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From: TSS ()
Subject: BSE IN SHEEP Lord Vinson asked Her Majesty's Government
Date: March 18, 2008 at 11:44 am PST

Agriculture: BSE
Lord Vinson asked Her Majesty's Government:

In view of the conclusion of the Spongiform Encephalopathy Advisory
Committee in December 2006 that the prevalence of BSE in the United Kingdom
sheep population was likely to be zero and that the precautionary measure of
splitting sheep to remove the spinal cord was unnecessary, when they will
adopt the European Union-approved process of vacuum removal, as practised in
France and elsewhere; and how much this alternative method would benefit the
United Kingdom sheep and meat industry annually. [HL2116]

The Parliamentary Under-Secretary of State, Department of Health (Lord Darzi
of Denham): The Community TSE Regulations ((EC) 999/2001) lays down the
rules for prevention, control and eradication of certain transmissible
spongiform encephalopathies (TSE). This requires that the spinal cord of
sheep and goats over 12 months of age, or which have a permanent incisor
erupted, must be removed and stained and disposed of as specified risk
material (SRM). The Community regulation does not specify any method of
removal and no particular methods of removal are specifically European Union
approved.

We have been advised by the Food Standards Agency (FSA) that the latest
Spongiform Encephalopathy Advisory Committee (SEAC) advice on the prevalence
of bovine spongiform encephalopathy (BSE) in the United Kingdom sheep flock
is that it may be zero or in the worst case no more than 10 flocks would be
affected. SEAC has also advised of the importance of maintaining current SRM
controls in order to minimise public health risk were BSE ever to enter the
sheep flock and that a possible human health risk from atypical scrapie
(another TSE of sheep) cannot, at present, be ruled out. SEAC has not issued
any advice on the method of removal of spinal cord in sheep and goats.

We have also been advised that the FSA will be re-examining the
effectiveness of the suction method for removal of sheep spinal cord and the
possible methods of verification of complete removal. The agency will remain
in close contact with the industry during this re-evaluation of the issue.


http://www.publications.parliament.uk/pa/ld200708/ldhansrd/text/80310w0001.htm#08031025000002


Tissue distribution. For atypical scrapie, what is PrPres and
infectivity distribution within sheep of different genotypes,
particularly with respect to SRM removal? For classical
scrapie and experimental BSE in sheep, tissue distribution of
infectivity is widespread. Thus, even with SRM controls in
place, an infected sheep poses around 1000 times the risk to
human health than does an infected cow22. Does the
distribution depend on whether infection is by the oral or
intracerebral route? Are some VRQ sheep carriers with no
neurological symptoms?

21 Gubbins S. Prevalence of BSE in sheep: interpreting the results of
retrospective and
prospective testing of sheep TSE cases. SEAC 84 open meeting
22 paper presented to Food Standards Agency board on 9 December 2004.
http://www.foodstandards.gov.uk/multimedia/pdfs/fsa041204.pdf
Also see paper SEAC/84/2 Annex 2: McLean, A.
Page 13
© SEAC 27 February 2006

SEAC SHEEP SUBGROUP
POSITION STATEMENT


http://www.seac.gov.uk/pdf/positionstatement-sheep-subgroup.pdf

NOR-98 ATYPICAL SCRAPIE USA UPDATE AS AT OCT 2007
(documented now in 5 different states)

SCRAPIE PROGRAM FY REPORT 2007


Prepared by National Center for Animal Health Programs Ruminant Health
Programs Team November 15, 2007


snip...


Infected and Source Flocks


During FY 2007, there were a total of 76 new infected or source flocks
identified. Of those new flocks identified, 30 were infected flocks and 46
were source flocks (Figure 2). As of September 30, 2007, there were 38
scrapie infected and source flocks with open statuses (Figure 3). ...


snip...


