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From: TSS (216-119-143-165.ipset23.wt.net)
Subject: Board meeting agenda: 9 December 2004 Tuesday, 07 December 2004 FSA (BSE goat/sheep update and more)
Date: December 7, 2004 at 9:02 am PST
-------- Original Message --------
Subject: Board meeting agenda: 9 December 2004 Tuesday, 07 December 2004 FSA
Date: Tue, 7 Dec 2004 09:15:28 -0600
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy
To: BSE-L@LISTSERV.KALIV.UNI-KARLSRUHE.DE
##################### Bovine Spongiform Encephalopathy #####################
1
FSA 04/12/04 AGENDA ITEM 6, 9 DECEMBER 2004
BSE AND SHEEP CONTINGENCY POLICY
Executive summary
1. This report considers the approach the Agency would take to a finding
of BSE in
UK sheep or goats, with present knowledge. A number of possible risk
management options are explored ranging from the current FSA policy of
allowing only resistant and semi-resistant sheep under 12 months into
the food
chain, removing all sheep above a certain age, extending the list of
specified risk
material and introducing testing in abattoirs. Provisional costs and an
indication of
risk reduction are presented for these risk management options.
2. The Board is invited to agree:
· That it remains the FSAs policy, in the event of a finding of BSE in
UK sheep,
and with current SRM controls continuing to apply, and subject to any
overarching EU measures being introduced, to recommend that only resistant
and semi-resistant sheep under 12 months could enter the food chain.
· That in the event of a finding of BSE in a UK goat, we would follow the
approach being taken at EU level in relation to a possible finding of
BSE in a
French goat.
· That a stakeholder process be initiated with the aim of seeking views
on the
current contingency plans and other alternatives, in relation to sheep and
goats.
· That the outcome of the consultation process be fed back to the Board with
the aim of completing the current contingency planning policy review by
autumn 2005.
TSE Division
Contacts: Alan Harvey Tel: 020 7276 8303 (GTN 7276 8303)
Email: alan.harvey@foodstandards.gsi.gov.uk
Paul Holley Tel: 020 7276 8306 (GTN 7276 8306)
Email: paul.holley@foodstandards.gsi.gov.uk
Irene Hill Tel: 020 7276 8324 (GTN 7276 8324)
Email: irene.hill@foodstandards.gsi.gov.uk
2
FSA 04/12/04 AGENDA ITEM 6, 9 DECEMBER 2004
BSE AND SHEEP CONTINGENCY POLICY
Issue
1. To consider the current FSA policy on action necessary in the event
of a finding
of BSE in sheep in the UK flock.
Strategic aim
2. Links to the Agencys aims to ensure BSE controls are based on latest
scientific
knowledge and are effectively enforced
Background
Scrapie and BSE in sheep and goats
3. Scrapie is one of a group of diseases known as transmissible spongiform
encephalopathies (TSEs) which also includes BSE and CJD. Scrapie is known to
have been present in UK sheep for at least 250 years and is not
considered to be
a risk to human health.
4. BSE was spread to many cattle through the practice of including meat
and bone
meal (MBM), prepared from rendered carcasses, in cattle feed. The expert
view
is that the consumption of BSE infected meat or meat products is the
cause of
vCJD from which 146 people have died to date in the UK.
5. The same MBM was included in sheep and goat feed and therefore there
is a risk
that some UK sheep and goats may have been infected with BSE. We do not
know if BSE has got into the UK sheep or goat populations, but if so,
only a small
number of sheep and goats could be affected (see paragraph 23).
6. No cases of BSE in sheep or goats have been found to date in the UK.
However
the European Commission have reported a possible case of BSE in a French
goat slaughtered in October 2002 (see paragraphs 19 and 20). Sheep and goats
have been experimentally infected with BSE, which has demonstrated
similarities
between scrapie and BSE, including that the two diseases cannot be
distinguished by their symptoms. Therefore a differential diagnosis of
scrapie or
BSE has to rely on laboratory tests.
3
7. The risk to consumers from any cattle infected with BSE is reduced to
very low
levels, in particular through the removal and destruction of specified
risk material
(SRM). SRM includes all those tissues that have been shown by experimental
analysis to carry BSE infectivity in cattle. Because these tissues are
limited, it is
practical for them to be removed whilst still leaving the main carcass
available for
consumption. It has been estimated that in cattle over 99% of
infectivity in an
infected animal will be removed as SRM.
8. By contrast, in experimentally infected sheep, BSE infectivity is
found in many
different tissues as the disease progresses. SRM are currently removed from
sheep and goats as a precautionary measure against the possibility of
BSE being
present. However it would not be proportionate to remove all potentially
infected
tissues as a precautionary measure. Under the current controls it has been
estimated that the infectivity that could enter the food chain from a
single sheep
of the most susceptible genotype with clinical BSE, could be over a thousand
times that from a cow with clinical BSE. The FSA has concluded that
should BSE
be found in the sheep flock, additional measures beyond the current SRM
controls would be necessary.
