No temporal trends in the prevalence of atypical scrapie in British sheep, 2002-2006
K. Marie McIntyre1§, Victor J. del Rio Vilas2 and Simon Gubbins1 1Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Surrey GU24 0NF, UK
2Centre for Epidemiology and Risk Analysis, Veterinary Laboratories Agency, Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK §Corresponding author Email addresses: KMM: marie.mcintyre@bbsrc.ac.uk VDRV: v.delriovilas@vla.defra.gsi.gov.uk SG: simon.gubbins@bbsrc.ac.uk
- 2 -
Abstract
Background
So-called atypical scrapie was first identified in Great Britain (GB) in 2002 following the introduction of wide-scale scrapie surveillance. In particular, abattoir and fallen stock surveys have been carried out in GB since 2002, with a total of 147 atypical positives identified by the end of 2006. The results of these surveys provide data with which to assess temporal trends in the prevalence of atypical scrapie in sheep in Great Britain between 2002 and 2006.
Results
Using the results of abattoir and fallen stock surveys, the prevalence of atypical scrapie (percentage of samples positive) was estimated. The prevalence in the abattoir and fallen stock surveys, for all years combined, was 0.09% (95% confidence interval (CI): 0.08%- 0.11%) and 0.07% (95% CI: 0.05%-0.11%), respectively. There were no significant temporal trends in either survey. Comparing the surveys’ results, there were no significant differences in annual prevalence or the prevalence within PrP genotypes. For the abattoir survey, the PrP genotype with the highest prevalence was AHQ/AHQ, which was significantly higher than all other genotypes, except ARR/AHQ, AHQ/ARH and ARH/ARQ.
Conclusions
The estimated prevalence of atypical scrapie was similar in both the abattoir and fallen stock surveys. Our results indicate there was no significant temporal trend in prevalence, adding to evidence that this atypical form of scrapie may be a sporadic condition or, if it is infectious, that the force of infection is very low.
snip...
Conclusions
The results of this study indicate that the prevalence of atypical scrapie did not change significantly between 2002 and 2006. Furthermore, it did not differ significantly between the abattoir and fallen stock surveys, which is not the case for classical scrapie. The absence of temporal trends in the prevalence of atypical scrapie adds to evidence that this may be a sporadic condition or, if it is infectious, the force of infection is very low. Recent experimental work has demonstrated that atypical scrapie is transmissible [33], but the evidence for whether or not it is infectious is mixed. Examination of demographic factors and trading patterns has suggested transmission of atypical scrapie could be occurring, albeit slowly [34] , suggesting it could be infectious. By contrast, a case control study of Nor98 in Norway found no risk factors to indicate transmission between flocks [35], suggesting atypical scrapie is sporadic. Ultimately, a combination of evidence from case-control studies, spatio-temporal analysis and laboratory experiments will be necessary to determine whether this disease is infectious or sporadic in nature. A similar approach was utilised in the case of arguments surrounding sporadic- versus variant-Creutzfeldt-Jakob disease [36].
http://www.biomedcentral.com/content/pdf/1746-6148-4-13.pdf
PLEASE note, in my opinion, there is absolutely no proof of or evidence what so ever of a natural field case of a spontaneous and or sporadic TSE in any species, anywhere.
WHY is it not possible for the potential of atypical scrapie transmitting the same way as typical scrapie ???
WHY is feed not a factor here ???
EVIDENCE OF SCRAPIE IN SHEEP AS A RESULT OF FOOD BORNE EXPOSURE
This is provided by the statistically significant increase in the incidence of sheep scrape from 1985, as determined from analyses of the submissions made to VI Centres, and from individual case and flock incident studies. ........
http://www.bseinquiry.gov.uk/files/yb/1994/02/07002001.pdf
STRICTLY PRIVATE AND CONFIDENTIAL 25, AUGUST 1995
snip...
To minimise the risk of farmers' claims for compensation from feed compounders.
To minimise the potential damage to compound feed markets through adverse publicity.
To maximise freedom of action for feed compounders, notably by maintaining the availability of meat and bone meal as a raw material in animal feeds, and ensuring time is available to make any changes which may be required.
snip...
THE FUTURE
4..........
MAFF remains under pressure in Brussels and is not skilled at handling potentially explosive issues.
5. Tests _may_ show that ruminant feeds have been sold which contain illegal traces of ruminant protein. More likely, a few positive test results will turn up but proof that a particular feed mill knowingly supplied it to a particular farm will be difficult if not impossible.
6. The threat remains real and it will be some years before feed compounders are free of it. The longer we can avoid any direct linkage between feed milling _practices_ and actual BSE cases, the more likely it is that serious damage can be avoided. ...
SEE full text ;
http://www.bseinquiry.gov.uk/files/yb/1995/08/24002001.pdf
TAFS INTERNATIONAL FORUM FOR TRANSMISSIBLE ANIMAL DISEASES AND FOOD SAFETY a non-profit Swiss Foundation (May 16, 2007) TAFS1 Position Paper on Atypical scrapie and Atypical BSE
Although most atypical cases occur singly in flocks, there are some instances where two affected sheep have been identified in flocks. This may indicate that natural transmission may occur, or that the sheep were infected from a common alternative source(22, 29). Possible indications of an association with the feeding of vitamins and mineral feed supplements were detected in Norway, but remain to be proven(22).
snip...
Atypical BSE may arise spontaneously in a small proportion of cattle. The existence of sporadic CJD in humans has led to postulation that disease could arise spontaneously in any animal, but this is still not proven to happen. Despite the small numbers of atypical BSE detected so far, in some countries the numbers are too great to suggest that they all arise spontaneously, if it were assumed that such aphenomenon occurred at the same frequency as sporadic CJD in humans.
http://www.tseandfoodsafety.org/position_papers/TAFS_POSITION_PAPER_ON_ATYPICAL_SCRAPIE_AND_%20ATYPICAL_BSE_070516.pdf
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
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
intracerebral route? Are some VRQ sheep carriers with no neurological symptoms?
SEAC SHEEP SUBGROUP POSITION STATEMENT
http://www.seac.gov.uk/pdf/positionstatement-sheep-subgroup.pdf
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
High incidence of subclinical infection of lymphoid tissues in scrapie-affected sheep flocks
Our findings indicate that contamination of the environment plays an important part in sustaining the infection.
http://www.springerlink.com/content/u761171744280806/
http://scrapie-usa.blogspot.com/2008/03/high-incidence-of-subclinical-infection.html
NOR-98 ATYPICAL SCRAPIE USA UPDATE AS AT OCT 2007
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
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6997404&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus
full text ;
SCRAPIE TYPICAL AND ATYPICAL USA
ATYPICAL NOR-98 SCRAPIE
LOCATION UPDATE ON 5 DOCUMENTED CASES THIS YEAR ;
The flocks of origin are WY, CO, CA, IN, and MN.
personal communication USDA et al. ...TSS
http://nor-98.blogspot.com/
http://scrapie-usa.blogspot.com/
TSS
Saturday, April 5, 2008
Tuesday, March 11, 2008
BSE IN SHEEP Lord Vinson asked Her Majesty's Government
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
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
Tuesday, March 4, 2008
Fw: [BSE-L] SCRAPIE DOCUMENTED IN CLINICAL SUSPECT GOAT, WITH TWO MORE DOCUMENTED IN SAME BIRTH HERD OF CLINICAL CASE
SCRAPIE USA UPDATE MONTHLY REPORT JANUARY 2008
prepared February 20, 2008
Infected and Source Flocks
There were 27 scrapie infected and source flocks with open statuses (Figure 3) as of January 31, 2008. Two new source flocks and one new infected flock were reported in January (Figure 4) with a total of 22 reported for FY 2008 (Figure 5). ....
snip...
Positive Scrapie Cases
As of January 31, 2008, 58 new scrapie cases have been confirmed and reported by the National Veterinary Services Laboratories (NVSL) in FY 2008 (Figure 7). Of these, 52 were field cases and 6* were Regulatory Scrapie Slaughter Surveillance (RSSS) cases (collected in FY 2008 and reported by February 20, 2008). There were 8 positive cases for January which are depicted in Figure 8. Seventeen cases of scrapie in goats have been confirmed by NVSL since implementation of the regulatory changes in FY 2002 (Figure 9). The most recent positive goat cases were from the SAME HERD and WERE BOTH CONFIRMED IN JANAURY 2008.
snip...
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
PLEASE NOTE OUT OF SIGHT, OUT OF MIND REPORT atypical Scrapie NOR-98 CASES USA
IT seems that if they do not discuss, and or report on there scrapie page, the 5 documented ATYPICAL NOR-98, in 5 different states in 2007, it's seems they think that all will forget. However, I am here to tell you this will not happen. or the fact that the atypical scrapie NOR-98 is more virulent and resembles that of the sporadic CJD in humans. nope, we cannot forget this either. I have spoken with the USDA, APHIS, VS last year about making a separate map in their PPS presentation to show how many, and where these atypical scrapie NOR-98 cases are documented.
Their reply ;
TSS QUESTION - AND, if these are new cases, and i understand this correctly, how do we know what state they were reported in ?
USDA, APHIS, VS ANSWER - you can't from the report. The flocks of origin were in WY, CO and CA
TSS SUGGESTION - maybe you might can add these atypical cases to the pps presentation on the monthly chart some how,.... just a suggestion ?
USDA, APHIS, VS ANSWER - We are considering it.
==================================
SINCE THEN, two more documented atypical scrapie NOR-98 cases have been documented in two more states ;
ATYPICAL NOR-98 SCRAPIE LOCATION UPDATE ON 5 DOCUMENTED CASES THIS YEAR ;
The flocks of origin are WY, CO, CA, IN, and MN.
personal communication USDA et al. ...TSS
snip...
INFECTED AND SOURCE FLOCKS AS of August 31, 2007, there were 33 scrapie infected and source flocks with open statuses (Figure 3). Five new source flocks and one new infected flock were reported n August (Figure 4) with a total of 64 reported for FY 2007(Figure 5).
snip...
IN FY 2007 TWO FIELD CASES, ONE VALIDATION CASE, AND TWO RSSS CASES WERE CONSISTENT WITH NOR-98 SCRAPIE. ...
(BRINGS A TOTAL OF 5 NOR-98 CASES DOCUMENTED IN 2007 IN USA. ...TSS)
http://www.aphis.usda.gov/animal_health/animal_diseases/scrapie/downloads/monthly_scrapie_rpt.pps
TAFS
INTERNATIONAL FORUM FOR TRANSMISSIBLE ANIMAL DISEASES AND FOOD SAFETY
a non-profit Swiss Foundation
(May 16, 2007)
TAFS1 Position Paper on Atypical scrapie and Atypical BSE
Although most atypical cases occur singly in flocks, there are some instances where two affected sheep have been identified in flocks. This may indicate that natural transmission may occur, or that the sheep were infected from a common alternative source(22, 29). Possible indications of an association with the feeding of vitamins and mineral feed supplements were detected in Norway, but remain to be proven(22).
snip...
Atypical BSE may arise spontaneously in a small proportion of cattle. The existence of sporadic CJD in humans has led to postulation that disease could arise spontaneously in any animal, but this is still not proven to happen. Despite the small numbers of atypical BSE detected so far, in some countries the numbers are too great to suggest that they all arise spontaneously, if it were assumed that such a phenomenon occurred at the same frequency as sporadic CJD in humans.
http://www.tseandfoodsafety.org/position_papers/TAFS_POSITION_PAPER_ON_ATYPICAL_SCRAPIE_AND_%20ATYPICAL_BSE_070516.pdf
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
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
intracerebral route? Are some VRQ sheep carriers with no neurological symptoms?
SEAC SHEEP SUBGROUP POSITION STATEMENT
http://www.seac.gov.uk/pdf/positionstatement-sheep-subgroup.pdf
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
NOR-98 ATYPICAL SCRAPIE USA UPDATE AS AT OCT 2007
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
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6997404&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus
full text ;
http://nor-98.blogspot.com/
http://scrapie-usa.blogspot.com/
TSS
prepared February 20, 2008
Infected and Source Flocks
There were 27 scrapie infected and source flocks with open statuses (Figure 3) as of January 31, 2008. Two new source flocks and one new infected flock were reported in January (Figure 4) with a total of 22 reported for FY 2008 (Figure 5). ....
snip...