In FY 2007, 331 scrapie cases have been confirmed and reported by the
National Veterinary Services Laboratories (NVSL), including 59* Regulatory
Scrapie Slaughter Surveillance (RSSS) cases (Figure 5 and Slide 16). In FY
2007, two field cases, one validation case, and two RSSS cases were
consistent with Nor-98 scrapie. The Nor98-like cases originated from flocks
in California, Minnesota, Colorado, Wyoming and Indiana respectively.
Nineteen cases of scrapie in goats have been reported since 1990 (Figure 6).
The last goat case was reported in September 2007.


snip...

see full report here ;

http://www.aphis.usda.gov/animal_health/animal_diseases/scrapie/downloads/yearly_report.pps

P03.141


Aspects of the Cerebellar Neuropathology in Nor98


Gavier-Widén, D1; Benestad, SL2; Ottander, L1; Westergren, E1
1National Veterinary Insitute, Sweden; 2National Veterinary Institute,
Norway


Nor98 is a prion disease of old sheep and goats. This atypical form of
scrapie was first
described in Norway in 1998. Several features of Nor98 were shown to be
different
from classical scrapie including the distribution of disease associated
prion protein
(PrPd) accumulation in the brain. The cerebellum is generally the most
affected brain
area in Nor98. The study here presented aimed at adding information on the
neuropathology in the cerebellum of Nor98 naturally affected sheep of
various
genotypes in Sweden and Norway. A panel of histochemical and
immunohistochemical
(IHC) stainings such as IHC for PrPd, synaptophysin, glial fibrillary acidic
protein,
amyloid, and cell markers for phagocytic cells were conducted. The type of
histological
lesions and tissue reactions were evaluated. The types of PrPd deposition
were
characterized. The cerebellar cortex was regularly affected, even though
there was a
variation in the severity of the lesions from case to case. Neuropil
vacuolation was
more marked in the molecular layer, but affected also the granular cell
layer. There was
a loss of granule cells. Punctate deposition of PrPd was characteristic. It
was
morphologically and in distribution identical with that of synaptophysin,
suggesting
that PrPd accumulates in the synaptic structures. PrPd was also observed in
the
granule cell layer and in the white matter. ***The pathology features of
Nor98 in the
cerebellum of the affected sheep showed similarities with those of sporadic
Creutzfeldt-Jakob disease in humans.


http://www.prion2007.com/pdf/Prion%20Book%20of%20Abstracts.pdf

typical scrapie transmits to primates by there NON-FORCED ORAL CONSUMPTION ;


76/10.12/4.6


http://www.bseinquiry.gov.uk/files/yb/1976/10/12004001.pdf


full text ;


http://nor-98.blogspot.com/


http://scrapie-usa.blogspot.com/


Caprine Scrapie Prevalence Study (CSPS)

CSPS was initiated in May 2007 to estimate the national prevalance of
scrapie in adult goats at slaughter. If no scrapie is found we will be able
to conclude that the prevalence in goats is greater than zero and less than
0.1 percent. AS of January 31, 2008, 2,942 goats have been sampled for
scrapie testing (1,515 in FY 2007 and 1,427 in FY 2008). Collection numbers
by quarter in FY 2008 is shown in Chart 8. To date, no goats have tested
positive for scrapie as part of this surveillance program. HOWEVER, THREE
POSITIVE GOATS have been identified this fiscal year through field
investigations. One was a clinical suspect submitted for testing and THE
OTHER TWO WERE MEMBERS OF THE OF THE BIRTH HERD OF THE CLINICAL CASE.


snip...


please see full text ;


http://www.aphis.usda.gov/animal_health/animal_diseases/scrapie/downloads/monthly_scrapie_rpt.pps

SPONGIFORM ENCEPHALOPATHY ADVISORY COMMITTEE
Draft minutes of the 99th meeting held on 14th December 2007


snip...


• A member explained that a confirmed case of atypical scrapie
had been recently identified in a research project at the
Institute of Animal Health (IAH). The animal had been born in
1997 in New Zealand, imported into the UK in 1998, spending
the first six months at the Arthur Rickwood Sheep Unit
(ARSU) before transfer to the IAH site at Compton. Thus, it is
possible it may have become infected either in New Zealand,
whilst at ARSU, where two other cases have now been
confirmed, or at Compton, perhaps as a result of the
experiments conducted during the research study involving
transfusion of blood between sheep. The case is under
further investigation.