June 2002 Board Conclusions
9. In 2002, a core stakeholder group, together with scientific experts,
discussed the
action that would need to be taken if BSE were found in the UK flock. The
current policy is based on the situation in 2002 as defined in paper FSA
02/06/02.
This essentially restricts sheep and goat meat and dairy products
entering the
food chain to those from animals with a genetic resistance to TSEs. For
sheep
this has been interpreted as meaning fully resistant animals of any age
and semiresistant
animals under 12 months. To date no resistant genotype has been
found in goats and therefore all goat meat and milk would need to be
kept out of
the food chain under this policy. It was also recognised that, at that
time, almost
no UK sheep could reliably be identified as being of the appropriate
genotype.
Testing for scrapie and BSE
10. Currently, under EU legislation, all sheep or goats that are
suspected of having
scrapie must be reported and their brains tested to see if they have a
TSE. In
addition a minimum number of animals must be tested to provide data on
scrapie
4
prevalence. A positive test result demonstrates that the animal is
suffering from a
TSE. However the basic tests used do not distinguish between scrapie and
BSE.
11. A number of laboratories have now developed rapid tests that are
capable of
distinguishing between the BSE samples obtained from experimentally infected
sheep and known scrapie samples. One of these has been applied to all
available TSE positive GB sheep samples from 1998 onwards, and is applied to
all new positive samples. BSE has never been demonstrated in the UK sheep
flock, but the results of this testing have been used to estimate the
possible
hypothetical maximum level (see paragraph 23). More detail on testing is
given in
Annex A.
12. At their meeting in September SEAC acknowledged that the testing to
distinguish
BSE from scrapie is becoming more robust. However there is still some
uncertainty surrounding these tests as none has been shown beyond all
doubt to
differentiate BSE from scrapie, but work is on going.
13. Increasing the testing of sheep and goats is one possible risk
management
option that is considered below (see paragraph 30).
Genotyping and the NSP
14. For a number of years it has been clearly recognised that sheep vary
in their
susceptibility to scrapie. In the UK, the National Scrapie Plan (NSP and
NISP in
NI) developed by rural affairs Departments has been working towards an
increase in the level of the resistant genotypes in the national flock
whilst
decreasing the level of those most susceptible to scrapie. To date over
1 million
sheep have been genotyped, mainly in the flocks at the top of the breeding
pyramid. The ultimate objective is to eliminate TSEs from the flock,
which would
benefit both animal health and protect the consumer, should BSE be in sheep.
Defra are working to reduce scrapie incidence by 40% by 2010, but total
elimination may take 20 years or more. A voluntary scheme has been in place
for over 4 years but will be replaced with a compulsory EU scheme from 1
April
2005.
15. Restricting sheep that may enter the food supply based on their
genotype and
age is one possible risk management option that is considered below (see
paragraph 27). Further details on genotyping are given in Annex B.
5
SRM controls
16. In the UK SRM controls have been applied to sheep and goats as a
precaution
against the possibility that they may be infected with BSE since 1996.
However,
as noted in paragraph 8, these do not remove all the tissues that have been
shown to carry infectivity. One risk management option that is
considered (see
paragraph 29 below) is to increase the number of tissues that are
included as
SRM and/or the age at which the controls are applied.
EU Position
EU law
17. TSEs are not exclusively a UK problem. Scrapie is endemic in many EU
countries and, with the exception of Sweden and 4 accession states, all
member
states have experienced at least one case of BSE in cattle. The EC has
enacted
legislation directly applicable in all member states (EC999/2001 and
amendments) to regulate the handling and surveillance of cattle, sheep
and goats
with regard to BSE and scrapie. However this does not yet include any
action to
be taken outside the source farm, in the event of a possible finding of
BSE in
sheep or goats. A first phase, which is currently under negotiation,
will cover the
process to be followed to identify a case of BSE. Any TSE sample from a
sheep
or goat, in any member state, that has any similarities to BSE will be
subjected to
all the tests in the ring trial (see Annex A), with an expert panel
organised by the
Community Reference Laboratory meeting to agree the result.
18. The action to be taken following a result that is determined to be
BSE-like has
not yet been agreed. Commission officials in bilateral discussions have
indicated
their concern about any member state taking unilateral action either for
a sheep
or goat with BSE in their country, or against another member state with
such a
case. The FSA legal view is that unilateral action under the EU safeguard
procedures could only be taken if there were considered to be an
immediate risk
not contemplated by the current rules.
French goat with possible BSE
19. The EC have recently reported that a French goat slaughtered in 2002
might
have BSE. An expert group considered the results of a number of tests
that have
been carried out on samples from this animal. On November 26 2004 the
6
Commission reported that further work was necessary before the group could
come to a conclusion as to whether the test results were indicative of
BSE. This
work is expected to take approximately two months. Some 140,000 goats have
been TSE tested since April 2002 in the EU with 111 found positive for TSE
infection by screening test. No other goats have been reported as
possibly having
BSE.
