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mad cow thread
two useful articles
lancet Volume 354, Issue 9175 , 24 July 1999, Pages 317-323
Variant Creutzfeldt-Jakob disease
It is clear that the prion strain causing bovine spongiform
encephalopathy (BSE) in cattle has infected human beings, manifesting
itself as a novel human prion disease, variant Creutzfeldt-Jakob disease
(CjD). Studies of the incubation periods seen in previous epidemics of
human prion disease and of the effect of transmission barriers limiting
spread of these diseases between species, suggest that the early variant
CJD cases may have been exposed during the preclinical phase of the BSE
epidemic. It must therefore be considered that many cases may follow
from later exposure in an epidemic that would be expected to evolve over
decades. Since the number of people currently incubating this disease is
unknown, there are concerns that prions might be transmitted
iatrogenically via blood transfusion, tissue donation, and, since prions
resist routine sterilisation, contamination of surgical instruments.
Such risks remain unquantified. Although variant CJD can be diagnosed
during life by tonsil biopsy, a prion-specific blood test is needed to
assess and manage this potential threat to public health. The
theoretical possibility that BSE prions might have transferred to other
species and continue to present a risk to human health cannot be
excluded at present.
The AMA council report below are classic famous last words that should
remind the US public who not to beleive:
Risk of Transmission of Bovine Spongiform Encephalopathy to Humans in
the United States
Report of the Council on Scientific Affairs
Litjen Tan, PhD; Michael A. Williams, MD; Mohamed Khaleem Khan, MD, PhD;
Hunter C. Champion; Nancy H. Nielsen, MD, PhD; for the Council on
Scientific Affairs, American Medical Association
Context The risk of possible transmission of bovine spongiform
encephalopathy (BSE) in the United States is a substantial public health
Objective To systematically review the current scientific literature
and discuss legislation and regulations that have been implemented to
prevent the disease.
Methods Literature review using the MEDLINE, EMBASE, and Lexis/Nexis
databases for 1975 through 1997 on the terms bovine spongiform
encephalopathy, prion diseases, prions, and Creutzfeldt-Jakob syndrome.
The Internet was used to identify regulatory actions and health
Data Extraction MEDLINE, EMBASE, and Lexis/Nexis databases were
searched from 1975 through 1997 for English-language articles that
provided information on assessment of transmission risk.
Results Unique circumstances in the United Kingdom caused the emergence
and propagation of BSE in cattle, including widespread use of meat and
bonemeal cattle feed derived from scrapie-infected sheep and the
adoption of a new type of processing that did not reduce the amount of
infectious prions prior to feeding. Many of these circumstances do not
exist in the United States. In the United Kingdom, new variant
Creutzfeldt-Jakob disease probably resulted from the ingestion of
BSE-contaminated processed beef. The United Kingdom and the European
Union now have strong regulations in place to stop the spread of BSE.
While BSE has not been observed in the United States, the US government
has surveillance and response plans in effect.
Conclusions Current risk of transmission of BSE in the United States is
minimal because (1) BSE has not been shown to exist in this country; (2)
adequate regulations exist to prevent entry of foreign sources of BSE
into the United States; (3) adequate regulations exist to prevent
undetected cases of BSE from uncontrolled amplification within the US
cattle population; and (4) adequate preventive guidelines exist to
prevent high-risk bovine materials from contaminating products intended
for human consumption.
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