unglycosylated
and monoglycosylated isoform was higher than that of typical BSE isolates.
Case 1 contained more PrP**Sc per brain tissue mg equivalent compared with
Cases 2 and 3 using antibody 6H4. In Western Blot analysis, Case 2 and Case
3 were strongly positive with antibody P4, while Case 1 was negative or
weakly positive with P4.
http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=194279