20. An Opinion from the European Food Safety Authority (EFSA) in
November 2004
has concluded that, while there is a paucity of experimental data, the
milk and
cheese from goats are unlikely to pose a TSE risk if taken from an
animal without
clinical BSE infection. In the meantime member states will be meeting
with the
Commission to consider possible risk management options should this goat
eventually be confirmed as probable BSE. The FSA is consulting stakeholders
on this point.
Contingency planning
21. Defra have published an overarching contingency plan covering the
action that
would need to be taken in the UK if BSE was found in sheep. It is based
on the
current FSA policy of allowing only known genetically resistant or
semi-resistant
sheep with an age cut -off into the food supply. The EU requires that each
member state draw up such a plan based on similar worst case planning
assumptions. This advice is likely to be considered further by EFSA perhaps
leading to an EU contingency plan being drawn up. It is stressed in the
opening
section of the Defra plan that it is a living document which will be
subject to
changes in the light of developments and emerging science.
Developments Since 2002
Estimate of possible BSE prevalence
22. VLA have now applied their molecular test to differentiate BSE from
scrapie to a
total of 2147 samples from sheep TSE cases which have come from 450
different
flocks. None has given a BSE-like result. This work was presented to SEAC in
September 20043 who cautioned that the absence of a BSE-like result
cannot be
considered to be the final word. This is because of the limitations on
the test
3 See attached SEAC notes at Annex D
7
methodology and the relatively small number of samples.
23. These results if taken to demonstrate an absence of BSE - can be
used to
estimate the maximum proportion of sheep TSE cases that could be BSE. Based
on SEAC recommendations the estimate is based on the number of flocks, not
the number of sheep where a TSE case has tested negative for BSE. The
resulting estimate is that the proportion of TSE cases that could
possibly be BSE
is in the range 0 - 0.66% (95% confidence interval). With over 77,000
flocks in
GB in 2003 a maximum estimate of 0.66% translates into some 4 to 5
flocks with
possible BSE cases. From this it can also be estimated that if BSE were
in the
GB sheep flock the maximum number of sheep that might be infected with BSE
(as distinct from BSE cases), would be over 700 in a flock of some 33
million
sheep and lambs. In 2002 an estimate of a range of between 0 and 2% for the
proportion of sheep TSE cases that could be BSE was obtained, based on the
negative results for the mouse bioassay of approximately 200 TSE positive
samples.
24. Modelling work, based on these 2004 calculations, has been carried
out by Dr.
Angela McLeans team at Oxford to estimate the effect of a number of
potential
risk management measures. The results are summarised in Annex C. There are
limited data to underpin this study. However SEAC3 noted that the
estimate of
infectivity entering the food chain from a sheep with clinical BSE
suggested this
could present a significantly greater risk than a cow with clinical
BSE. They also
agreed that, although there was no evidence of a large, self-sustaining
epidemic
of BSE in sheep, the model suggests that the presence of small epidemics
in a
few flocks cannot yet be ruled out. A summary of SEAC deliberations on this
subject is at Annex D.
25. As part the contingency planning exercise the FSAs Economics team have
calculated the financial costs of implementing various risk management
options
based on Defra cost estimates. These are also given in Annex C.
Options
26. As can be seen from Annex C, the possibilities for action in the
event of a finding
of BSE in sheep include allowing only resistant and semi-resistant
animals under
8
12 months into the foodchain, removing all sheep above a certain age,
extending
the list of SRM and introducing testing at abattoirs.
27. The most effective risk management option in terms of risk reduction
is to allow
only resistant and semi-resistant sheep into the foodchain, in line with
the current
FSA policy endorsed by the Board in 2002 and the EU guidelines for
contingency
planning.
28. Unlike cattle, sheep do not have a universal tracking system in
place, such as ear
tagging and passports, which would allow for individual identification.
However a
flock register scheme is due to be introduced in 2005 . In addition,
there is an
EU plan for the introduction of compulsory electronic identification
from 2008 for
all sheep over 12 months of age but this is some way off, and in any
case will not
apply to the majority of sheep entering the food chain which are under
12 months
of age.
29. Additional across-the-board SRM controls are a possibility but the
practical
difficulties of removing all lymph nodes, which are distributed through
out the
carcase, would be considerable. Extension of the SRM controls to other
tissues
arguably would not add sufficiently to the risk benefit to be
worthwhile, except
perhaps if intestine were to be singled out.
30. Testing animals over 12 months would also not appear to reduce risk
sufficiently
and would be dependent on the acceptability of the current screening
tests, which
have yet to be fully validated for sheep and goats.
31. The most straightforward practical step, though draconian in its
immediate
implications, remains that of stopping UK sheep from entry into the food
chain
unless demonstrably of the resistant or semi-resistant genotype. In the
event of a
BSE finding, and based on earlier FSA advice, Defra currently envisage
that in a
worst case scenario the entire lamb crop for one breeding season could
be lost.