Positive Scrapie Cases
As of January 31, 2008, 58 new scrapie cases have been confirmed and reported by the National Veterinary Services Laboratories (NVSL) in FY 2008 (Figure 7). Of these, 52 were field cases and 6* were Regulatory Scrapie Slaughter Surveillance (RSSS) cases (collected in FY 2008 and reported by February 20, 2008). There were 8 positive cases for January which are depicted in Figure 8. Seventeen cases of scrapie in goats have been confirmed by NVSL since implementation of the regulatory changes in FY 2002 (Figure 9). The most recent positive goat cases were from the SAME HERD and WERE BOTH CONFIRMED IN JANAURY 2008.
snip...
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
PLEASE NOTE OUT OF SIGHT, OUT OF MIND REPORT atypical Scrapie NOR-98 CASES USA
IT seems that if they do not discuss, and or report on there scrapie page, the 5 documented ATYPICAL NOR-98, in 5 different states in 2007, it's seems they think that all will forget. However, I am here to tell you this will not happen. or the fact that the atypical scrapie NOR-98 is more virulent and resembles that of the sporadic CJD in humans. nope, we cannot forget this either. I have spoken with the USDA, APHIS, VS last year about making a separate map in their PPS presentation to show how many, and where these atypical scrapie NOR-98 cases are documented.
Their reply ;
TSS QUESTION - AND, if these are new cases, and i understand this correctly, how do we know what state they were reported in ?
USDA, APHIS, VS ANSWER - you can't from the report. The flocks of origin were in WY, CO and CA
TSS SUGGESTION - maybe you might can add these atypical cases to the pps presentation on the monthly chart some how,.... just a suggestion ?
USDA, APHIS, VS ANSWER - We are considering it.
==================================
SINCE THEN, two more documented atypical scrapie NOR-98 cases have been documented in two more states ;
ATYPICAL NOR-98 SCRAPIE LOCATION UPDATE ON 5 DOCUMENTED CASES THIS YEAR ;
The flocks of origin are WY, CO, CA, IN, and MN.
personal communication USDA et al. ...TSS
snip...
INFECTED AND SOURCE FLOCKS AS of August 31, 2007, there were 33 scrapie infected and source flocks with open statuses (Figure 3). Five new source flocks and one new infected flock were reported n August (Figure 4) with a total of 64 reported for FY 2007(Figure 5).
snip...
IN FY 2007 TWO FIELD CASES, ONE VALIDATION CASE, AND TWO RSSS CASES WERE CONSISTENT WITH NOR-98 SCRAPIE. ...
(BRINGS A TOTAL OF 5 NOR-98 CASES DOCUMENTED IN 2007 IN USA. ...TSS)
http://www.aphis.usda.gov/animal_health/animal_diseases/scrapie/downloads/monthly_scrapie_rpt.pps
TAFS
INTERNATIONAL FORUM FOR TRANSMISSIBLE ANIMAL DISEASES AND FOOD SAFETY
a non-profit Swiss Foundation
(May 16, 2007)
TAFS1 Position Paper on Atypical scrapie and Atypical BSE
Although most atypical cases occur singly in flocks, there are some instances where two affected sheep have been identified in flocks. This may indicate that natural transmission may occur, or that the sheep were infected from a common alternative source(22, 29). Possible indications of an association with the feeding of vitamins and mineral feed supplements were detected in Norway, but remain to be proven(22).
snip...
Atypical BSE may arise spontaneously in a small proportion of cattle. The existence of sporadic CJD in humans has led to postulation that disease could arise spontaneously in any animal, but this is still not proven to happen. Despite the small numbers of atypical BSE detected so far, in some countries the numbers are too great to suggest that they all arise spontaneously, if it were assumed that such a phenomenon occurred at the same frequency as sporadic CJD in humans.
http://www.tseandfoodsafety.org/position_papers/TAFS_POSITION_PAPER_ON_ATYPICAL_SCRAPIE_AND_%20ATYPICAL_BSE_070516.pdf
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
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
intracerebral route? Are some VRQ sheep carriers with no neurological symptoms?
SEAC SHEEP SUBGROUP POSITION STATEMENT
http://www.seac.gov.uk/pdf/positionstatement-sheep-subgroup.pdf
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
NOR-98 ATYPICAL SCRAPIE USA UPDATE AS AT OCT 2007
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
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6997404&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus
full text ;
http://nor-98.blogspot.com/
http://scrapie-usa.blogspot.com/
TSS
Friday, February 15, 2008
SCRAPIE and TSE to human UPDATE 2008 (ambiguous terms of transition and reality set in)
SCRAPIE and TSE to human UPDATE 2008 (ambiguous terms of transition and reality set in)
The EFSA Journal (2008) 626, 1-11
© European Food Safety Authority, 2008
Scientific and technical clarification in the interpretation and consideration of some facets of the conclusions of its Opinion of 8 March 2007 on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals1
Scientific Report of the Scientific Panel on Biological Hazards
January 2008 - 37th Plenary meeting
Question EFSA-Q-2007-193
PANEL MEMBERS
Olivier Andreoletti, Herbert Budka, Sava Buncic, Pierre Colin, John D Collins, Aline De Koeijer, John Griffin, Arie Havelaar, James Hope, Günter Klein, Hilde Kruse, Simone Magnino, Antonio Martínez López, James McLauchlin, Christophe Nguyen-The, Karsten Noeckler, Birgit Noerrung, Miguel Prieto Maradona, Terence Roberts, Ivar Vågsholm, Emmanuel Vanopdenbosch.
ACKNOWLEDGEMENTS
The European Food Safety Authority wishes to thank the members of the Working Group for their contribution to this Scientific and Technical clarification: Olivier Andreoletti, Herbert Budka, Martin Groschup, James Hope, Danny Matthews, Marion Simmons, Emmanuel Vanopdenbosch (Chairman) and Kathy Webster.
1 For citation purposes: Scientific Report of the Panel on Biological Hazards on a request from the European Commission on “Scientific and technical clarification in the interpretation and consideration of some facets of the conclusions of its Opinion of 8 March 2007 on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals”. The EFSA Journal (2008), 626, 1-11. The EFSA Journal (2008) 626, 2-11
INTRODUCTORY STATEMENT FROM THE MEMBERS OF THE PANEL ON BIOLOGICAL HAZARDS ON COMMUNICATING SCIENTIFIC UNCERTAINTY
Scientific uncertainty results usually from five characteristics of the scientific method (EC, 2000): the variable chosen, the measurements made, the samples drawn, the models used and the causal relationship employed. This may also arise from a controversy on existing data or lack of some relevant data. Following appropriate scientific risk assessment, the expression of such uncertainty in complex settings, by simple and concise wording without sacrificing scientific exactness, is one of the major challenges of risk communication.
The following report is strictly limited to replying to the terms of reference as received from the European Commission by re-addressing the uncertainties that were reflected in the conclusions of the concerned EFSA 2007 opinion.
ANSWERS TO THE TERMS OF REFERENCE
1. In relation to conclusion 2 in page 7 the Authority is invited to clarify and substantiate if there is at this stage any scientific evidence about the presence of TSEs agents other than BSE, Classical and Atypical Scrapie agents in ovine or caprine animals.
Conclusion 2 in page 7 of the EFSA 2007 opinion states that: “The BSE agent is the only TSE agent identified as zoonotic. However, in view of their diversity it is currently not possible to exclude transmissibility to humans of other animal TSE agents.”
In the preamble of the EFSA 2007 opinion it is stated that:
• “Any positive case of TSE in small ruminants is termed as “TSE in small ruminants” which encompasses Classical Scrapie, Atypical Scrapie including Nor98 in sheep and goats as well as BSE in these species if found.”
It should be noted that, under 3.2.1 of the EFSA 2007 opinion it is stated that:
• “The introduction of active surveillance programmes in the European Union has led to the recognition of isolates that do not conform to previous phenotypes of BSE in cattle and Classical Scrapie in sheep. These are currently termed for operational reasons as “Atypical” BSE or Scrapie, but probably reflect part of a wider spectrum of isolates not previously recognised, and in the case of Atypical Scrapie affecting genotypes highly resistant to clinical Scrapie (Biacabe et al., 2004; Casalone et al., 2004; Benestad et al., 2003; Gavier- Widen et al., 2004; Buschmann et al., 2004).” Scrapie is a disease of ovine and caprine animals caused by a variety of TSE agents harbouring different biological properties that are still incompletely characterised, rather than by one specific transmissible entity. ‘Classical Scrapie’ and ‘Atypical Scrapie’ are operational rather than purely biological terms. (EFSA, 2005; Saegerman et al., 2007;
Benestad et al., 2008). The EFSA Journal (2008) 626, 3-11
Further on the EFSA 2007 opinion, under 3.2.3 the Panel acknowledges that there is a:
• “[…] lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents […]”
This is in accordance to the approach taken by the Panel in the EFSA 2005 opinion when classifying the possible TSE cases in small ruminants. In fact, the EFSA 2007 opinion stresses that:
• “Practical definitions of TSE in small ruminants are summarized in the EFSA opinion on the classification of Atypical and Classical Scrapie and BSE in small ruminants (EFSA, 2005) in the Table “Criteria for the categorisation of TSEs in small ruminants” (in annex 1 of the said EFSA opinion).”
In Annex 1 of the EFSA 2005 opinion, a table for the categorisation of TSEs in small ruminants can be found. This opinion concludes that the definition of Atypical Scrapie:
• “[…] is provided in juxtaposition with similar definitions for Scrapie and BSE in small ruminants. Sub-categorisation of Scrapie and Atypical Scrapie is premature although this may become possible when more data are available.” Recent studies have identified TSE agents in cattle that differ from the original TSE agent type, which causes the disease commonly known as BSE that was detected since 1986 in the United Kingdom and is referred to as ‘Classical BSE’ in this document.
Based on their diagnostic phenotypes these more recently identified TSE agents in cattle are called L- and H-type BSE agents (Biacabe et al., 2004; Casalone et al., 2004; Baron et al., 2007). In conclusion, the reply to the ToR number 1 is:
• In ovine animals, no TSE agents other than those causing Classical Scrapie and Atypical Scrapie have been identified.
• In caprine animals, no TSE agents other than those causing BSE, Classical Scrapie and Atypical Scrapie have been identified.
• The operational term ‘BSE’ covers a TSE of bovine animals that could be caused by at least three distinct TSE agents with heterogeneous biological properties.
• The operational term ‘Classical Scrapie’ covers a TSE of ovine and caprine animals caused by several TSE agents with heterogeneous biological properties.
• The operational term ‘Atypical Scrapie’ covers a TSE of ovine and caprine animals that differs from Classical Scrapie. Currently, it is a subject for debate whether it is caused by one or more TSE agents. The EFSA Journal (2008) 626, 4-11
2. In relation to conclusion 2 in page 7 the Authority is invited to specify the scientific evidences which do not allow to exclude transmissibility to humans of “other TSE agents” other than BSE. Conclusion 2 in page 7 of the EFSA 2007 opinion states that: “The BSE agent is the only TSE agent identified as zoonotic. However, in view of their diversity it is currently not possible to exclude transmissibility to humans of other animal TSE agents.”
In the EFSA 2007 opinion under 3.2.3. the Panel states that:
• “There are significant uncertainties associated with the question whether TSE agents in their whole spectrum may cross the human transmission barrier under natural conditions”.
This statement is supported both by scientific evidence and considerations, referenced in the EFSA 2007 opinion:
• Scientific evidence from transmission studies to primates: - Transmission of Classical Scrapie from a TSE agent adapted in hamster was demonstrated by oral challenge in squirrel monkey (Saimiri sciureus) (Gibbs et al., 1980);
- Transmission of Classical Scrapie from two distinct sheep sources by intracerebral challenge in cynomologus monkey (Macaca fascicularis) and marmoset monkey (Callithrix jacchus) (Gibbs and Gajdusek, 1972; Baker et al., 1988).
• Scientific considerations on TSE epidemiology: - “The assumed lack of association between TSEs in humans and those in small ruminants […] may be biased by a number of factors: (i) The lack of a data on the historical real prevalence and distribution of small ruminant TSEs, at a time where only passive surveillance was performed; (ii) the lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents; (iii) the lack of understanding of the diversity of TSEs in humans due to the limited molecular and bioassay characterisation of human TSEs also in relation to the number and spectrum of neurodegenerative diseases of humans; (iv) the predicted phenotype of disease that might arise should an animal derived TSE transmit to humans.” The EFSA Journal (2008) 626, 5-11
Further evidence is provided by:
• In vitro conversion assays: Raymond et al. (1997) studied whether there is a correlation between in vitro conversion efficiencies and known transmissibility of BSE, sheep Scrapie and CJD, and found limited conversion of human PrP-sen to PrP-res driven by PrP-res associated with both Scrapie (PrPSc) and BSE (PrPBSE). They concluded that “the inherent ability of these infectious agents of BSE and Scrapie to affect humans following equivalent exposure may be finite but similarly low”. Nevertheless, uncertainty arises from the fact that this is a simple in vitro model of a complex in vivo situation.