• Members considered a report describing a case of
Creutzfeldt-Jakob Disease (CJD) of prion protein gene codon
129 VV genotype who had died in 2000 at the age of 39 years
old. The case had unusual neuropathological features and
abnormal prion protein (PrPSc) western blot banding pattern1.
One possible interpretation of these data was that this could
represent the first case of vCJD in an individual of VV
genotype. However, members noted that the clinical, cerebral
Magnetic Resonance Imaging and neuropathological features
were within the range previously observed with sporadic CJD
(sCJD). Although there were similarities between the
molecular features of PrPSc in the case and those of cases of
vCJD, they were not identical and only strain typing mouse
bioassays could provide conclusive evidence about the
causative transmissible spongiform encephalopathy (TSE)
agent. The paper stated that transmission studies of this
case, in transgenic mice, were being undertaken but there
was no information about the current status of these
experiments. The Chair asked the Acting Secretary to contact


1 Mead et al. (2007) Creutzfeldt-Jakob disease, prion protein gene codon
129VV, and
a novel PrPSc type in a young British women. Arch. Neurol. 64, 1780-1784.
5
© SEAC 2007


the research group to ask about such transmission
experiments.


• A member informed SEAC that the Department for
Environment, Food and Rural Affairs (Defra) was consulting
on cost and responsibility sharing for animal health and
welfare2 and that this included specific proposals for TSE
controls between government and industry.

snip...


11. Dr Danny Matthews (Veterinary Laboratories Agency [VLA]) noted
that all three of the atypical scrapie cases associated with ARSU
are of the Cheviot breed and two were homozygous and one was
heterozygous for the AFRQ allele. It was possible that the sheep
carrying this allele may be susceptible to atypical scrapie that
arises spontaneously.


2 Defra consultation on sharing costs and responsibility: animal health and
welfare.
http://www.defra.gov.uk/news/latest/2007/animal-1211.htm
6
© SEAC 2007


12. Members asked what measures might be taken to minimise the
spread of atypical scrapie at the site referred to in paragraph 15 of
the report and were informed that manure from the Unit had been
spread on adjacent farmland, which provided a source of straw of
the Unit. It had been suggested this practice might represent a
potential route for recycling of the atypical scrapie agent, and may
be inadvisable.


13. In relation to (ii), members noted there were four hypotheses for
the interpretation of the findings from passage of two sheep TSE
cases in mice: an experimental error had occurred, the features
observed may be a normal consequence of passage of classical
scrapie isolates in the breed and genotype of sheep, a strain
conversion may have occurred or the features observed may
reflect a mixed BSE-classical scrapie infection in sheep.


14. Dr Matthews explained that an internal audit had found no
evidence of experimental error but an independent audit was
planned with Professor Alun Williams as the scientific advisor. Dr
Jim Hope (VLA) explained that the suggestion that the features
observed on strain typing of two sheep TSE cases may be a
normal consequence of passage of classical scrapie isolates from
the particular breed and genotype of sheep, had arisen as one of
the cases was an ARQ/ARQ Swaledale. Sheep of this genotype
and breed rarely succumb to classical scrapie. Only one other
case of classical scrapie in an animal of this genotype and breed
had been strain typed by mouse bioassay with the features on
passage consistent with classical scrapie.


15. The Chair considered that of the four possibilities, the first two
appear to be the least likely, the third possibility may be the most
likely but is unproven and the fourth possibility cannot be excluded.
It is important to note that the features observed on mouse
bioassay are not consistent with features observed when BSE is
passaged in mice. If the findings did reflect a mixed BSE-classical
scrapie infection, the isolates were from historic sheep TSE cases
and the probability of mixed infections was low. Thus, there is no
indication from these data of a current significant risk to human
health from BSE in sheep.


16. A member asked why the report only considered mixed infections
of classical scrapie and BSE rather than atypical scrapie as it is
known that classical and atypical scrapie can occur together. The
Chair explained that as the report described the analysis of two
sheep TSE cases that discriminatory testing indicated were cases


7
© SEAC 2007


of classical scrapie, only mixed infections of classical scrapie and
BSE had been considered.


17. A member suggested that less certainty should be reflected in the
estimate of the probability of mixed infection arising (footnote 8 of
the draft report) as the estimates relied on an assumption that BSE
and classical scrapie would occur independently. In addition, it
was incorrect to state that the most likely prevalence of BSE in
sheep was zero (paragraphs 32 and 39 of the draft report); the
sample gives an estimate of the maximum prevalence that is
consistent with the results of the survey.

snip...