Only fully resistant rams would then be used in breeding to confer semi
resistant
status on the lambs that would be produced in the following years crop.
A whole
raft of enforcement issues would then arise, associated with implementing a
workable manifestation of this policy, which we understand Defra are
currently
scoping.
9
32. In the future, should a larger sample of animals on testing be found
negative for
BSE, the Agency could then determine that prevalence and risk was low enough
at that time for voluntary options to be considered. These could include
advising
that there is now a demonstrable small risk of BSE associated with
eating sheep
meat, such that consumers could, in effect, decide for themselves
33. The Agencys approach needs to be proportionate as knowledge in this
area
develops. Although there are increasing numbers of TSE positive sheep
testing
negative for BSE, there is still the possibility of a small number of
BSE infected
sheep flocks where the infectious load entering the food chain from just one
clinical BSE infected sheep, as mentioned earlier, would be over a thousand
times that of a similar cow.
34. In order to seek wider views, it is proposed that a stakeholder
process be
initiated. The aim would be to seek their views on the current FSA
contingency
planning policy and strategies given in Annex C, as well as possible
combinations
of options generated by the modelling work on potential risk management
measures (see paragraph 24). Stakeholder views on the possible interventions
and their proportionality would inform the Agencys assessment of future
risk
management options which would be reported back to the Board in 2005. In the
meantime it is recommended that the Agencys contingency policy remain based
on genotype and age cut-off.
35 The Board is invited to agree:
· That it remains the FSAs policy, in the event of a finding of BSE in UK
sheep, and with current SRM controls continuing to apply, and subject to any
overarching EU measures being introduced, to recommend that only resistant
and semi-resistant sheep under 12 months could enter the food chain.
· That in the event of a finding of BSE in a UK goat, we would follow the
approach being taken at EU level in relation to a possible finding of
BSE in a
French goat.
· That a stakeholder process be initiated with the aim of seeking views
on the
current contingency plans and other alternatives, in relation to sheep and
goats.
· That the outcome of the consultation process be fed back to the Board with
the aim of completing the current contingency planning policy review by
Autumn 2005.
10
ANNEX A
TSE Testing Of Sheep And Goats
1. Under EU law all sheep or goats that are suspected of having scrapie
must be
reported. These are required to be slaughtered and their brains tested
to see if
they have a TSE. In addition a minimum number of animals over 18 months of
age must be tested to provide data on scrapie prevalence. In the UK the
required
sample size has varied, but is currently set at 10,000 sheep slaughtered for
human consumption and 10,000 sheep and 500 goats that are fallen stock
(found
dead on farm) per annum. The results for 2003 and 2004 to date are shown in
the Table below.
2. A positive test result demonstrates that the animal is suffering from
a TSE as the
basic tests used do not distinguish between scrapie and BSE.
Testing for BSE
3. A number of laboratories have now developed rapid tests that are
capable of
distinguishing between the BSE samples obtained from experimentally infected
sheep and known scrapie samples. The BSE samples include sheep that have
been infected directly from cattle brain, and those that have been
secondarily
infected with brain from these first sheep. This is an experimental model
simulating the fact that if BSE were to be found in the flock now, it
would have to
have been passed on (in the same way that scrapie is passed on) to the sheep
alive today from those that ate the contaminated MBM before 1996, when a
reinforced feed ban was introduced.
4. In the UK two different tests which distinguish between BSE and
scrapie have
been developed by staff at the Veterinary Laboratories Agency (VLA). One of
these has been applied to all available TSE positive GB sheep samples from
1998 onwards, and is applied to all new positive samples. The results of
this
testing have been used to calculate the possible maximum level of BSE in
the GB
flock. (see paragraph 23 in the main text) In Northern Ireland
differential testing
for BSE and scrapie has been carried out on all TSE positive samples since
2001.
Ring trial
5. As well as the UK developed tests there have also been three similar
molecular
tests developed in France. These five tests have been evaluated in a
ring trial
process where designated laboratories all test the same samples and
compare
11
their results thus providing assurance on their reliability. All of the
tests were
found to correctly identify the same scrapie and BSE samples. Work is in
progress to include a further test, which is based on a different
principle (the
conformation-dependent immunoassay, developed in the US). The
Governments TSE advisory committee (SEAC) have recently stressed the
importance of the inclusion of this further test in the ring trial as it
does not rely on
a process common to the other tests.
Atypical scrapie
6. As previously reported (April 2004) the UK recently identified two
sheep samples
that initially showed BSE-like properties. The conclusion was that,
whilst these
were not typical of normal scrapie, neither did they resemble BSE in
sheep, at
least as the profile is understood from experimental work.