• Laboratory transmission studies with animal models: Since the publication of the Opinion new data have become available with regards to L type of BSE, which has now been identified in various EU members states (Biacabe et al., 2004; Casalone et al., 2004; Baron et al., 2007). This TSE agent, differing from that causing Classical BSE by its biochemical signature and transmission features in mouse models, has been transmitted to a Tg mouse model expressing Human M129 PRP gene (Beringue et al. 2007)2. Here again, uncertainty arises from the limitations of these animal models for the estimation of the human species barrier. These ‘proof of principle’ experiments provide data supporting the ability of TSE agents other than those causing Classical BSE to cross the human species barrier.
Even so, it is important to remember that as mentioned in the EFSA 2007 opinion, transmission to primates:
• “… does not allow to take into account the human gene PRNP polymorphisms (in particular the M/V 129), that have been identified to play a major role on relative susceptibility towards prion disease. In addition, genes other than the PrP gene may also be influential in determining overall susceptibility to TSEs.” Despite the interests in the area, studies of the transmissibility of currently known TSE agents using animal models will remain incomplete for several years.
In conclusion, the reply to the ToR number 2 is:
• Experimental transmissions to primate and to transgenic (Tg) mouse models expressing the human PrP gene, are currently used as to evaluate the potential capacity of a TSE agent to cross the human species barrier.
• TSE agents other than the Classical BSE agent from three field TSE cases (two Classical Scrapie cases and one L type BSE case) have been demonstrated to cross the modelled human species barrier.
• Some limitations to these models have to be considered, which include:
(i) The uncertainty of how well they represent the human species barrier. (ii) The uncertainty of how well the experimental inoculation route employed represents exposure under natural conditions. 2 Transmission of this TSE agent by intracerebral challenge to primates (Macaques) has been reported by Comoy et al. at the 2006 Prion Congress held in Torino. A scientific paper reporting this finding has been submitted for peer review publication. The EFSA Journal (2008) 626, 6-11
3. In relation to conclusion 3 in page 7, the Authority is invited:
a. To clarify if, although the diagnostic sensitivity and specificity of the discriminatory tests can not be assumed to be perfect, they are at this moment the diagnostic tool fit for the differentiation of the different TSE strains which can be present in ovine and caprine animals if they are performed according to the procedure described in point 3.2 (c) of Chapter C of Annex X to Regulation (EC) 999/2001.
Clarification of the ToR 3.a.: During the discussion of the WG it was clarified with the Commission services that when referring to differentiation of different TSE strains it was meant “identification of the TSE agent that causes Classical BSE versus any other TSE agent that can be present in ovine or caprine animals”.
Conclusion 3 in page 7 of the EFSA 2007 opinion states that:
• “Current discriminatory tests as described in the EC legislation to be used for discrimination between Scrapie and BSE appear, up to now, to be reliable for the differentiation of BSE from Classical and Atypical Scrapie. However, at the current stage of scientific knowledge, neither their diagnostic sensitivity nor their specificity can be assumed to be perfect.” Characterisation of TSE agents is based on biological and/or molecular methods. Molecular methods are based on the properties of the disease-specific proteaseresistant fragments of PrPSc or physico-chemical behaviour (e.g. proteinase K cleavage site, PrPSc glycosylation, relative proteinase K resistance, molecular conformation, etc). Biological methods identify the reproducibility and stability of the disease phenotype, including lesion profile and incubation period, on serial transmission in a specified mouse line, but also consider the phenotype of the disease in the host species. Discriminatory biochemical tests, as referred here, only represent a group of standardised methods (reagent protocols) allowing reproducible identification of certain abnormal PrP biochemical features associated with the TSE agent causing Classical BSE experimentally propagated in sheep. These biochemical methods cannot be considered to be appropriate tools for the differentiation of the different TSE agents (excluding the agent that causes Classical BSE), which can be present in ovine and caprine animals in the wider sense, as they have not been designed for that purpose.
In page 7 of the EFSA 2007 opinion, it is stated that based on the EFSA Opinion of 25 January 2007 on Quantitative Risk Assessment on the residual BSE risk in sheep meat and meat products (EFSA-Q-2005-235),
• “The Scrapie/BSE discriminatory tests are robust judging by their performance against a small number of samples in a blinded ring trial organised by the EU TSE Community Reference Laboratory (Stack et al., in preparation) and their application as part of small ruminant surveillance was continuing to improve the accuracy of these prevalence estimates. However, balanced against this optimistic scenario, the BIOHAZ Panel accepted that the sensitivity and specificity of the discriminatory tests had, for logistical reasons, not been experimentally evaluated and potential confounding factors, such as
The EFSA Journal (2008) 626, 7-11
concomitant infection of the same animal with Scrapie and BSE, remained to be investigated.” The result of that ring trial employing a limited number of different categories of samples3shows that all tests were able to discriminate between field cases of Classical Scrapie in sheep and the types of BSE in sheep available from experimental animals (Stack et al., 2008).
Moreover, it should be noted that as previously reported under 3.2.3 of the 2007 EFSA opinion, the Panel acknowledged that there is a:
• “[…]lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents […]”
In field cases of Classical Scrapie, more than one TSE agent can be isolated from a single animal (Pattison et al., 1961; Bruce, et al., 2002). The presence of one TSE agent can mask the presence of another as well as its manifestation with disease, when co-infecting the same individual. This phenomenon of “interference” has been studied in experimental models using different TSE agents (Manuelidis and Lu, 2003; Nishida et al., 2005; Bartz et al., 2007). Data reported by Baron and Biacabe (2001) indicated that intracerebral inoculation of C57Bl6 mice with a mixture of Scrapie and BSE agents, which were both already adapted to this mouse strain (i.e. species barrier effects had been ablated), resulted in the development of a TSE which presented with a Scrapie Western blot profile. Despite the fact that direct extrapolation of these observations to small ruminants is not possible, these results raise the possibility that the presence of BSE in sheep, if it occurred as a co-infecting TSE agent following established Scrapie, may remain undetected. As the likelihood of such a situation is uncertain at this moment, experiments designed to answer specifically to this question are currently ongoing in an EU funded program (QLK – CT –2001- 01309 BSE in sheep). The Panel recognises the uncertainty of performance of the discriminatory tests applied to small ruminants but also that it is pivotal to have some estimate of the likelihood of co-infection of BSE and Scrapie in the same animal. This would aid the understanding of the practical impact of this uncertainty.
In conclusion, the reply to the ToR number 3.a. is:
• Based on the limited data available, the discriminatory tests as implemented at EU level are practicable tools for screening of field TSE cases (as mentioned in Regulation 999/2001, Annex X, Chapter C, point 3.2. (c)), fulfilling the objective of rapid and reproducible identification of TSE cases that have a signature compatible with Classical BSE agent.
• These discriminatory tests cannot be considered to be perfect because of the current lack of understanding of both the true biodiversity of TSE agents in ovine and caprine animals and how the agents interact in case of co-infection. 3 These were: 4 Ovine BSE samples from ovine oral primary challenge with bovine BSE brain; 10 Ovine BSE samples, from intracerebral challenge with Cheviot AHQ/AHQ ovine BSE (1st sheep to sheep challenge); 12 Sheep Scrapie, positive by statutory tests; 9 Scrapie clinical suspects, negative by statutory tests; 2 Control sheep, negative samples; 2 confirmed bovine BSE positives; 2 Bovine negative controls.
The EFSA Journal (2008) 626, 8-11
b. To clarify if, although the diagnostic sensitivity and specificity of the discriminatory tests can not be assumed to be perfect, the absence of statistically sufficient data on the performance of the tests is not compensated by the procedure in place including a ring trial with additional molecular testing methods in different laboratories and an evaluation by an expert panel chaired by the Community Reference Laboratory for TSEs and taken into account the conclusion of the BIOHAZ Panel in its opinion dated 13 July 2006 that the proportion of sheep being infected by BSE is likely to be extremely small. In page 7 of the Opinion, it is stated that based in the EFSA Opinion of 25 January 2007 on Quantitative Risk Assessment on the residual BSE risk in sheep meat and meat products (EFSA-Q-2005-235, The EFSA Journal, 442, 1-44),
• “[…] the BIOHAZ Panel accepted that the sensitivity and specificity of the discriminatory tests had, for logistical reasons, not been experimentally evaluated and potential confounding factors, such as concomitant infection of the same animal with Scrapie and BSE, remained to be investigated.”
By definition the term diagnostic specificity means the number of correctly identified negative samples divided by the sum of the correctly identified negative and of the false positive samples. If it is uncertain to some degree whether the samples which are negative (this is non-BSE) in the discriminatory tests are correctly identified, an enlargement of the sample size does not add to the already existing data on their real diagnostic specificity.
By definition the term diagnostic sensitivity means the number of correctly identified positive samples divided by the sum of the correctly identified positive and of the false negative samples. Therefore, it is clear that in this case any increase of the number of negative samples is completely irrelevant for the determination of the diagnostic sensitivity of an assay.
To date, the discriminatory tests as described in Regulation (EC) 999/2001, Annex X, Chapter C, point 3.2 (c) have been only validated in the framework of a ring trial employing TSE agents isolated from sheep experimentally infected with Classical BSE agent. No confirmed ovine BSE field case has been detected through this process. Moreover, the tests have not been validated against a possible Classical BSE/other TSE agent co-infection.
In conclusion and also considering the content of the answer to ToR 3.a, the answer to ToR 3.b is:
• Despite consistent performance in ring trials employing samples from experimental ovine BSE cases, there is uncertainty on their performance in the field (because of the lack of detection of natural BSE in ovine or caprine animal).
• TSE positive cases go through the full discriminatory process (including bioassay) only when biochemical discriminatory testing is compatible with BSE signature. Therefore, data obtained through this process can not be used for the evaluation of the sensitivity or the specificity of the discriminatory tests.
The EFSA Journal (2008) 626, 9-11
• Increasing the number of negative results during the TSE discriminatory testing of ovine or caprine animals can not compensate for the absence of statistically sufficient data on the performance of the tests.
The EFSA Journal (2008) 626, 10-11
REFERENCES
Baker, H. F., Ridley, R. M., Wells, G. A. and Ironside, J. W. 1988. Prion protein immunohistochemical staining in the brains of monkeys with transmissible spongiform encephalopathy. Neuropathol. Appl. Neurobiol. 24 (6): 476-86.
Baron, T. G. M. and Biacabe, A. G. 2001. Molecular analysis of the abnormal prion protein during coinfection of mice by bovine spongiform encephalopathy and a Scrapie agent. Journal Of Virology 75 (1): 107-114.
Baron, T., Biacabe, A. G., Arsac, J. N., Benestad, S. and Groschup, M. H. 2007. Atypical transmissible spongiform encephalopathies (TSEs) in ruminants. Vaccine 25 (30): 5625-5630.
Bartz, J. C., Kramer, M. L., Sheehan, M. H., Hutter, J. A. L., Ayers, J. I., Bessen, R. A. and Kincaid, A. E. 2007. Prion interference is due to a reduction in strain-specific PrPSc levels. Journal Of Virology 81 (2): 689-697.
Benestad, S. L., Sarradin, P., Thu, B., Schonheit, J., Tranulis, M. A. and Bratberg, B. 2003. Cases of Scrapie with unusual features in Norway and designation of a new type, Nor98. Veterinary Record 153 (7): 202-+.
Benestad, S. L., Arsac, J. N., Goldmann, W. and Nöremark, M. 2008.Atypical-Nor98 Scrapie: properties of the agent, genetics, and epidemiology. Veterinary Research, 39:19. DOI: 10.1051- vetres:2007056.
http://www.vetres.org/index.php?option=article&access=standard&Itemid=129&url=/articles/vetres/abs/2008/04/v08025/v08025.html
Beringue, V., Andreoletti, O., Le Dur, A., Essalmani, R., Vilotte, J. L., Lacroux, C., Reine, F., Herzog, L., Biacabe, A. G., Baron, T., Caramelli, M., Casalone, C. and Laude, H. 2007. A bovine prion acquires an epidemic bovine spongiform encephalopathy strain-like phenotype on interspecies transmission. Journal Of Neuroscience 27: 6965-6971.
Biacabe, A. G., Laplanche, J. L., Ryder, S. and Baron, T. 2004. Distinct molecular phenotypes in bovine prion diseases. Embo Reports 5 (1): 110-114.