ITEM 5 – SCIENTIFIC BASIS OF CLASSICAL SCRAPIE CONTROLS
(SEAC 99/3)


21. Mr Andrew Gresham (Defra) gave an overview of the background
and policy context of the issue. The European Court of First
Instance had, following an application by the French Government
and, pending a full hearing, suspended clauses in new European
Commission legislation to allow sheep from classical scrapie
affected flocks to enter the human food chain if testing negative for
TSE. The UK intended to support the Commission at the full
hearing but wished to seek SEAC’s advice in relation to possible
links between classical scrapie and human TSEs and the
performance characteristics of discriminatory tests for sheep TSEs.
SEAC had been provided with the opinions of the French Food
Safety Authority (AFSSA), the European Food Safety Authority


(EFSA) and the German TSE advisory committee (KOM AG TSE)
8
© SEAC 2007


that had considered these issues. Advice from SEAC could be
incorporated into a UK submission to the Court.

22. A member noted that the AFSSA opinion reflected concerns that
as a consequence of the release of animals from classical scrapieaffected
sheep flocks into the human chain, cases of undiagnosed
BSE may also be inadvertently released into the food chain.
Furthermore, a greater number of classical scrapie infected sheep
may enter the food chain even though it is not possible to exclude
a risk to human health from classical scrapie. Three key
uncertainties had been identified by AFSSA, EFSA and KOM AG
TSE, although there were some differences in emphasis about the
uncertainties in the opinions. The uncertainties related to (i) the
capability of tests to detect TSEs in sheep during the stage when
PrPSc is accumulating in the periphery only, (ii) the ability of the
tests to detect BSE when another TSE is present and (iii) the
evidence suggesting a lack of link between human and animal
TSEs other than BSE. In relation to (iii), observations that classical
scrapie has been an endemic disease in sheep for more than 200
years without any apparent association with human disease, and
that sporadic Creutzfeldt-Jakob Disease (sCJD) exists in countries
such as Australia and New Zealand with no reported cases of
classical scrapie, are incontrovertible. However, it should be noted
that it would be very difficult to demonstrate an epidemiological link
between such relatively rare diseases in animals and humans.
Authors of two epidemiological studies3,4 that had examined risk
factors for sporadic Creutzfeldt-Jakob Disease (sCJD) dismissed a
link between classical scrapie and sCJD. However, these data
could be interpreted differently to suggest a potential link, this
could be a chance association arising from biases inherent in the
design of these retrospective studies. It was therefore important
not to be completely dismissive of a lack of a link as it would be
very difficult to prove an epidemiological link between such rare
diseases.


23. Members noted that, although there is no evidence for a risk to
human health from classical scrapie, a risk could never be ruled
out. However, even if there is a risk, the risk must be very small
indeed as the observed prevalence of sCJD is very low.


snip...


ITEM 8 – PUBLIC QUESTION AND ANSWER SESSION


40. The Chair explained that the purpose of the question and answer
session was to give members of the public an opportunity to ask
questions related to the work of SEAC. Mr Terry Singeltary
(Texas, USA) had submitted a question prior to the meeting,
asking: “With the Nor-98 now documented in five different states so
far in the USA in 2007, and with the two atypical BSE H-base


13
© SEAC 2007


cases in Texas and Alabama, with both scrapie and chronic
wasting disease (CWD) running rampant in the USA, is there any
concern from SEAC with the rise of sporadic CJD in the USA from
''unknown phenotype'', and what concerns if any, in relations to
blood donations, surgery, optical, and dental treatment, do you
have with these unknown atypical phenotypes in both humans and
animals in the USA? Does it concern SEAC, or is it of no concern
to SEAC? Should it concern USA animal and human health
officials?”