Anomalous test results
7. Another testing anomaly that has been reported by several member states,
including the UK, are the samples that are positive by the rapid test
used for
surveillance, but which were initially negative by the further tests
used to confirm
the result. Further testing has shown that these animals do have some
form of
abnormal prion1 in their brains and are therefore now confirmed
positive. Active
research into these samples is continuing.
Mouse bioassay
8. Prior to the development of molecular test methods BSE could only be
differentiated from scrapie by inoculating the material into mice and
looking at the
pattern of disease in their brains and the susceptibility of specific
mouse strains.
This is still regarded as a robust method for identifying BSE. However this
process takes several years. Genetically altered mice that come down with
disease more rapidly are now available, but testing still takes many
months. Work
is underway in preparation for putting the atypical samples (paragraph 6
above)
into mouse bioassay.
1 The prion is the protein in the brain that is changed when an animal
is suffering from a TSE
12
Results for scrapie testing the UK for 2003 and 2004
Tested in
2003
Confirmed
Positive
Tested in
2004
Confirmed
Positive
Scrapie
suspects -
sheep
553 440 3,789a 239
Abattoir survey
- sheep 72,518 46 10,278 6
Fallen stock
survey - sheep 5,126 13 4,432 5
Abattoir survey
- goats 191 1 12b 0
Fallen stock
survey - goats 54 0 42 0
a In 2004 this total includes the additional animals culled and tested
under the voluntary scrapie
affected flocks scheme.
b Currently not a legal requirement
13
ANNEX B
Genotyping and the NSP
Genetic resistance to TSEs
1. For a number of years it has been clearly recognised that sheep vary
in their
susceptibility to scrapie. It is now known that the most resistant
genotype may not
be fully resistant to all types of TSE. To date 3 of 19 experimental
animals of the
most resistant type have come down with BSE when it was injected into their
brains, but none of 8 fed BSE have shown any signs of disease. In addition
some of the anomalous sheep (Annex A, paragraph 7) are of this genotype.
The NSP
2. In the UK the National Scrapie Plan (NSP and NISP in NI) developed by
rural
affairs Departments has been working towards an increase in the level of the
resistant genotypes in the national flock, whilst decreasing the level
of those most
susceptible to scrapie. Given the results above, the validity of
selecting for the
resistant genotypes, has been considered by the EFSA experts. They concluded
that increasing genetic resistance may decrease the incidence of clinical
disease. However it is possible that a carrier state may exist in
these sheep2. To
date over 1 million sheep have been genotyped, mainly in the flocks at
the top of
the breeding pyramid. The ultimate objective is to eliminate TSEs from
the flock,
which would benefit both animal health, and protect the consumer should
BSE be
in sheep. Defra are working to reduce scrapie incidence by 40% by 2010, but
total elimination may take 20 years or more. The effect on BSE, should it be
present, will depend on the uptake and the rate at which the most BSE
susceptible genotype can be decreased. A voluntary scheme has been in place
for over 4 years but will be replaced with a compulsory EU scheme from 1
April
2005.
3. The genotyping program has progressed such that some 30% of genotyped
rams
are now of the resistant genotype, which can be used to sire lambs that
are at
least semi-resistant (currently estimated to be 74% of lambs entering
the food
chain). But if BSE were found in sheep these would not be eligible to
enter the
food chain under current FSA advice unless they could be positively
identified,
either on an individual basis (as for cattle) or as belonging to a
particular flock.
2 The EFSA Journal, 2003
14
4. A voluntary flock register scheme to recognise their TSE resistance
has been
proposed by the EU. This will recognise flocks where rams (and possibly
ewes)
have been genotyped under the NSP, and is due to be launched in 2005.
Compulsory Scrapie flocks scheme
5. EU legislation has recently introduced the requirement to cull or
genotype herds
confirmed to have scrapie so as to retain the most resistant genotypes.
However
this can only be applied for known scrapie cases and where the flock can be
identified.
ANNEX C
STRATEGIES EST.
AVERAGE
ANNUAL
COST
£
RISK REDUCTION PRACTICALITIES
1. To allow into the food chain:
· resistant sheep of all ages
· semi resistant sheep of under 12 months
· Current SRM applies
£480m Very High This is the FSAs stated favoured policy from 2002. The
problem here is one of having a reliable system in place
which could readily identify the sheep. There is no such
universal system yet in place, such as ear tagging and
passports for individual animals, as with cattle. In the
absence of that, there would be no alternative but to
stop all sheep from entering the food chain, if this
option were followed.
2. Remove all sheep over 12 months
· Current SRM applies
£90m
(ewes only)
Low More straightforward (though ageing a sheep can only
ever be approximate).
3. Remove more SRM
· Current SRM applied to all animals
· Max. option add intestine, lymph nodes,
liver, stomach and thymus to SRM
£20m -
£60m
High Practical difficulties of removing lymph nodes would be
considerable. However the intestine, which is practical
to remove, is the biggest contributor. Would require
increase in time and resources at cutting premises.