Bruce, ME, Boyle, A, Cousens, S, McConnell, I, Foster, J, Goldmann, W and Fraser, H, 2002. Strain characterization of natural sheep Scrapie and comparison with BSE. Journal of General Virology, 83 (3): 695-704
Buschmann, A., Biacabe, A. G., Ziegler, U., Bencsik, A., Madec, J. Y., Erhardt, G., Luhken, G., Baron, T. and Groschup, M. H. 2004. Atypical Scrapie cases in Germany and France are identified by discrepant reaction patterns in BSE rapid tests. Journal Of Virological Methods 117 (1): 27-36.
Casalone, C., Zanusso, G., Acutis, P., Ferrari, S., Capucci, L., Tagliavini, F., Monaco, S. and Caramelli, M. 2004. Identification of a second bovine amyloidotic spongiform encephalopathy: Molecular similarities with sporadic Creutzfeldt-Jakob disease. Proceedings Of The National Academy Of Sciences Of The United States Of America 101 (9): 3065-3070. EC 2000. Communication from the Commission on the precautionary principle. COMM (2000)
1. http://ec.europa.eu/dgs/health_consumer/library/pub/pub07_en.pdf
EFSA 2005. Opinion of the Scientific Panel on Biological Hazards on the request from the European Commission on classification of Atypical Transmissible Spongiform Encephalopathy (TSE) cases in small ruminants. The EFSA Journal 276: 1-30.
http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753812_1178620776235.htm
The EFSA Journal (2008) 626, 11-11
EFSA 2007. Opinion of the Scientific Panel on Biological Hazards on a request from the European Commission on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals. The EFSA Journal 466: 1-10.
http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753812_1178620775196.htm
Gavier-Widen, D., Noremark, M., Benestad, S., Simmons, M., Renstrom, L., Bratberg, B., Elvander, M. and af Segerstad, C. H. 2004. Recognition of the Nor98 variant of Scrapie in the Swedish sheep population. Journal Of Veterinary Diagnostic Investigation 16 (6): 562-567.
Gibbs, C. J., Amyx, H. L., Bacote, A., Masters, C. L. and Gajdusek, D. C. 1980. Oral- Transmission Of Kuru, Creutzfeldt-Jakob Disease, And Scrapie To Nonhuman-Primates. Journal Of Infectious Diseases 142 (2): 205-208.
Gibbs, C. J. J. and Gajdusek, D. C. 1972. Transmission of Scrapie to the cynomolgus monkey (Macaca fascicularis). Nature 236 (5341): 73-4.
Manuelidis, L. and Lu, Z. Y. 2003. Virus-like interference in the latency and prevention of Creutzfeldt-Jakob disease. Proceedings Of The National Academy Of Sciences Of The United States Of America 100 (9): 5360-5365.
Nishida, N., Katamine, S. and Manuelidis, L. 2005. Reciprocal interference between specific CJD and Scrapie agents in neural cell cultures. Science 310 (5747): 493-496.
Pattison, I.H. and Millson, G.C., 1961.Further experimental observations on Scrapie. Journal of Comparative Pathology. 71:350-9.
Raymond, G. J., Hope, J., Kocisko, D. A., Priola, S. A., Raymond, L. D., Bossers, A., Ironside, J., Will, R. G., Chen, S. G., Petersen, R. B., Gambetti, P., Rubenstein, R., Smits, M. A., Lansbury, P. T. and Caughey, B. 1997. Molecular assessment of the potential transmissibilities of BSE and Scrapie to humans. Nature 388 (6639): 285-288.
Saegerman, C., Vanopdenbosch, E. and Berkvens, D. 2007. Current status of Scrapie. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2 (027): 20 pp.
Stack, M., Jeffrey, M., Deslys, J.P., Grassi, J., Baron, T., Safar, J., Groschup, M., Agrimi, U., Langeveld, J., Matthews, D., Hope, J. and Bostock, C., 2008. An evaluation of techniques for the discrimination of natural scrapie and experimental bovine spongiform encephalopathy in sheep. Document available at the Community Reference Laboratory for Transmissible Spongiform Encephalopathies.
http://www.defra.gov.uk/corporate/vla/science/documents/science-tse-rl-ringtrial.pdf
PLEASE READ ;
7 February 2008 - A Statement on the potential human health risk from changes to classical scrapie controls(41 KB) has been published.
http://www.seac.gov.uk/statements/scrapiestatement080207.pdf
16. There is no firm evidence for a link between human TSEs and classical scrapie. Although a link cannot be ruled out, even if there is a link, the human health risk from classical scrapie must be very low and result in very few human TSE cases per annum. This is because the incidence of human TSEs is very low and relatively constant world-wide (around one case per million people per year) showing that there must be at least a substantial, if not complete, barrier to transmission of classical scrapie to humans. Although it is not possible to quantify any increase in risk that would arise from the changes to classical scrapie controls, the increased risk is
6 © SEAC 2008
highly unlikely to be greater than the risk before classical scrapie controls were introduced. Indeed, given the apparent effect of the National Scrapie Plan (NSP) on reducing the incidence of classical scrapie in the UK, the risk, if it exists, is likely to be appreciably lower than prior to the implementation of the NSP controls. 17. It is possible that the changes to the EU controls may increase the level of atypical scrapie entering the food chain from classical scrapie affected flocks with concurrent atypical scrapie infections. However, given the low occurrence of atypical scrapie within flocks, any increase in the potential human health risk from atypical scrapie is likely to be very low.
Summary
18. Although the changes to the classical scrapie controls may increase the potential risks to human health from small ruminant TSEs, any risk that is present is currently very low or negligible and any increased risk likely to be very low or negligible. For classical scrapie, any increase in potential risk will be less than the longterm historic risk prior to the introduction of small ruminant TSE controls. A risk-benefit analysis is required to determine the proportionality of the changes in controls with respect to the increased potential risks. Such an analysis is not within the remit of SEAC.
SEAC February 2008
http://www.seac.gov.uk/statements/scrapiestatement080207.pdf
Thursday, January 31, 2008
SPONGIFORM ENCEPHALOPATHY ADVISORY COMMITTEE Draft minutes of the 99th meeting held on 14th December 2007
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 ............
snip... please see full text, sources, and comments here ;
http://seac992007.blogspot.com/2008/01/spongiform-encephalopathy-advisory.html
USA MAD COW CASES IN ALABAMA AND TEXAS
***PLEASE NOTE***
USA BASE CASE, (ATYPICAL BSE), AND OR TSE (whatever they are calling it today), please note that both the ALABAMA COW, AND THE TEXAS COW, both were ''H-TYPE'', personal communication Detwiler et al Wednesday, August 22, 2007 11:52 PM. ...TSS
http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0708&L=sanet-mg&T=0&P=19779
P02.35 Molecular Features of the Protease-resistant Prion Protein (PrPres) in H- type BSE
Biacabe, A-G1; Jacobs, JG2; Gavier-Widén, D3; Vulin, J1; Langeveld, JPM2; Baron, TGM1 1AFSSA, France; 2CIDC-Lelystad, Netherlands; 3SVA, Sweden
Western blot analyses of PrPres accumulating in the brain of BSE- infected cattle have demonstrated 3 different molecular phenotypes regarding to the apparent molecular masses and glycoform ratios of PrPres bands. We initially described isolates (H-type BSE) essentially characterized by higher PrPres molecular mass and decreased levels of the diglycosylated PrPres band, in contrast to the classical type of BSE. This type is also distinct from another BSE phenotype named L-type BSE, or also BASE (for Bovine Amyloid Spongiform Encephalopathy), mainly characterized by a low representation of the diglycosylated PrPres band as well as a lower PrPres molecular mass. Retrospective molecular studies in France of all available BSE cases older than 8 years old and of part of the other cases identified since the beginning of the exhaustive surveillance of the disease in 20001 allowed to identify 7 H- type BSE cases, among 594 BSE cases that could be classified as classical, L- or H-type BSE. By Western blot analysis of H-type PrPres, we described a remarkable specific feature with antibodies raised against the C-terminal region of PrP that demonstrated the existence of a more C-terminal cleaved form of PrPres (named PrPres#2 ), in addition to the usual PrPres form (PrPres #1). In the unglycosylated form, PrPres #2 migrates at about 14 kDa, compared to 20 kDa for PrPres #1. The proportion of the PrPres#2 in cattle seems to by higher compared to the PrPres#1. Furthermore another PK–resistant fragment at about 7 kDa was detected by some more N-terminal antibodies and presumed to be the result of cleavages of both N- and C- terminal parts of PrP. These singular features were maintained after transmission of the disease to C57Bl/6 mice. The identification of these two additional PrPres fragments (PrPres #2 and 7kDa band) *** reminds features reported respectively in sporadic Creutzfeldt-Jakob disease and in Gerstmann-Sträussler-Scheinker (GSS) syndrome in humans.
FC5.5.1 BASE Transmitted to Primates and MV2 sCJD Subtype Share PrP27-30 and PrPSc C-terminal Truncated Fragments
Zanusso, G1; Commoy, E2; Fasoli, E3; Fiorini, M3; Lescoutra, N4; Ruchoux, MM4; Casalone, C5; Caramelli, M5; Ferrari, S3; Lasmezas, C6; Deslys, J-P4; Monaco, S3 1University of Verona, of Neurological and Visual Sciences, Italy; 2CEA, IMETI/SEPIA, France; 3University of Verona, Neurological and Visual Sciences, Italy; 4IMETI/SEPIA, France; 5IZSPLVA, Italy; 6The Scripps Research Insitute, USA
The etiology of sporadic Creutzfeldt-Jakob disease (sCJD), the most frequent human prion disease, remains still unknown. The marked disease phenotype heterogeneity observed in sCJD is thought to be influenced by the type of proteinase K- resistant prion protein, or PrPSc (type 1 or type 2 according to the electrophoretic mobility of the unglycosylated backbone), and by the host polymorphic Methionine/Valine (M/V) codon 129 of the PRNP. By using a two-dimensional gel electrophoresis (2D-PAGE) and imunoblotting we previously showed that in sCJD, in addition to the PrPSc type, distinct PrPSc C-terminal truncated fragments (CTFs) correlated with different sCJD subtypes. Based on the combination of CTFs and PrPSc type, we distinguished three PrPSc patterns: (i) the first was observed in sCJD with PrPSc type 1 of all genotypes,;
(ii) the second was found in M/M-2 (cortical form); (iii) the third in amyloidogenic M/V- 2 and V/V-2 subtypes (Zanusso et al., JBC 2004) . Recently, we showed that sCJD subtype M/V-2 shared molecular and pathological features with an atypical form of BSE, named BASE, thus suggesting a potential link between the two conditions. This connection was further confirmed after 2D-PAGE analysis, which showed an identical PrPSc signature, including the biochemical pattern of CTFs. To pursue this issue, we obtained brain homogenates from Cynomolgus macaques intracerebrally inoculated with brain homogenates from BASE. Samples were separated by using a twodimensional electrophoresis (2D-PAGE) followed by immunoblotting. We here show that the PrPSc pattern obtained in infected primates is identical to BASE and sCJD MV-2 subtype. *** These data strongly support the link, or at least a common ancestry, between a sCJD subtype and BASE. This work was supported by Neuroprion (FOOD-CT-2004-506579)
FC5.5.2 Transmission of Italian BSE and BASE Isolates in Cattle Results into a Typical BSE Phenotype and a Muscle Wasting Disease
Zanusso, G1; Lombardi, G2; Casalone, C3; D’Angelo, A4; Gelmetti, D2; Torcoli, G2; Barbieri, I2; Corona, C3; Fasoli, E1; Farinazzo, A1; Fiorini, M1; Gelati, M1; Iulini, B3; Tagliavini, F5; Ferrari, S1; Monaco, S1; Caramelli, M3; Capucci, L2 1University of Verona, Neurological and Visual Sciences, Italy; 2IZSLER, Italy; 3IZSPLVA, Italy; 4University of Turin, Animal Pathology, Italy; 5Isituto Carlo Besta, Italy
The clinical phenotype of bovine spongiform encephalopathy has been extensively reported in early accounts of the disorder. Following the introduction of statutory active surveillance, almost all BSE cases have been diagnosed on a pathological/molecular basis, in a pre-symptomatic clinical stage. In recent years, the active surveillance system has uncovered atypical BSE cases, which are characterized by distinct conformers of the PrPSc, named high-type (BSE-H) and low-type (BSE-L), whose clinicopathological phenotypes remain unknown. We recently reported two Italian atypical cases with a PrPSc type similar to BSE-L, pathologically characterized by PrP amyloid plaques. Experimental transmission to TgBov mice has recently disclosed that BASE is caused by a distinct prion strain which is extremely virulent. A major limitation of transmission studies to mice is the lack of reliable information on clinical phenotype of BASE in its natural host. In the present study, we experimentally infected Fresian/Holstein and Alpine/Brown cattle with Italian BSE and BASE isolates by i.c. route. BASE infected cattle showed survival times significantly shorter than BSE, a finding more readily evident in Fresian/Holstein, and in keeping with previous observations in TgBov mice. Clinically, BSE-infected cattle developed a disease phenotype highly comparable with that described in field BSE cases and in experimentally challenged cattle. On the contrary, BASE-inoculated cattle developed an amyotrophic disorder accompanied by mental dullness. The molecular and neuropathological profiles, including PrP deposition pattern, closely matched those observed in the original cases. This study further confirms that BASE is caused by a distinct prion isolate and discloses a novel disease phenotype in cattle, closely resembling the phenotype previous reported in scrapie-inoculated cattle *** and in some subtypes of inherited and sporadic Creutzfeldt-Jakob disease. Oral Abstracts 14
P04.27
Experimental BSE Infection of Non-human Primates: Efficacy of the Oral Route
Holznagel, E1; Yutzy, B1; Deslys, J-P2; Lasmézas, C2; Pocchiari, M3; Ingrosso, L3; Bierke, P4; Schulz-Schaeffer, W5; Motzkus, D6; Hunsmann, G6; Löwer, J1 1Paul-Ehrlich-Institut, Germany; 2Commissariat à l´Energie Atomique, France; 3Instituto Superiore di Sanità, Italy; 4Swedish Institute for Infectious Disease control, Sweden; 5Georg August University, Germany; 6German Primate Center, Germany
Background:
In 2001, a study was initiated in primates to assess the risk for humans to contract BSE through contaminated food. For this purpose, BSE brain was titrated in cynomolgus monkeys.