41. A member considered that this question appeared to be primarily
related to possible links between animal and human TSEs in the
USA. There is no evidence that sCJD is increasing in the USA and
no evidence of any direct link between TSEs and CJD in the USA.
Current evidence does not suggest that CWD is a significant risk to
human health. There are unpublished data from a case of human
TSE in the USA that are suggestive of an apparently novel form of
prion disease with distinct molecular characteristics. However, it is
unclear whether the case had been further characterised, if it could
be linked to animal TSEs or if other similar cases had been found
in the USA or elsewhere. In relation to the possible public health
implications of atypical scrapie, H-type BSE and CWD, research
was being conducted to investigate possible links and surveillance
was in place to detect any changes in human prion diseases.
Although possible links between these diseases and human TSEs
are of concern and require research, there is no evidence to
suggest immediate public health action is warranted. The possible
human health risks from classical scrapie had been discussed
earlier in the meeting. Members noted that there are effective
channels of discussion and collaboration on research between
USA and European groups. Members agreed it is important that to
keep a watching brief on new developments on TSEs.


ITEM 9 – UPDATE ON vCJD AND sCJD EPIDEMIOLOGY


42. Dr Richard Knight (NCJDSU) presented an update on the
epidemiology of cases of sCJD and vCJD in the UK and
elsewhere. Between May 1990 and October 2007, 944 cases of
sCJD had been identified in the UK with a mean age at onset of 66
(range 15-94) years and mean age of death of 67 (range 20-95)
years. There is no significant gender difference in sCJD incidence.
There had been a trend towards an increasing number of cases
over time to almost 80 cases per year in 2003; this increased trend
had also been observed in other countries and was considered to
be a result of better surveillance and diagnosis of disease. There
has been a decline in number since 2003, but this may not be of


15
© SEAC 2007


significance. The post mortem rate for sCJD referral is about 60%.
The genotype distribution of sCJD cases was 64% MM, 18% MV
and 18% VV at codon 129 of the prion protein gene.
43. Dr Knight explained that the total number of definite and probable
vCJD cases in the UK up to November 2007 was 166, with four
cases still alive. Three of out of four vCJD cases treated with
pentosan polysulphate (PPS) had appreciably longer survival
times, but it is not proven that this is the result of treatment. No
statistically significant gender difference had been observed in
vCJD cases. The age distribution of vCJD had not altered over the
course of the UK epidemic, with the median age of death of 30
(range 14-75) years. Statistical analysis of the UK incidence of
deaths from vCJD suggested the epidemic had peaked in 2000
with 28 deaths. There are three cases identified with onset in 2006
and four deaths in 2007. Geographical distribution of vCJD cases
in the UK shows higher incidence in the North than South. All 146
vCJD cases tested to date are of the MM genotype.
44. Dr Knight explained that elsewhere in the world up to November
2007, 39 vCJD cases have been reported with 23 in France, four in
the Republic of Ireland (RoI), three in the USA, two in the
Netherlands, two in Portugal and single cases in Italy, Canada,
Japan, Saudi Arabia and Spain. Infection is considered likely to
have occurred in the UK in two RoI cases, two USA cases, one
French case, the Japanese, and Canadian cases. One of the
French cases had a history of possibly significant residence in the
UK. One USA case is thought likely to have been exposed to
infection in Saudi Arabia, rather than the USA.


45. Dr Knight explained that the Transfusion Medicine Epidemiology
Review study had identified four instances of vCJD infection
resulting from receipt of non-leucodepleted red blood cells donated
by individuals who had subsequently developed vCJD. The donors
developed clinical vCJD ranging from 17 months to 3.5 years after
blood donation and this indicates that blood can be infective 3.5
years before the development of clinical disease. Clinical vCJD
was identified in three recipients (all of MM genotype) between 6.5
and 8.3 years after receipt of blood. The fourth recipient, who died
of non-neurological disease, with only lymphoreticular evidence of
vCJD infection was of MV genotype.


46. In response to a question about the neuropathology of the vCJD
case that died after receiving PPS, Dr Knight explained that no
autopsy was undertaken.


16
© SEAC 2007


47. A member asked about the reason for the increase in sCJD
detection in the year up to 2003. Dr Knight replied that it was
probably due to better awareness of the disease and the
availability of better diagnostic methods such as cerebrospinal fluid
testing and magnetic resonance imaging.


