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From: TSS (
Subject: Summary of the 84th SEAC meeting held on 28 September 2004
Date: October 5, 2004 at 6:26 am PST

-------- Original Message --------
Subject: Summary of the 84th SEAC meeting held on 28 September 2004.
Date: Mon, 4 Oct 2004 16:23:51 -0500
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy

##################### Bovine Spongiform Encephalopathy #####################

Summary of the 84th SEAC meeting held on 28 September 2004.


The Spongiform Encephalopathy Advisory Committee (SEAC) held its 84th
meeting in London on 28th September 2004, when it discussed the
following matters:


SEAC was presented with figures showing the annual number of BSE cases
in cattle in Great Britain (GB) since the 1980s and the reductions in
the number of cases after control measures had been introduced. The
figures were compared with data on BSE cases reported in other
countries. In GB, the BSE epidemic peaked in 1992, when over 36 500
cases were confirmed but thereafter, the number of cases declined
considerably. In GB, a total number of around 183 000 BSE cases had been
recorded to date. The committee was informed that 84 cases have been
reported in animals born after the introduction of the reinforced ban
(in 1996). Further research is being conducted to investigate such
cases. An estimate of future BSE cases in GB was also presented that
suggested an annual decline from around 285 cases in 2004 to around one
case in 2010.


SEAC was updated on the latest figures from the National CJD
surveillance unit. Up until September 2004, a total of 149 vCJD cases
have been confirmed in the UK, including five cases still alive. All
clinical vCJD cases tested to date are of the same genotype at codon 129
of the PrP gene (methionine homozygous). Short-term analysis of the
number of deaths from vCJD continues to show statistically-significant
evidence that the epidemic is no longer increasing exponentially and, at
least in the short term, the epidemic may have peaked.


The SEAC sheep subgroup recently considered the impact of a number of
options to breed TSE resistance into the national sheep flock as part of
a consultation on Defras National Scrapie Plan. SEAC was presented with
a statement from the subgroup summarising its conclusions. The subgroup
concluded that the current strategy to breed scrapie resistance into the
national flock remains appropriate but that it should be kept under
review. In addition, the most scientifically appropriate option for
breeding TSE resistance is a scheme close to the currently used Ram
Genotyping Scheme if employed on a compulsory basis. SEAC endorsed the
statement pending minor amendments to take into account a very recent
consideration of two additional options by the subgroup.


The FSA is reviewing its contingency policy should BSE ever be found
naturally occurring in sheep. To assist with this consideration, the FSA
commissioned two modelling studies to estimate the possible prevalence
of BSE in sheep and to estimate the likely impact of different risk
reduction strategies should BSE be found in sheep. SEAC was asked to
advise on the underlying scientific assumptions and approach adopted in
both studies, taking any uncertainties into account. SEAC noted the
theoretical nature of the work but agreed with the general approach
taken in both studies.

SEAC considered tests to distinguish BSE from scrapie had limitations
but were becoming more robust. The committee awaits the results of the
ongoing ring trial that may provide clarity on this issue.

SEAC concluded that the experimental studies to date showed no positive
evidence for BSE in sheep. However, modelling the maximum number of
possible cases based on these experimental data is limited by
assumptions made in such analyses. The committee noted that because of
the way some of the data used in the modelling had been collected, the
number of TSE cases that could be BSE may have been underestimated.

The committee acknowledged that modelling the possible impact of BSE in
sheep if it entered the national flock was complex and difficult, and
because of the very limited data available the models had necessarily
relied heavily on many assumptions. In particular, the modelling had
assumed that BSE and scrapie would behave similarly in all types of
sheep, which is largely unknown. However, the committee did accept that
the modelling indicated a high potential risk of human infection should
BSE enter the national flock.

SEAC considered the impact of the risk reduction strategies presented
and agreed that a strategy based on prion protein genotype would be the
most effective.


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