Aims:
The primary objective is the determination of the minimal infectious dose (MID50) for oral exposure to BSE in a simian model, and, by in doing this, to assess the risk for humans. Secondly, we aimed at examining the course of the disease to identify possible biomarkers.
Methods:
Groups with six monkeys each were orally dosed with lowering amounts of BSE brain: 16g, 5g, 0.5g, 0.05g, and 0.005g. In a second titration study, animals were intracerebrally (i.c.) dosed (50, 5, 0.5, 0.05, and 0.005 mg).
Results:
In an ongoing study, a considerable number of high-dosed macaques already developed simian vCJD upon oral or intracerebral exposure or are at the onset of the clinical phase. However, there are differences in the clinical course between orally and intracerebrally infected animals that may influence the detection of biomarkers.
Conclusions:
Simian vCJD can be easily triggered in cynomolgus monkeys on the oral route using less than 5 g BSE brain homogenate. The difference in the incubation period between 5 g oral and 5 mg i.c. is only 1 year (5 years versus 4 years). However, there are rapid progressors among orally dosed monkeys that develop simian v CJD as fast as intracerebrally inoculated animals.
The work referenced was performed in partial fulfilment of the study “BSE in primates“ supported by the EU (QLK1-2002-01096).
Subject: Aspects of the Cerebellar Neuropathology in Nor98
Date: September 26, 2007 at 4:06 pm PST
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
IS THERE A SCRAPIE-LIKE DISEASE IN CATTLE ?
In April of 1985, a mink rancher in Wisconsin reported a debilitating neurologic disease in his herd which we diagnosed as TME by histopathologic findings confirmed by experimental transmission to mink and squirrel monkeys. The rancher was a ''dead stock'' feeder using mostly (>95%) downer or dead dairy cattle and a few horses. She had never been fed.
We believe that these findings may indicate the presence of a previously unrecognized scrapie-like disease in cattle and wish to alert dairy practitioners to this possibility.
snip...
PROCEEDINGS OF THE SEVENTH ANNUAL WESTERN CONFERENCE FOR FOOD ANIMAL VETERINARY MEDICINE, University of Arizona, March 17-19, 1986
http://www.bseinquiry.gov.uk/files/mb/m09a/tab01.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
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
Epidemiology of Scrapie in the United States 1977
http://www.bseinquiry.gov.uk/files/mb/m08b/tab64.pdf
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
Like lambs to the slaughter
31 March 2001 Debora MacKenzie Magazine issue 2284
FOUR years ago, Terry Singeltary watched his mother die horribly from a degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.
Most doctors believe that sCJD is caused by a prion protein deforming by chance into a killer. But Singeltary thinks otherwise. He is one of a number of campaigners who say that some sCJD, like the variant CJD related to BSE, is caused by eating meat from infected animals. Their suspicions have focused on sheep carrying scrapie, a BSE-like disease that is widespread in flocks across Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight to the campaigners' fears. To their complete surprise, the researchers found that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by some strains of scrapie," says team member Jean-Philippe Deslys of the French Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses, south-west of Paris.
Hans Kretschmar of the University of Göttingen, who coordinates CJD surveillance in Germany, is so concerned by the findings that he now wants to trawl back through past sCJD cases to see if any might have been caused by eating infected mutton or lamb. ...
http://www.newscientist.com/article/mg16922840.300-like-lambs-to-the-slaughter.html
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 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 intracerebral route? Are some VRQ sheep carriers with no neurological symptoms?
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
http://nor-98.blogspot.com/
SCRAPIE USA
http://scrapie-usa.blogspot.com/
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Singeltary, Sr et al. JAMA.2001; 285: 733-734.
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.
To the Editor: In their Research Letter, Dr Gibbons and colleagues1 reported that the annual US death rate due to Creutzfeldt-Jakob disease (CJD) has been stable since 1985. These estimates, however, are based only on reported cases, and do not include misdiagnosed or preclinical cases. It seems to me that misdiagnosis alone would drastically change these figures. An unknown number of persons with a diagnosis of Alzheimer disease in fact may have CJD, although only a small number of these patients receive the postmortem examination necessary to make this diagnosis. Furthermore, only a few states have made CJD reportable. Human and animal transmissible spongiform encephalopathies should be reportable nationwide and internationally.
Terry S. Singeltary, Sr Bacliff, Tex
1. Gibbons RV, Holman RC, Belay ED, Schonberger LB. Creutzfeldt-Jakob disease in the United States: 1979-1998. JAMA. 2000;284:2322-2323. FREE FULL TEXT
http://jama.ama-assn.org/cgi/content/extract/285/6/733?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=singeltary&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
APHIS-2006-0041-0006 TSE advisory committee for the meeting December 15, 2006
http://www.regulations.gov/fdmspublic/ContentViewer?objectId=09000064801f3413&disposition=attachment&contentType=msw8
[Docket No. FSIS-2006-0011] FSIS Harvard Risk Assessment of Bovine Spongiform Encephalopathy (BSE)
http://www.fsis.usda.gov/OPPDE/Comments/2006-0011/2006-0011-1.pdf
[Docket No. 03-025IFA] FSIS Prohibition of the Use of Specified Risk Materials for Human Food and Requirement for the Disposition of Non-Ambulatory Disabled Cattle
http://www.fsis.usda.gov/OPPDE/Comments/03-025IFA/03-025IFA-2.pdf
Attachment to Singeltary comment
January 28, 2007
Greetings APHIS,
I would kindly like to submit the following to ;
BSE; MRR; IMPORTATION OF LIVE BOVINES AND PRODUCTS DERIVED FROM BOVINES [Docket No. APHIS-2006-0041] RIN 0579-AC01
[Federal Register: January 9, 2007 (Volume 72, Number 5)] [Proposed Rules] [Page 1101-1129] From the Federal Register Online via GPO Access [wais.access.gpo.gov] [DOCID:fr09ja07-21]
http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetail&o=09000064801f8152
BSE; MRR; IMPORTATION OF LIVE BOVINES AND PRODUCTS DERIVED FROM BOVINES [Docket No. APHIS-2006-0041] RIN 0579-AC01 Date: January 9, 2007 at 9:08 am PST
http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetail&o=09000064801f3412
USDA CERTIFIED H-BASE MAD COW SCHOOL LUNCH PROGRAM
http://cjdmadcowbaseoct2007.blogspot.com/2008/02/usda-certified-h-base-mad-cow-school.html
Terry S. Singeltary Sr. P.O. Box 42 Bacliff, Texas USA 77518
The EFSA Journal (2008) 626, 1-11
© European Food Safety Authority, 2008
Scientific and technical clarification in the interpretation and consideration of some facets of the conclusions of its Opinion of 8 March 2007 on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals1
Scientific Report of the Scientific Panel on Biological Hazards
January 2008 - 37th Plenary meeting
Question EFSA-Q-2007-193
PANEL MEMBERS
Olivier Andreoletti, Herbert Budka, Sava Buncic, Pierre Colin, John D Collins, Aline De Koeijer, John Griffin, Arie Havelaar, James Hope, Günter Klein, Hilde Kruse, Simone Magnino, Antonio Martínez López, James McLauchlin, Christophe Nguyen-The, Karsten Noeckler, Birgit Noerrung, Miguel Prieto Maradona, Terence Roberts, Ivar Vågsholm, Emmanuel Vanopdenbosch.
ACKNOWLEDGEMENTS
The European Food Safety Authority wishes to thank the members of the Working Group for their contribution to this Scientific and Technical clarification: Olivier Andreoletti, Herbert Budka, Martin Groschup, James Hope, Danny Matthews, Marion Simmons, Emmanuel Vanopdenbosch (Chairman) and Kathy Webster.
1 For citation purposes: Scientific Report of the Panel on Biological Hazards on a request from the European Commission on “Scientific and technical clarification in the interpretation and consideration of some facets of the conclusions of its Opinion of 8 March 2007 on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals”. The EFSA Journal (2008), 626, 1-11. The EFSA Journal (2008) 626, 2-11
INTRODUCTORY STATEMENT FROM THE MEMBERS OF THE PANEL ON BIOLOGICAL HAZARDS ON COMMUNICATING SCIENTIFIC UNCERTAINTY
Scientific uncertainty results usually from five characteristics of the scientific method (EC, 2000): the variable chosen, the measurements made, the samples drawn, the models used and the causal relationship employed. This may also arise from a controversy on existing data or lack of some relevant data. Following appropriate scientific risk assessment, the expression of such uncertainty in complex settings, by simple and concise wording without sacrificing scientific exactness, is one of the major challenges of risk communication.
The following report is strictly limited to replying to the terms of reference as received from the European Commission by re-addressing the uncertainties that were reflected in the conclusions of the concerned EFSA 2007 opinion.
ANSWERS TO THE TERMS OF REFERENCE
1. In relation to conclusion 2 in page 7 the Authority is invited to clarify and substantiate if there is at this stage any scientific evidence about the presence of TSEs agents other than BSE, Classical and Atypical Scrapie agents in ovine or caprine animals.
Conclusion 2 in page 7 of the EFSA 2007 opinion states that: “The BSE agent is the only TSE agent identified as zoonotic. However, in view of their diversity it is currently not possible to exclude transmissibility to humans of other animal TSE agents.”
In the preamble of the EFSA 2007 opinion it is stated that:
• “Any positive case of TSE in small ruminants is termed as “TSE in small ruminants” which encompasses Classical Scrapie, Atypical Scrapie including Nor98 in sheep and goats as well as BSE in these species if found.”
It should be noted that, under 3.2.1 of the EFSA 2007 opinion it is stated that:
• “The introduction of active surveillance programmes in the European Union has led to the recognition of isolates that do not conform to previous phenotypes of BSE in cattle and Classical Scrapie in sheep. These are currently termed for operational reasons as “Atypical” BSE or Scrapie, but probably reflect part of a wider spectrum of isolates not previously recognised, and in the case of Atypical Scrapie affecting genotypes highly resistant to clinical Scrapie (Biacabe et al., 2004; Casalone et al., 2004; Benestad et al., 2003; Gavier- Widen et al., 2004; Buschmann et al., 2004).” Scrapie is a disease of ovine and caprine animals caused by a variety of TSE agents harbouring different biological properties that are still incompletely characterised, rather than by one specific transmissible entity. ‘Classical Scrapie’ and ‘Atypical Scrapie’ are operational rather than purely biological terms. (EFSA, 2005; Saegerman et al., 2007;
Benestad et al., 2008). The EFSA Journal (2008) 626, 3-11
Further on the EFSA 2007 opinion, under 3.2.3 the Panel acknowledges that there is a:
• “[…] lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents […]”
This is in accordance to the approach taken by the Panel in the EFSA 2005 opinion when classifying the possible TSE cases in small ruminants. In fact, the EFSA 2007 opinion stresses that:
• “Practical definitions of TSE in small ruminants are summarized in the EFSA opinion on the classification of Atypical and Classical Scrapie and BSE in small ruminants (EFSA, 2005) in the Table “Criteria for the categorisation of TSEs in small ruminants” (in annex 1 of the said EFSA opinion).”