48. Mr Mark Noterman (Department of Health [DH]) asked whether the
neuropathological referrals rate had increased after the Chief
Medical Officer’s letter to clinicians earlier in the year to remain
vigilant about cases of neurological disease that could be related to
prion disease. Dr Knight replied that there had been no
subsequent significant increase in referral rate.


snip...


ITEM 11 – RE-ASSESSMENT OF THE POTENTIAL RISK OF vCJD
TRANSMISSION VIA DENTISTRY (SEAC 99/7)


59. Dr Bennett and Dr Peter Grove (DH) presented findings of an
interim assessment examining the risk that vCJD may be
transmitted via dental procedures. As there is a lack of substantial


19
© SEAC 2007


data with which to accurately quantify many of the key parameters
in the risk assessment, plausible ranges for parameters were
established to take account of the often large uncertainties in the
data. The key areas of uncertainty are infectivity in dental and oral
tissues of patients incubating vCJD, the level of protein residues on
dental instruments following decontamination, the efficacy of
autoclaving, the current prevalence of vCJD infection in the
population, and the epidemiology of vCJD. These uncertainties
strongly influence the quantification of the risk.
60. It was explained that many plausible scenarios built up using
ranges for each of these factors suggest that dental transmission
may have no detectable effect on the course of the vCJD epidemic.
However, there are some scenarios which include a combination of
pessimistic assumptions as regards the infectivity of dental/oral
tissues and the effects of instrument decontamination which
suggest that there could be some hundreds of vCJD transmissions
per annum via dentistry, albeit against a background of many
thousand existing subclinical vCJD infections, or where dental
transmission could generate a self-sustaining reservoir of vCJD
infection within the population. Should a large proportion of
secondary transmissions result in subclinical infections, either
never developing into clinical disease or doing so over an extended
time-scale, and such infections are infectious, the likelihood of a
self-sustaining epidemic increases. The proportion of individuals
that may be infected from having consumed BSE contaminated
food or from human to human transmission of vCJD that may enter
such a subclinical carrier state is unknown. Research to address
the key uncertainties is on-going and new data would enable some
of the assumptions underpinning these scenarios to be revised.
61. The committee welcomed the risk assessment, acknowledging it
had been developed in collaboration with a scientific reference
group of independent experts. Studies to address the scientific
uncertainties were considered important, particularly infectivity
studies on human oral and dental tissues from vCJD patients.
62. A member suggested that following secondary transmission, the
agent may adapt to become infectious to all prion protein
genotypes. Dr Grove noted that since the risk assessment
considers four scenarios ranging from one in which no secondary
infection develops into clinical disease to one in which everyone
who is infected develops clinical disease, this possibility is
considered.


20
© SEAC 2007


63. Members noted that there were two obvious precautionary
measures that could be put in place to dramatically reduce the
potential risk of vCJD transmission via dental procedures: making
endodontic files and reamers single use, which was implemented
in April 2007 and improving instrument decontamination using
current technologies. A 0.5 – 1.0 log reduction in infectivity from
improved decontamination practice could remove the risk of a self
sustaining epidemic. It is very important, therefore, that DH
ensures dentists do adopt good practice throughout the profession
and that this is audited. Introduction of consistent decontamination
practices would also reduce the observed variability of instrument
contamination, and thus reduce the risk of local outbreaks of
transmission.


64. Mr Barry Cockcroft (Chief Dental Officer, DH) noted that the effect
of the guidance on making endodontic files and reamers single use
had been included in the risk assessment. There is good evidence
that dentists are adhering to the guidance. A survey by DH
Regional Directors of Public Health could not find any dentists who
are unaware of the Chief Dental Officer’s Professional Letter
advising that files and reamers should be treated as single use
only, and dental instrument suppliers have reported that sales of
files and reamers have increased dramatically since the guidance
was issued. A draft Health Technical Memorandum would be
issued for consultation in early 2008 designed specifically for
dental practitioners and their staff as a comprehensive guide to
best practice. An audit tool will be available to help dentists assess
their own compliance with the guidance and to enable DH to
assess whether new guidance is working in practice. Dental
nurses will now also be regulated and registered with the General
Dental Council.


snip...end...full text ;


http://www.seac.gov.uk/minutes/99.pdf


SEAC 99th meeting on Friday 14th December 2007


http://seac992007.blogspot.com/

TSS




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