4. Test all sheep over 12 months
· -ve allowed into food chain
£100m
(cull ewes)
Low More straightforward (though ageing a sheep can only
ever be approximate).
Would require considerable adjustment and add major
burden to those abattoir handling older sheep.
Notes: Costs are provisional estimates only.
Risk reduction categories: Very High: 100-91%, High: 90 76%, Medium 75
41%, Low below 40%
Costs for Options 1, 2 & 4 are equivalent annual economic costs. The
cost for option 3 is an annual cost.
16
Dairy products
Unlike cattle, in sheep the lymph nodes of susceptible sheep carry BSE
infectivity and lymphocytes are found in milk.
However some experiments injecting milk from infected sheep/goats into
mice have been done and not shown infectivity, but
the data are limited. Given this uncertainty, sheep and goat milk and
dairy products are included in the current FSA advice
on a precautionary basis.
They are not included in the table above, but in 2002 the value of this
industry was estimated to be over £16 million.
However, the full economic impact will be limited as the cheese industry
is likely to be able to find alternative inputs or import
supplies to continue production. Furthermore, substitute products will
gain (such as cows milk and soya milk as well as
imports), thus producing an offsetting benefit.
SRM controls
The following tissues are currently designated as SRM for sheep and
goats and must be removed and destroyed:
The skull, including brain, eyes and tonsils, and the spinal cord of
animals over 12 months;
The spleen and ileum of animals of all ages.
These requirements apply to all member states and to all imports into
the EU from other countries (with the exception of
sheep or goats born, reared and slaughtered in 17 countries considered
free of BSE). 18
ANNEX D
Summary of SEAC discussion on BSE & sheep: the FSA contingency policy
The Spongiform Encephalopathy Advisory Committee (SEAC) was provided with
background information on the analytical techniques used to detect and
discriminate BSE and scrapie in sheep samples, and the preliminary
results from
an on-going ring-trial comparing the analytical methods used by different
research groups.
SEAC was also presented with the findings from two studies modelling the:
· maximum number of sheep that could potentially be infected with BSE in
the GB
sheep flock based on testing results from retrospective and prospective
surveillance of TSEs in sheep (Simon Gubbins; VLA);
· Potential BSE infectivity in sheep together with strategies to reduce
the risk of
BSE infectivity entering the food chain based on a) the relative
susceptibilities of
sheep genotypes to BSE infection, b) removal of specified risk materials
or c)
TSE testing (Angela McClean, Oxford).
TSE test methods
SEAC noted that the analytical methods used to detect TSEs in sheep, and
distinguish BSE from scrapie, were becoming more robust. A combination
of tests
now provides a reasonably rigorous, although not completely unambiguous,
approach to distinguishing conventional scrapie from conventional BSE in
sheep.
The results from the on-going ring-trial will be important to assess
more fully the
robustness of the methods. It was considered important to analyse final
data from
the conformation-dependent immunoassay (CDI) method in the ring-trial
because,
unlike all the other methods used, it does not rely on differential
enzyme (Proteinase
K) digestion of the prion protein (PrP). Thus, it could be an important
and possibly
powerful additional discriminatory test.
SEAC considered that, using the currently available tests, the vast
majority of the
TSE's detected in sheep in prospective and retrospective surveys were
likely to be
scrapie and not BSE. Furthermore, no unambiguous case of BSE in sheep
has yet
19
been detected. Nevertheless, because of limitations in methodology and
the number
of samples tested this conclusion cannot be considered certain.
SEAC noted that two surveillance samples had given atypical test results
that were
inconsistent with the criteria used to define either BSE in sheep or
scrapie infection.
It was considered possible that these two atypical TSE test results
could indicate the
presence of a variant form of scrapie, a variant form of BSE, another as yet
uncharacterised TSE, or reflect a modifying effect of a particular sheep
genotype. It
was noted that tests of orally transmitted and passaged BSE in all sheep
genotypes
had not yet been conducted. The committee agreed it was very important
to conduct
more research to try to establish the nature of these samples and
particular urgency
should be given to in vivo infectivity studies.
Possible prevalence of BSE in sheep
SEAC generally accepted the approach used to model the possible
prevalence of
BSE in sheep. However, it was noted that the model depended on the
ability of the
tests used to effectively detect and discriminate between scrapie and
BSE and
current tests were not yet 100% reliable (see above).
Perhaps more significantly, SEAC considered that, because many of the
samples
included in the surveillance had come from farms with a large number of
scrapie
cases, which may be more likely to report scrapie cases, the data may
have been
influenced by a selective ascertainment bias. It was agreed that basing the
calculation of the prevalence of BSE in sheep on TSE affected flocks,
rather TSE
cases, was preferable. Nevertheless, even if only flocks are considered,
the effect of
non-random sampling may have led to an underestimation of the number of
potential
BSE cases. It was suggested that that if the modelling was restricted to
the results
obtained from active surveillance the bias could be minimised, although
such an
analysis would significantly reduce the data that could be included in
the model.