In Annex 1 of the EFSA 2005 opinion, a table for the categorisation of TSEs in small ruminants can be found. This opinion concludes that the definition of Atypical Scrapie:
• “[…] is provided in juxtaposition with similar definitions for Scrapie and BSE in small ruminants. Sub-categorisation of Scrapie and Atypical Scrapie is premature although this may become possible when more data are available.” Recent studies have identified TSE agents in cattle that differ from the original TSE agent type, which causes the disease commonly known as BSE that was detected since 1986 in the United Kingdom and is referred to as ‘Classical BSE’ in this document.
Based on their diagnostic phenotypes these more recently identified TSE agents in cattle are called L- and H-type BSE agents (Biacabe et al., 2004; Casalone et al., 2004; Baron et al., 2007). In conclusion, the reply to the ToR number 1 is:
• In ovine animals, no TSE agents other than those causing Classical Scrapie and Atypical Scrapie have been identified.
• In caprine animals, no TSE agents other than those causing BSE, Classical Scrapie and Atypical Scrapie have been identified.
• The operational term ‘BSE’ covers a TSE of bovine animals that could be caused by at least three distinct TSE agents with heterogeneous biological properties.
• The operational term ‘Classical Scrapie’ covers a TSE of ovine and caprine animals caused by several TSE agents with heterogeneous biological properties.
• The operational term ‘Atypical Scrapie’ covers a TSE of ovine and caprine animals that differs from Classical Scrapie. Currently, it is a subject for debate whether it is caused by one or more TSE agents. The EFSA Journal (2008) 626, 4-11
2. In relation to conclusion 2 in page 7 the Authority is invited to specify the scientific evidences which do not allow to exclude transmissibility to humans of “other TSE agents” other than BSE. Conclusion 2 in page 7 of the EFSA 2007 opinion states that: “The BSE agent is the only TSE agent identified as zoonotic. However, in view of their diversity it is currently not possible to exclude transmissibility to humans of other animal TSE agents.”
In the EFSA 2007 opinion under 3.2.3. the Panel states that:
• “There are significant uncertainties associated with the question whether TSE agents in their whole spectrum may cross the human transmission barrier under natural conditions”.
This statement is supported both by scientific evidence and considerations, referenced in the EFSA 2007 opinion:
• Scientific evidence from transmission studies to primates: - Transmission of Classical Scrapie from a TSE agent adapted in hamster was demonstrated by oral challenge in squirrel monkey (Saimiri sciureus) (Gibbs et al., 1980);
- Transmission of Classical Scrapie from two distinct sheep sources by intracerebral challenge in cynomologus monkey (Macaca fascicularis) and marmoset monkey (Callithrix jacchus) (Gibbs and Gajdusek, 1972; Baker et al., 1988).
• Scientific considerations on TSE epidemiology: - “The assumed lack of association between TSEs in humans and those in small ruminants […] may be biased by a number of factors: (i) The lack of a data on the historical real prevalence and distribution of small ruminant TSEs, at a time where only passive surveillance was performed; (ii) the lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents; (iii) the lack of understanding of the diversity of TSEs in humans due to the limited molecular and bioassay characterisation of human TSEs also in relation to the number and spectrum of neurodegenerative diseases of humans; (iv) the predicted phenotype of disease that might arise should an animal derived TSE transmit to humans.” The EFSA Journal (2008) 626, 5-11
Further evidence is provided by:
• In vitro conversion assays: Raymond et al. (1997) studied whether there is a correlation between in vitro conversion efficiencies and known transmissibility of BSE, sheep Scrapie and CJD, and found limited conversion of human PrP-sen to PrP-res driven by PrP-res associated with both Scrapie (PrPSc) and BSE (PrPBSE). They concluded that “the inherent ability of these infectious agents of BSE and Scrapie to affect humans following equivalent exposure may be finite but similarly low”. Nevertheless, uncertainty arises from the fact that this is a simple in vitro model of a complex in vivo situation.
• Laboratory transmission studies with animal models: Since the publication of the Opinion new data have become available with regards to L type of BSE, which has now been identified in various EU members states (Biacabe et al., 2004; Casalone et al., 2004; Baron et al., 2007). This TSE agent, differing from that causing Classical BSE by its biochemical signature and transmission features in mouse models, has been transmitted to a Tg mouse model expressing Human M129 PRP gene (Beringue et al. 2007)2. Here again, uncertainty arises from the limitations of these animal models for the estimation of the human species barrier. These ‘proof of principle’ experiments provide data supporting the ability of TSE agents other than those causing Classical BSE to cross the human species barrier.
Even so, it is important to remember that as mentioned in the EFSA 2007 opinion, transmission to primates:
• “… does not allow to take into account the human gene PRNP polymorphisms (in particular the M/V 129), that have been identified to play a major role on relative susceptibility towards prion disease. In addition, genes other than the PrP gene may also be influential in determining overall susceptibility to TSEs.” Despite the interests in the area, studies of the transmissibility of currently known TSE agents using animal models will remain incomplete for several years.
In conclusion, the reply to the ToR number 2 is:
• Experimental transmissions to primate and to transgenic (Tg) mouse models expressing the human PrP gene, are currently used as to evaluate the potential capacity of a TSE agent to cross the human species barrier.
• TSE agents other than the Classical BSE agent from three field TSE cases (two Classical Scrapie cases and one L type BSE case) have been demonstrated to cross the modelled human species barrier.
• Some limitations to these models have to be considered, which include:
(i) The uncertainty of how well they represent the human species barrier. (ii) The uncertainty of how well the experimental inoculation route employed represents exposure under natural conditions. 2 Transmission of this TSE agent by intracerebral challenge to primates (Macaques) has been reported by Comoy et al. at the 2006 Prion Congress held in Torino. A scientific paper reporting this finding has been submitted for peer review publication. The EFSA Journal (2008) 626, 6-11
3. In relation to conclusion 3 in page 7, the Authority is invited:
a. To clarify if, although the diagnostic sensitivity and specificity of the discriminatory tests can not be assumed to be perfect, they are at this moment the diagnostic tool fit for the differentiation of the different TSE strains which can be present in ovine and caprine animals if they are performed according to the procedure described in point 3.2 (c) of Chapter C of Annex X to Regulation (EC) 999/2001.
Clarification of the ToR 3.a.: During the discussion of the WG it was clarified with the Commission services that when referring to differentiation of different TSE strains it was meant “identification of the TSE agent that causes Classical BSE versus any other TSE agent that can be present in ovine or caprine animals”.
Conclusion 3 in page 7 of the EFSA 2007 opinion states that:
• “Current discriminatory tests as described in the EC legislation to be used for discrimination between Scrapie and BSE appear, up to now, to be reliable for the differentiation of BSE from Classical and Atypical Scrapie. However, at the current stage of scientific knowledge, neither their diagnostic sensitivity nor their specificity can be assumed to be perfect.” Characterisation of TSE agents is based on biological and/or molecular methods. Molecular methods are based on the properties of the disease-specific proteaseresistant fragments of PrPSc or physico-chemical behaviour (e.g. proteinase K cleavage site, PrPSc glycosylation, relative proteinase K resistance, molecular conformation, etc). Biological methods identify the reproducibility and stability of the disease phenotype, including lesion profile and incubation period, on serial transmission in a specified mouse line, but also consider the phenotype of the disease in the host species. Discriminatory biochemical tests, as referred here, only represent a group of standardised methods (reagent protocols) allowing reproducible identification of certain abnormal PrP biochemical features associated with the TSE agent causing Classical BSE experimentally propagated in sheep. These biochemical methods cannot be considered to be appropriate tools for the differentiation of the different TSE agents (excluding the agent that causes Classical BSE), which can be present in ovine and caprine animals in the wider sense, as they have not been designed for that purpose.
In page 7 of the EFSA 2007 opinion, it is stated that based on the EFSA Opinion of 25 January 2007 on Quantitative Risk Assessment on the residual BSE risk in sheep meat and meat products (EFSA-Q-2005-235),
• “The Scrapie/BSE discriminatory tests are robust judging by their performance against a small number of samples in a blinded ring trial organised by the EU TSE Community Reference Laboratory (Stack et al., in preparation) and their application as part of small ruminant surveillance was continuing to improve the accuracy of these prevalence estimates. However, balanced against this optimistic scenario, the BIOHAZ Panel accepted that the sensitivity and specificity of the discriminatory tests had, for logistical reasons, not been experimentally evaluated and potential confounding factors, such as
The EFSA Journal (2008) 626, 7-11
concomitant infection of the same animal with Scrapie and BSE, remained to be investigated.” The result of that ring trial employing a limited number of different categories of samples3shows that all tests were able to discriminate between field cases of Classical Scrapie in sheep and the types of BSE in sheep available from experimental animals (Stack et al., 2008).
Moreover, it should be noted that as previously reported under 3.2.3 of the 2007 EFSA opinion, the Panel acknowledged that there is a:
• “[…]lack of understanding of the true biodiversity of TSEs in small ruminants in terms of both Classical and Atypical agents […]”
In field cases of Classical Scrapie, more than one TSE agent can be isolated from a single animal (Pattison et al., 1961; Bruce, et al., 2002). The presence of one TSE agent can mask the presence of another as well as its manifestation with disease, when co-infecting the same individual. This phenomenon of “interference” has been studied in experimental models using different TSE agents (Manuelidis and Lu, 2003; Nishida et al., 2005; Bartz et al., 2007). Data reported by Baron and Biacabe (2001) indicated that intracerebral inoculation of C57Bl6 mice with a mixture of Scrapie and BSE agents, which were both already adapted to this mouse strain (i.e. species barrier effects had been ablated), resulted in the development of a TSE which presented with a Scrapie Western blot profile. Despite the fact that direct extrapolation of these observations to small ruminants is not possible, these results raise the possibility that the presence of BSE in sheep, if it occurred as a co-infecting TSE agent following established Scrapie, may remain undetected. As the likelihood of such a situation is uncertain at this moment, experiments designed to answer specifically to this question are currently ongoing in an EU funded program (QLK – CT –2001- 01309 BSE in sheep). The Panel recognises the uncertainty of performance of the discriminatory tests applied to small ruminants but also that it is pivotal to have some estimate of the likelihood of co-infection of BSE and Scrapie in the same animal. This would aid the understanding of the practical impact of this uncertainty.
In conclusion, the reply to the ToR number 3.a. is:
• Based on the limited data available, the discriminatory tests as implemented at EU level are practicable tools for screening of field TSE cases (as mentioned in Regulation 999/2001, Annex X, Chapter C, point 3.2. (c)), fulfilling the objective of rapid and reproducible identification of TSE cases that have a signature compatible with Classical BSE agent.
• These discriminatory tests cannot be considered to be perfect because of the current lack of understanding of both the true biodiversity of TSE agents in ovine and caprine animals and how the agents interact in case of co-infection. 3 These were: 4 Ovine BSE samples from ovine oral primary challenge with bovine BSE brain; 10 Ovine BSE samples, from intracerebral challenge with Cheviot AHQ/AHQ ovine BSE (1st sheep to sheep challenge); 12 Sheep Scrapie, positive by statutory tests; 9 Scrapie clinical suspects, negative by statutory tests; 2 Control sheep, negative samples; 2 confirmed bovine BSE positives; 2 Bovine negative controls.
The EFSA Journal (2008) 626, 8-11
b. To clarify if, although the diagnostic sensitivity and specificity of the discriminatory tests can not be assumed to be perfect, the absence of statistically sufficient data on the performance of the tests is not compensated by the procedure in place including a ring trial with additional molecular testing methods in different laboratories and an evaluation by an expert panel chaired by the Community Reference Laboratory for TSEs and taken into account the conclusion of the BIOHAZ Panel in its opinion dated 13 July 2006 that the proportion of sheep being infected by BSE is likely to be extremely small. In page 7 of the Opinion, it is stated that based in the EFSA Opinion of 25 January 2007 on Quantitative Risk Assessment on the residual BSE risk in sheep meat and meat products (EFSA-Q-2005-235, The EFSA Journal, 442, 1-44),
• “[…] the BIOHAZ Panel accepted that the sensitivity and specificity of the discriminatory tests had, for logistical reasons, not been experimentally evaluated and potential confounding factors, such as concomitant infection of the same animal with Scrapie and BSE, remained to be investigated.”
