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From: TSS ()
Subject: The Spongiform Encephalopathy Advisory Committee held its 86th meeting in London on 3rd March 2005
Date: March 8, 2005 at 1:16 pm PST

-------- Original Message --------
Subject: The Spongiform Encephalopathy Advisory Committee held its 86th meeting in London on 3rd March 2005
Date: Mon, 7 Mar 2005 09:16:45 -0600
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy

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

The Spongiform Encephalopathy Advisory Committee held its 86th
meeting in London on 3rd March 2005, when it discussed the
following matters:
Projections of the profile of the vCJD epidemic based on data from
clinical vCJD cases to date have suggested the number of
additional cases may be relatively small. However, recent
experimental and epidemiological findings have suggested that the
nature of the epidemic might be more complex and that there may
be individuals who are carriers of infectivity but who do not
necessarily develop clinical disease. Furthermore, potential
human to human infection via medical procedures (e.g. use of
contaminated surgical instruments or blood) might influence the
profile of the epidemic such that, if appropriate intervention is not
taken, a self-sustaining epidemic could arise.
SEAC conducted an initial consideration of the new information
and received papers and presentations from a number of leading
experts. The committee recognised that a survey of abnormal
prion protein in human tonsil and appendix samples suggests that
the prevalence of BSE infection in humans might be somewhat
higher than predicted from the clinical case data alone. Research
using mice carrying different forms of the human prion protein
gene indicates that the susceptibility to, and characteristics of,
BSE infection such as incubation period, may be influenced by the
form of prion protein gene individuals carry. Information about
Kuru, a human prion disease of cannibals in Papua New Guinea,
supports this suggestion. New epidemiological evidence suggests
that younger people might be relatively more susceptible to
infection. However, the age of greatest susceptibility is unclear.
SEAC agreed that further epidemiological analysis and modelling
work is required to comprehensively reassess the nature and
future profile of the vCJD epidemic. The committee tasked the
SEAC Epidemiology Subgroup to conduct this assessment taking
into account the new research and the possibility of human to
human infection. The subgroup was also asked to identify critical
factors that could influence the nature of the epidemic, and to
consider the likelihood of a self-sustaining epidemic and key
interventions which might prevent this. The subgroup will report its
considerations to SEAC at a future meeting.
Defra recently commissioned Professor William Hill, as an
independent advisor, to consider possible causes of BSE cases
born after the 1996 UK reinforced animal feed ban (known as
BARB cases). Professor Hill asked SEAC to identify issues that
should be considered as part of his report. The committee
identified a number of key areas for investigation. These included
assessment of data on BSE cases in other countries, possible
genetic relationships between BARB cases, and possible
environmental causes such as the mineral content of grazing
pastures or the presence of toxic alkaloids in feed. SEAC will
consider Professor Hills completed report at a future meeting.
Following the recent finding of possible BSE in a UK goat which
died in 1990, Defra and FSA asked SEAC for its view on further
research and the current level of risk in relation to consumption of
UK goat meat or dairy products. The committee was presented
with experimental evidence about the case.
SEAC agreed that the evidence suggested the goat had indeed
been infected with BSE. However, it was noted that the goat had
been born around the time of the peak of the BSE epidemic and
before the feed bans had been introduced. Therefore, it was likely
to have been exposed to feed highly contaminated with the BSE
agent. It was noted that BSE had not been found in the offspring
of this goat or in other goats from the farm. It therefore appeared
to be an isolated case.
SEAC concluded that there is no evidence for BSE in the current
UK goat herd, and as goats are no longer exposed to
contaminated feed the likelihood of goats in the current flock being
infected with BSE is low. However, SEAC noted that surveillance
of TSEs in goats is very limited and welcomed plans to increase
surveillance and to examine other historical samples of goats that
may be available, which should enhance confidence in this
The committee concluded that, on the basis of current evidence,
and the control measures currently in place aimed at reducing
potential risk, it is reasonable for the FSA to continue not to advise
against the consumption of goat meat or diary products. However,
as surveillance is very limited, and the distribution of BSE
infectivity in goats is not well understood, a potential risk of BSE
from goat meat and dairy products cannot be entirely excluded.
A recent paper (Heikenwalder et al., published 2005 in Science)
reported that in mouse models, chronic inflammation altered the
tissue distribution of scrapie prions and infectivity. In these mice,
scrapie prions and infectivity had been detected in tissues not
normally infective. The FSA asked SEAC to consider the
implications of the findings for specified risk material (SRM)
controls which prevent animal tissues known to be potentially
infective reaching the human food chain.
The committee agreed the findings were very interesting. It was
noted that the immune system of the mice had been genetically
modified resulting in very specific and severe forms of
inflammation which may not reflect conditions that normally apply
on the farm. Thus, it would be premature to conclude that such
inflammation altered the effectiveness of SRM controls. Further
work would be required to investigate more fully the influence of
inflammation on prion disease and infectivity.
The committee noted that inspections of animals at abattoirs
restricted the entry of unhealthy animals into the food chain. Thus,
animals with severe inflammation should normally be excluded
from the food chain. Nevertheless, the committee agreed that to
minimise potential risk the Meat Hygiene Service should continue
to be particularly vigilant in this area.


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