Additionally, it was suggested that data from a 2002 scrapie postal
survey, relating to
the distribution of cases on scrapie affected farms, could be compared
with the
passive surveillance data in order to assess the possible effect of the
sample bias.
Impact of risk reduction strategies
SEAC generally accepted the modelling approach used and acknowledged that it
was extremely difficult to estimate the potential BSE infectivity
entering the food
20
chain from tissues of infected sheep. The committee noted that the model
of BSE
infectivity in sheep was based on a large number of assumptions. For
example, the
model assumed that the pathogenesis of BSE and scrapie in sheep may be
similar,
yet this is still largely unknown. In addition, although ARR homozygous
sheep
appear to be the most resistant PrP genotype, sheep of this genotype
could not now
be considered to be completely resistant to TSE infection. SEAC noted
that, in
contrast to the assumptions made in the modelling, sheep breeds were
heterogeneous and methods of husbandry differed considerably between farms.
Also, it may not be appropriate to generalise about the prevalence and
distribution of
PrP genotypes in sheep because PrP genotype can extremely variable between
different sheep breeds.
It was noted that estimates used for the quantity of sheep tissues
entering the food
chain differed from values used by other research groups. In addition,
the effective
removal of lymph nodes was considered unrealistic.
Bearing in mind these assumptions and caveats, SEAC noted that:
· the model of BSE infectivity in sheep tissues suggested that a single BSE
infected sheep entering the food chain could present a significantly
greater risk to
public health compared with the current risk associated from a single
infected
cow;
· although there was no evidence of a large self-sustaining epidemic of
BSE in
sheep, the model suggests that the presence of small epidemics in a few
flocks
cannot yet be ruled out;
· the models suggest that strategies based on control of specified risk
material or
TSE testing are currently unlikely to be very effective in minimising
risk of human
infection. The committee considered that should the sensitivity of TSE
tests be
improved they may be effective in the future.
· the model suggests that strategies based on the PrP genotype of sheep
would be
the most effective in reducing risk of human infection. However, the
committee
stressed that the magnitude of the relative reductions in risk between
the various
strategies modelled could not be regarded as absolute.
SEAC Secretariat 11 October 2004 http://www.food.gov.uk/multimedia/pdfs/fsa041204.pdf FSA 04/12/02 AGENDA ITEM 4, 9 DECEMBER 2004
WALL REVIEW OF CASUALTY TESTING FAILURES: NEXT STEPS
Executive Summary
1. This paper asks the FSA Board to note the action taken and agree the
action
planned to address the recommendations made in the report of the independent
inquiry into BSE-testing failures by the MHS in Great Britain (the Wall
Report).
2. The inquiry into the failure by the MHS to test an estimated 229
casualty cattle
aged between 24-30 months for BSE, was initiated by the FSA Board in June
2004 following MHS internal audits and management checks that uncovered
these failures. The inquiry was set up to find out the reasons for the
failings by
the MHS and why they were not identified earlier; as well as to make
recommendations to improve the robustness of the testing arrangements so
as to
minimise the likelihood of this, or a similar problem, recurring.
3. The FSA Board is asked to:
· agree the action plan (Annex D) to address the 13 recommendations made in
the report;
· note the action already taken; and
· note that progress reports on implementation of the action-plan will be
considered at future MHS Board meetings and included in future reports to
the FSA Board by the Chairman of the MHS Board.
Meat Hygiene & Veterinary Division
Contacts: Peter Hewson Tel 020 7276 8344
Email: peter.hewson@foodstandards.gsi.gov.uk
David Hart Tel 020 7276 8343
Email: david.hart@foodstandards.gsi.uk FULL TEXT 73 PAGES ; http://www.food.gov.uk/multimedia/pdfs/fsa041202.pdf Board meeting agenda: 9 December 2004 Tuesday, 07 December 2004 http://www.food.gov.uk/aboutus/ourboard/boardmeetings/boardmeetbranch2004/boardmeeting091204/boardagenda091204 NOW, back to 1976 ; 12/10/76
AGRICULTURAL RESEARCH COUNCIL
REPORT OF THE ADVISORY COMMITTE ON SCRAPIE
Office Note
CHAIRMAN: PROFESSOR PETER WILDY snip... A The Present Position with respect to Scrapie
A] The Problem Scrapie is a natural disease of sheep and goats. It is a slow
and inexorably progressive degenerative disorder of the nervous system
and it ia fatal. It is enzootic in the United Kingdom but not in all
countries. The field problem has been reviewed by a MAFF working group
(ARC 35/77). It is difficult to assess the incidence in Britain for
a variety of reasons but the disease causes serious financial loss;
it is estimated that it cost Swaledale breeders alone $l.7 M during
the five years 1971-1975. A further inestimable loss arises from the
closure of certain export markets, in particular those of the United