By definition the term diagnostic specificity means the number of correctly identified negative samples divided by the sum of the correctly identified negative and of the false positive samples. If it is uncertain to some degree whether the samples which are negative (this is non-BSE) in the discriminatory tests are correctly identified, an enlargement of the sample size does not add to the already existing data on their real diagnostic specificity.
By definition the term diagnostic sensitivity means the number of correctly identified positive samples divided by the sum of the correctly identified positive and of the false negative samples. Therefore, it is clear that in this case any increase of the number of negative samples is completely irrelevant for the determination of the diagnostic sensitivity of an assay.
To date, the discriminatory tests as described in Regulation (EC) 999/2001, Annex X, Chapter C, point 3.2 (c) have been only validated in the framework of a ring trial employing TSE agents isolated from sheep experimentally infected with Classical BSE agent. No confirmed ovine BSE field case has been detected through this process. Moreover, the tests have not been validated against a possible Classical BSE/other TSE agent co-infection.
In conclusion and also considering the content of the answer to ToR 3.a, the answer to ToR 3.b is:
• Despite consistent performance in ring trials employing samples from experimental ovine BSE cases, there is uncertainty on their performance in the field (because of the lack of detection of natural BSE in ovine or caprine animal).
• TSE positive cases go through the full discriminatory process (including bioassay) only when biochemical discriminatory testing is compatible with BSE signature. Therefore, data obtained through this process can not be used for the evaluation of the sensitivity or the specificity of the discriminatory tests.
The EFSA Journal (2008) 626, 9-11
• Increasing the number of negative results during the TSE discriminatory testing of ovine or caprine animals can not compensate for the absence of statistically sufficient data on the performance of the tests.
The EFSA Journal (2008) 626, 10-11
REFERENCES
Baker, H. F., Ridley, R. M., Wells, G. A. and Ironside, J. W. 1988. Prion protein immunohistochemical staining in the brains of monkeys with transmissible spongiform encephalopathy. Neuropathol. Appl. Neurobiol. 24 (6): 476-86.
Baron, T. G. M. and Biacabe, A. G. 2001. Molecular analysis of the abnormal prion protein during coinfection of mice by bovine spongiform encephalopathy and a Scrapie agent. Journal Of Virology 75 (1): 107-114.
Baron, T., Biacabe, A. G., Arsac, J. N., Benestad, S. and Groschup, M. H. 2007. Atypical transmissible spongiform encephalopathies (TSEs) in ruminants. Vaccine 25 (30): 5625-5630.
Bartz, J. C., Kramer, M. L., Sheehan, M. H., Hutter, J. A. L., Ayers, J. I., Bessen, R. A. and Kincaid, A. E. 2007. Prion interference is due to a reduction in strain-specific PrPSc levels. Journal Of Virology 81 (2): 689-697.
Benestad, S. L., Sarradin, P., Thu, B., Schonheit, J., Tranulis, M. A. and Bratberg, B. 2003. Cases of Scrapie with unusual features in Norway and designation of a new type, Nor98. Veterinary Record 153 (7): 202-+.
Benestad, S. L., Arsac, J. N., Goldmann, W. and Nöremark, M. 2008.Atypical-Nor98 Scrapie: properties of the agent, genetics, and epidemiology. Veterinary Research, 39:19. DOI: 10.1051- vetres:2007056.
http://www.vetres.org/index.php?option=article&access=standard&Itemid=129&url=/articles/vetres/abs/2008/04/v08025/v08025.html
Beringue, V., Andreoletti, O., Le Dur, A., Essalmani, R., Vilotte, J. L., Lacroux, C., Reine, F., Herzog, L., Biacabe, A. G., Baron, T., Caramelli, M., Casalone, C. and Laude, H. 2007. A bovine prion acquires an epidemic bovine spongiform encephalopathy strain-like phenotype on interspecies transmission. Journal Of Neuroscience 27: 6965-6971.
Biacabe, A. G., Laplanche, J. L., Ryder, S. and Baron, T. 2004. Distinct molecular phenotypes in bovine prion diseases. Embo Reports 5 (1): 110-114.
Bruce, ME, Boyle, A, Cousens, S, McConnell, I, Foster, J, Goldmann, W and Fraser, H, 2002. Strain characterization of natural sheep Scrapie and comparison with BSE. Journal of General Virology, 83 (3): 695-704
Buschmann, A., Biacabe, A. G., Ziegler, U., Bencsik, A., Madec, J. Y., Erhardt, G., Luhken, G., Baron, T. and Groschup, M. H. 2004. Atypical Scrapie cases in Germany and France are identified by discrepant reaction patterns in BSE rapid tests. Journal Of Virological Methods 117 (1): 27-36.
Casalone, C., Zanusso, G., Acutis, P., Ferrari, S., Capucci, L., Tagliavini, F., Monaco, S. and Caramelli, M. 2004. Identification of a second bovine amyloidotic spongiform encephalopathy: Molecular similarities with sporadic Creutzfeldt-Jakob disease. Proceedings Of The National Academy Of Sciences Of The United States Of America 101 (9): 3065-3070. EC 2000. Communication from the Commission on the precautionary principle. COMM (2000)
1. http://ec.europa.eu/dgs/health_consumer/library/pub/pub07_en.pdf
EFSA 2005. Opinion of the Scientific Panel on Biological Hazards on the request from the European Commission on classification of Atypical Transmissible Spongiform Encephalopathy (TSE) cases in small ruminants. The EFSA Journal 276: 1-30.
http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753812_1178620776235.htm
The EFSA Journal (2008) 626, 11-11
EFSA 2007. Opinion of the Scientific Panel on Biological Hazards on a request from the European Commission on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals. The EFSA Journal 466: 1-10.
http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753812_1178620775196.htm
Gavier-Widen, D., Noremark, M., Benestad, S., Simmons, M., Renstrom, L., Bratberg, B., Elvander, M. and af Segerstad, C. H. 2004. Recognition of the Nor98 variant of Scrapie in the Swedish sheep population. Journal Of Veterinary Diagnostic Investigation 16 (6): 562-567.
Gibbs, C. J., Amyx, H. L., Bacote, A., Masters, C. L. and Gajdusek, D. C. 1980. Oral- Transmission Of Kuru, Creutzfeldt-Jakob Disease, And Scrapie To Nonhuman-Primates. Journal Of Infectious Diseases 142 (2): 205-208.
Gibbs, C. J. J. and Gajdusek, D. C. 1972. Transmission of Scrapie to the cynomolgus monkey (Macaca fascicularis). Nature 236 (5341): 73-4.
Manuelidis, L. and Lu, Z. Y. 2003. Virus-like interference in the latency and prevention of Creutzfeldt-Jakob disease. Proceedings Of The National Academy Of Sciences Of The United States Of America 100 (9): 5360-5365.
Nishida, N., Katamine, S. and Manuelidis, L. 2005. Reciprocal interference between specific CJD and Scrapie agents in neural cell cultures. Science 310 (5747): 493-496.
Pattison, I.H. and Millson, G.C., 1961.Further experimental observations on Scrapie. Journal of Comparative Pathology. 71:350-9.
Raymond, G. J., Hope, J., Kocisko, D. A., Priola, S. A., Raymond, L. D., Bossers, A., Ironside, J., Will, R. G., Chen, S. G., Petersen, R. B., Gambetti, P., Rubenstein, R., Smits, M. A., Lansbury, P. T. and Caughey, B. 1997. Molecular assessment of the potential transmissibilities of BSE and Scrapie to humans. Nature 388 (6639): 285-288.
Saegerman, C., Vanopdenbosch, E. and Berkvens, D. 2007. Current status of Scrapie. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2 (027): 20 pp.
Stack, M., Jeffrey, M., Deslys, J.P., Grassi, J., Baron, T., Safar, J., Groschup, M., Agrimi, U., Langeveld, J., Matthews, D., Hope, J. and Bostock, C., 2008. An evaluation of techniques for the discrimination of natural scrapie and experimental bovine spongiform encephalopathy in sheep. Document available at the Community Reference Laboratory for Transmissible Spongiform Encephalopathies.
http://www.defra.gov.uk/corporate/vla/science/documents/science-tse-rl-ringtrial.pdf
PLEASE READ ;
7 February 2008 - A Statement on the potential human health risk from changes to classical scrapie controls(41 KB) has been published.
http://www.seac.gov.uk/statements/scrapiestatement080207.pdf
16. There is no firm evidence for a link between human TSEs and classical scrapie. Although a link cannot be ruled out, even if there is a link, the human health risk from classical scrapie must be very low and result in very few human TSE cases per annum. This is because the incidence of human TSEs is very low and relatively constant world-wide (around one case per million people per year) showing that there must be at least a substantial, if not complete, barrier to transmission of classical scrapie to humans. Although it is not possible to quantify any increase in risk that would arise from the changes to classical scrapie controls, the increased risk is
6 © SEAC 2008
highly unlikely to be greater than the risk before classical scrapie controls were introduced. Indeed, given the apparent effect of the National Scrapie Plan (NSP) on reducing the incidence of classical scrapie in the UK, the risk, if it exists, is likely to be appreciably lower than prior to the implementation of the NSP controls. 17. It is possible that the changes to the EU controls may increase the level of atypical scrapie entering the food chain from classical scrapie affected flocks with concurrent atypical scrapie infections. However, given the low occurrence of atypical scrapie within flocks, any increase in the potential human health risk from atypical scrapie is likely to be very low.
Summary
18. Although the changes to the classical scrapie controls may increase the potential risks to human health from small ruminant TSEs, any risk that is present is currently very low or negligible and any increased risk likely to be very low or negligible. For classical scrapie, any increase in potential risk will be less than the longterm historic risk prior to the introduction of small ruminant TSE controls. A risk-benefit analysis is required to determine the proportionality of the changes in controls with respect to the increased potential risks. Such an analysis is not within the remit of SEAC.
SEAC February 2008
http://www.seac.gov.uk/statements/scrapiestatement080207.pdf
Thursday, January 31, 2008
SPONGIFORM ENCEPHALOPATHY ADVISORY COMMITTEE Draft minutes of the 99th meeting held on 14th December 2007
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 ............
snip... please see full text, sources, and comments here ;
http://seac992007.blogspot.com/2008/01/spongiform-encephalopathy-advisory.html
USA MAD COW CASES IN ALABAMA AND TEXAS
***PLEASE NOTE***
USA BASE CASE, (ATYPICAL BSE), AND OR TSE (whatever they are calling it today), please note that both the ALABAMA COW, AND THE TEXAS COW, both were ''H-TYPE'', personal communication Detwiler et al Wednesday, August 22, 2007 11:52 PM. ...TSS
http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0708&L=sanet-mg&T=0&P=19779
P02.35 Molecular Features of the Protease-resistant Prion Protein (PrPres) in H- type BSE
Biacabe, A-G1; Jacobs, JG2; Gavier-Widén, D3; Vulin, J1; Langeveld, JPM2; Baron, TGM1 1AFSSA, France; 2CIDC-Lelystad, Netherlands; 3SVA, Sweden
Western blot analyses of PrPres accumulating in the brain of BSE- infected cattle have demonstrated 3 different molecular phenotypes regarding to the apparent molecular masses and glycoform ratios of PrPres bands. We initially described isolates (H-type BSE) essentially characterized by higher PrPres molecular mass and decreased levels of the diglycosylated PrPres band, in contrast to the classical type of BSE. This type is also distinct from another BSE phenotype named L-type BSE, or also BASE (for Bovine Amyloid Spongiform Encephalopathy), mainly characterized by a low representation of the diglycosylated PrPres band as well as a lower PrPres molecular mass. Retrospective molecular studies in France of all available BSE cases older than 8 years old and of part of the other cases identified since the beginning of the exhaustive surveillance of the disease in 20001 allowed to identify 7 H- type BSE cases, among 594 BSE cases that could be classified as classical, L- or H-type BSE. By Western blot analysis of H-type PrPres, we described a remarkable specific feature with antibodies raised against the C-terminal region of PrP that demonstrated the existence of a more C-terminal cleaved form of PrPres (named PrPres#2 ), in addition to the usual PrPres form (PrPres #1). In the unglycosylated form, PrPres #2 migrates at about 14 kDa, compared to 20 kDa for PrPres #1. The proportion of the PrPres#2 in cattle seems to by higher compared to the PrPres#1. Furthermore another PK–resistant fragment at about 7 kDa was detected by some more N-terminal antibodies and presumed to be the result of cleavages of both N- and C- terminal parts of PrP. These singular features were maintained after transmission of the disease to C57Bl/6 mice. The identification of these two additional PrPres fragments (PrPres #2 and 7kDa band) *** reminds features reported respectively in sporadic Creutzfeldt-Jakob disease and in Gerstmann-Sträussler-Scheinker (GSS) syndrome in humans.
FC5.5.1 BASE Transmitted to Primates and MV2 sCJD Subtype Share PrP27-30 and PrPSc C-terminal Truncated Fragments
Zanusso, G1; Commoy, E2; Fasoli, E3; Fiorini, M3; Lescoutra, N4; Ruchoux, MM4; Casalone, C5; Caramelli, M5; Ferrari, S3; Lasmezas, C6; Deslys, J-P4; Monaco, S3 1University of Verona, of Neurological and Visual Sciences, Italy; 2CEA, IMETI/SEPIA, France; 3University of Verona, Neurological and Visual Sciences, Italy; 4IMETI/SEPIA, France; 5IZSPLVA, Italy; 6The Scripps Research Insitute, USA
The etiology of sporadic Creutzfeldt-Jakob disease (sCJD), the most frequent human prion disease, remains still unknown. The marked disease phenotype heterogeneity observed in sCJD is thought to be influenced by the type of proteinase K- resistant prion protein, or PrPSc (type 1 or type 2 according to the electrophoretic mobility of the unglycosylated backbone), and by the host polymorphic Methionine/Valine (M/V) codon 129 of the PRNP. By using a two-dimensional gel electrophoresis (2D-PAGE) and imunoblotting we previously showed that in sCJD, in addition to the PrPSc type, distinct PrPSc C-terminal truncated fragments (CTFs) correlated with different sCJD subtypes. Based on the combination of CTFs and PrPSc type, we distinguished three PrPSc patterns: (i) the first was observed in sCJD with PrPSc type 1 of all genotypes,;
(ii) the second was found in M/M-2 (cortical form); (iii) the third in amyloidogenic M/V- 2 and V/V-2 subtypes (Zanusso et al., JBC 2004) . Recently, we showed that sCJD subtype M/V-2 shared molecular and pathological features with an atypical form of BSE, named BASE, thus suggesting a potential link between the two conditions. This connection was further confirmed after 2D-PAGE analysis, which showed an identical PrPSc signature, including the biochemical pattern of CTFs. To pursue this issue, we obtained brain homogenates from Cynomolgus macaques intracerebrally inoculated with brain homogenates from BASE. Samples were separated by using a twodimensional electrophoresis (2D-PAGE) followed by immunoblotting. We here show that the PrPSc pattern obtained in infected primates is identical to BASE and sCJD MV-2 subtype. *** These data strongly support the link, or at least a common ancestry, between a sCJD subtype and BASE. This work was supported by Neuroprion (FOOD-CT-2004-506579)
FC5.5.2 Transmission of Italian BSE and BASE Isolates in Cattle Results into a Typical BSE Phenotype and a Muscle Wasting Disease
Zanusso, G1; Lombardi, G2; Casalone, C3; D’Angelo, A4; Gelmetti, D2; Torcoli, G2; Barbieri, I2; Corona, C3; Fasoli, E1; Farinazzo, A1; Fiorini, M1; Gelati, M1; Iulini, B3; Tagliavini, F5; Ferrari, S1; Monaco, S1; Caramelli, M3; Capucci, L2 1University of Verona, Neurological and Visual Sciences, Italy; 2IZSLER, Italy; 3IZSPLVA, Italy; 4University of Turin, Animal Pathology, Italy; 5Isituto Carlo Besta, Italy
The clinical phenotype of bovine spongiform encephalopathy has been extensively reported in early accounts of the disorder. Following the introduction of statutory active surveillance, almost all BSE cases have been diagnosed on a pathological/molecular basis, in a pre-symptomatic clinical stage. In recent years, the active surveillance system has uncovered atypical BSE cases, which are characterized by distinct conformers of the PrPSc, named high-type (BSE-H) and low-type (BSE-L), whose clinicopathological phenotypes remain unknown. We recently reported two Italian atypical cases with a PrPSc type similar to BSE-L, pathologically characterized by PrP amyloid plaques. Experimental transmission to TgBov mice has recently disclosed that BASE is caused by a distinct prion strain which is extremely virulent. A major limitation of transmission studies to mice is the lack of reliable information on clinical phenotype of BASE in its natural host. In the present study, we experimentally infected Fresian/Holstein and Alpine/Brown cattle with Italian BSE and BASE isolates by i.c. route. BASE infected cattle showed survival times significantly shorter than BSE, a finding more readily evident in Fresian/Holstein, and in keeping with previous observations in TgBov mice. Clinically, BSE-infected cattle developed a disease phenotype highly comparable with that described in field BSE cases and in experimentally challenged cattle. On the contrary, BASE-inoculated cattle developed an amyotrophic disorder accompanied by mental dullness. The molecular and neuropathological profiles, including PrP deposition pattern, closely matched those observed in the original cases. This study further confirms that BASE is caused by a distinct prion isolate and discloses a novel disease phenotype in cattle, closely resembling the phenotype previous reported in scrapie-inoculated cattle *** and in some subtypes of inherited and sporadic Creutzfeldt-Jakob disease. Oral Abstracts 14
P04.27
Experimental BSE Infection of Non-human Primates: Efficacy of the Oral Route
Holznagel, E1; Yutzy, B1; Deslys, J-P2; Lasmézas, C2; Pocchiari, M3; Ingrosso, L3; Bierke, P4; Schulz-Schaeffer, W5; Motzkus, D6; Hunsmann, G6; Löwer, J1 1Paul-Ehrlich-Institut, Germany; 2Commissariat à l´Energie Atomique, France; 3Instituto Superiore di Sanità, Italy; 4Swedish Institute for Infectious Disease control, Sweden; 5Georg August University, Germany; 6German Primate Center, Germany
Background:
In 2001, a study was initiated in primates to assess the risk for humans to contract BSE through contaminated food. For this purpose, BSE brain was titrated in cynomolgus monkeys.
Aims:
The primary objective is the determination of the minimal infectious dose (MID50) for oral exposure to BSE in a simian model, and, by in doing this, to assess the risk for humans. Secondly, we aimed at examining the course of the disease to identify possible biomarkers.
Methods:
Groups with six monkeys each were orally dosed with lowering amounts of BSE brain: 16g, 5g, 0.5g, 0.05g, and 0.005g. In a second titration study, animals were intracerebrally (i.c.) dosed (50, 5, 0.5, 0.05, and 0.005 mg).
Results:
In an ongoing study, a considerable number of high-dosed macaques already developed simian vCJD upon oral or intracerebral exposure or are at the onset of the clinical phase. However, there are differences in the clinical course between orally and intracerebrally infected animals that may influence the detection of biomarkers.
Conclusions:
Simian vCJD can be easily triggered in cynomolgus monkeys on the oral route using less than 5 g BSE brain homogenate. The difference in the incubation period between 5 g oral and 5 mg i.c. is only 1 year (5 years versus 4 years). However, there are rapid progressors among orally dosed monkeys that develop simian v CJD as fast as intracerebrally inoculated animals.
The work referenced was performed in partial fulfilment of the study “BSE in primates“ supported by the EU (QLK1-2002-01096).
Subject: Aspects of the Cerebellar Neuropathology in Nor98
Date: September 26, 2007 at 4:06 pm PST
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
IS THERE A SCRAPIE-LIKE DISEASE IN CATTLE ?
In April of 1985, a mink rancher in Wisconsin reported a debilitating neurologic disease in his herd which we diagnosed as TME by histopathologic findings confirmed by experimental transmission to mink and squirrel monkeys. The rancher was a ''dead stock'' feeder using mostly (>95%) downer or dead dairy cattle and a few horses. She had never been fed.
We believe that these findings may indicate the presence of a previously unrecognized scrapie-like disease in cattle and wish to alert dairy practitioners to this possibility.
snip...
PROCEEDINGS OF THE SEVENTH ANNUAL WESTERN CONFERENCE FOR FOOD ANIMAL VETERINARY MEDICINE, University of Arizona, March 17-19, 1986
http://www.bseinquiry.gov.uk/files/mb/m09a/tab01.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
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
Epidemiology of Scrapie in the United States 1977
http://www.bseinquiry.gov.uk/files/mb/m08b/tab64.pdf
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
Like lambs to the slaughter
31 March 2001 Debora MacKenzie Magazine issue 2284
FOUR years ago, Terry Singeltary watched his mother die horribly from a degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.
Most doctors believe that sCJD is caused by a prion protein deforming by chance into a killer. But Singeltary thinks otherwise. He is one of a number of campaigners who say that some sCJD, like the variant CJD related to BSE, is caused by eating meat from infected animals. Their suspicions have focused on sheep carrying scrapie, a BSE-like disease that is widespread in flocks across Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight to the campaigners' fears. To their complete surprise, the researchers found that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by some strains of scrapie," says team member Jean-Philippe Deslys of the French Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses, south-west of Paris.
Hans Kretschmar of the University of Göttingen, who coordinates CJD surveillance in Germany, is so concerned by the findings that he now wants to trawl back through past sCJD cases to see if any might have been caused by eating infected mutton or lamb. ...
http://www.newscientist.com/article/mg16922840.300-like-lambs-to-the-slaughter.html
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 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 intracerebral route? Are some VRQ sheep carriers with no neurological symptoms?
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
http://nor-98.blogspot.com/
SCRAPIE USA
http://scrapie-usa.blogspot.com/
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Singeltary, Sr et al. JAMA.2001; 285: 733-734.
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.
To the Editor: In their Research Letter, Dr Gibbons and colleagues1 reported that the annual US death rate due to Creutzfeldt-Jakob disease (CJD) has been stable since 1985. These estimates, however, are based only on reported cases, and do not include misdiagnosed or preclinical cases. It seems to me that misdiagnosis alone would drastically change these figures. An unknown number of persons with a diagnosis of Alzheimer disease in fact may have CJD, although only a small number of these patients receive the postmortem examination necessary to make this diagnosis. Furthermore, only a few states have made CJD reportable. Human and animal transmissible spongiform encephalopathies should be reportable nationwide and internationally.
Terry S. Singeltary, Sr Bacliff, Tex
1. Gibbons RV, Holman RC, Belay ED, Schonberger LB. Creutzfeldt-Jakob disease in the United States: 1979-1998. JAMA. 2000;284:2322-2323. FREE FULL TEXT
http://jama.ama-assn.org/cgi/content/extract/285/6/733?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=singeltary&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
APHIS-2006-0041-0006 TSE advisory committee for the meeting December 15, 2006
http://www.regulations.gov/fdmspublic/ContentViewer?objectId=09000064801f3413&disposition=attachment&contentType=msw8
[Docket No. FSIS-2006-0011] FSIS Harvard Risk Assessment of Bovine Spongiform Encephalopathy (BSE)
http://www.fsis.usda.gov/OPPDE/Comments/2006-0011/2006-0011-1.pdf
[Docket No. 03-025IFA] FSIS Prohibition of the Use of Specified Risk Materials for Human Food and Requirement for the Disposition of Non-Ambulatory Disabled Cattle
http://www.fsis.usda.gov/OPPDE/Comments/03-025IFA/03-025IFA-2.pdf
Attachment to Singeltary comment
January 28, 2007
Greetings APHIS,
I would kindly like to submit the following to ;
BSE; MRR; IMPORTATION OF LIVE BOVINES AND PRODUCTS DERIVED FROM BOVINES [Docket No. APHIS-2006-0041] RIN 0579-AC01
[Federal Register: January 9, 2007 (Volume 72, Number 5)] [Proposed Rules] [Page 1101-1129] From the Federal Register Online via GPO Access [wais.access.gpo.gov] [DOCID:fr09ja07-21]
http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetail&o=09000064801f8152
BSE; MRR; IMPORTATION OF LIVE BOVINES AND PRODUCTS DERIVED FROM BOVINES [Docket No. APHIS-2006-0041] RIN 0579-AC01 Date: January 9, 2007 at 9:08 am PST
http://www.regulations.gov/fdmspublic/component/main?main=DocumentDetail&o=09000064801f3412
USDA CERTIFIED H-BASE MAD COW SCHOOL LUNCH PROGRAM
http://cjdmadcowbaseoct2007.blogspot.com/2008/02/usda-certified-h-base-mad-cow-school.html
Terry S. Singeltary Sr. P.O. Box 42 Bacliff, Texas USA 77518
Subscribe to:
Posts (Atom)