States, to British sheep. It is clear that scrapie in sheep is important commercially and
for that reason alone effective measures to control it should be
devised as quickly as possible. Recently the question has again been brought up as to whether
scrapie is transmissible to man. This has followed reports that the
disease has been transmitted to primates. One particularly lurid
speculation (Gajdusek 1977) conjectures that the agents of scrapie,
kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of
mink are varieties of a single "virus". The U.S. Department of
Agriculture concluded that it could "no longer justify or permit
scrapie-blood line and scrapie-exposed sheep and goats to be processed
for human or animal food at slaughter or rendering plants" (ARC 84/77)"
The problem is emphasised by the finding that some strains of scrapie
produce lesions identical to the once which characterise the human
dementias" Whether true or not. the hypothesis that these agents might be
transmissible to man raises two considerations. First, the safety
of laboratory personnel requires prompt attention. Second, action
such as the "scorched meat" policy of USDA makes the solution of the
acrapie problem urgent if the sheep industry is not to suffer
grievously. snip... 76/10.12/4.6 http://www.bseinquiry.gov.uk/files/yb/1976/10/12004001.pdf http://www.bseinquiry.gov.uk/files/yb/1976/10/12002001.pdf CJD CASE 1977 ? (notes) http://www.bseinquiry.gov.uk/files/yb/1977/00/00002001.pdf
CJD YOUNG PEOPLE
in the USA, a 16 year old in 1978;
ALSO IN USA;
(20 year old died from sCJD in USA in 1980 and a 16 year
old in 1981. see second url below) in France, a 19 year old in 1982; in Canada, a 14 year old of UK origin in 1988; in Poland, cases in people aged 19, 23, and 27 were identified in
a retrospective study (published 1991), having been originally
misdiagnosed with a viral encephalitis;
Creutzfeldt's first patient in 1923 was aged 23.
ALSO;
http://www.bseinquiry.gov.uk/files/yb/1995/10/27013001.pdf
20 year old died from sCJD in USA in 1980 and a 16 year
old in 1981. A 19 year old died from sCJD in
France in 1985. There is no evidence of an iatrogenic
cause for those cases....
http://www.bseinquiry.gov.uk/files/yb/1995/10/20006001.pdf
1: J Infect Dis 1980 Aug;142(2):205-8
Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to
nonhuman primates.
Gibbs CJ Jr, Amyx HL, Bacote A, Masters CL, Gajdusek DC. Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of
sheep and goats were transmitted to squirrel monkeys (Saimiri
sciureus) that were exposed to the infectious agents only by their
nonforced consumption of known infectious tissues. The asymptomatic
incubation period in the one monkey exposed to the virus of kuru was
36 months; that in the two monkeys exposed to the virus of
Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and
that in the two monkeys exposed to the virus of scrapie was 25 and
32 months, respectively. Careful physical examination of the buccal
cavities of all of the monkeys failed to reveal signs or oral
lesions. One additional monkey similarly exposed to kuru has
remained asymptomatic during the 39 months that it has been under
observation. PMID: 6997404 http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6997404&dopt=Abstract Adaptation of the bovine spongiform encephalopathy agent to primates
and comparison with Creutzfeldt- Jakob disease: Implications for
human health THE findings from Corinne Ida Lasmézas*, [dagger] , Jean-Guy Fournier*,
Virginie Nouvel*, Hermann Boe*, Domíníque Marcé*, François Lamoury*, Nicolas Kopp [Dagger ] , Jean-Jacques Hauw§, James Ironside¶, Moira Bruce [||] , Dominique Dormont*, and Jean-Philippe Deslys* et al, that The agent responsible
for French iatrogenic growth hormone-linked CJD taken as a control is
very different from vCJD but is similar to that found in one case of
sporadic CJD and one sheep scrapie isolate; http://www.pnas.org/cgi/content/full/041490898v1 NOW, back to 2004 USA ; Infected and Source Flocks As of September 30, 2004, there were 67 scrapie infected and source
flocks (figure 3
).
There were a total of 100** new infected and source flocks reported for
FY 2004 (figure 4
).
The total infected and source flocks that have been released in FY 2004
are 77 (figure 5
).
The percent of new infected and source flocks cleaned up or on clean up
plans was 96%. In addition, as of September 30, 2004, 368 scrapie cases
have been confirmed and reported by the National Veterinary Services
Laboratories (NVSL) in FY 2004, of which 54 were RSSS cases (figure 6
,
and figure 7
).
Thirteen cases of scrapie in goats have been reported since 1990 (figure
8
).
One new goat case was reported in FY 2004. New infected flocks, source
flocks, and flocks released for FY 2004 are depicted in chart 4
.
One new goat case was reported in FY 2004. Approximately 3,058 animals
were indemnified comprised of 47% non-registered sheep, 44% registered
sheep, 6% non-registered goats and 1% registered goats. http://www.aphis.usda.gov/vs/nahps/scrapie/yearly_report/yearly-report.html TSS ############## BSE-L-subscribe-request@kaliv.uni-karlsruhe.de ##############
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