Friday, April 11, 2008




SEAC Annual Report 2007 1 Foreword

The continued decline in the incidence of Bovine Spongiform Encephalopathy (BSE) in the United Kingdom (UK) and elsewhere in Europe is very welcome. As a result, the European Union (EU) has been able to relax some of the control measures introduced to protect human and animal health, and is considering further relaxations. Whilst there are clear economic benefits to relaxing controls, the associated risks may be less well understood. During 2007, SEAC provided advice on the risks that may be associated with changes to specific controls, and advice on how these risks can be assessed. As the effectiveness of one control may be related to that of others, it is important that regulators consider the impact of specific changes, and combinations of changes, on the effectiveness of the control regime as a whole. Furthermore, it is vital that surveillance of animals and humans is in place that is capable of detecting any major adverse consequences of changes to the control regime should these arise. The recent identification of different, albeit apparently rare, forms of BSE, which were discussed by SEAC during the year, emphasises the need for continued vigilance.

It is highly likely that sheep were exposed to BSE during the BSE epidemic in cattle. However, despite extensive Transmissible Spongiform Encephalopathy (TSE) surveillance in sheep there is no evidence that BSE is present in the UK sheep flock now. *{The relatively recent identification of atypical scrapie and paucity of experimental data about its transmissibility either between sheep or to humans have raised concerns about the possible animal and public health implications of this disease}*. Although atypical scrapie has been identified in a number of EU Member States, no clusters of cases have been found. It is, therefore, considered that this disease may have a low rate of transmission between sheep. It is possible, therefore, that atypical scrapie, like classical scrapie, may have existed for some considerable time without any apparent association with human TSEs. Nevertheless, the human health implications need to be clarified. SEAC will continue to monitor closely the results from research underway to assess the human and animal health implications of atypical scrapie. Encouragingly there was only one new diagnosed case of variant Creutzfeldt-Jakob Disease (vCJD) in 2007. However, uncertainty remains about the number of individuals that may be infected with vCJD but who are not showing clinical signs of the disease (subclinical infections). It is critical to ascertain better the prevalence of subclinical infections. This is because the assumed presence of these infections is the reason costly interventions have been introduced (depletion of white blood cells from blood donations, deferral of blood recipients from donating blood and single-use instruments for certain types of surgery and dentistry) to minimise the potential risk of human-to-human transmission of vCJD. During 2007, SEAC reviewed the analysis of the first tranche of results from the National Anonymous Tonsil Archive (NATA). None of the tonsils tested to date (more than 45 000) has been found to be positive for abnormal prion protein.

SEAC Annual Report 2007

Thus, NATA provides no evidence to suggest that a large epidemic of subclinical infections exists. However, there is still uncertainty about how early during the preclinical phase abnormal prion protein accumulates in tonsil tissue and therefore, how reliably tonsil testing is able to detect subclinical infections. It is also the case that, a large proportion of tonsils removed comes from young people with little or no likelihood of dietary exposure to BSE. For these reasons, SEAC continues to stress the need for a post mortem tissue archive to complement the data from NATA. Together NATA and a post mortem tissue archive would allow the wide range of estimated prevalence of subclinical vCJD infections to be narrowed, facilitating better risk assessments of potential human to human transmission of the disease, and analyses to justify costly current and future interventions. New risk assessments considered by SEAC during 2007 suggest that, under certain circumstances, dentistry, like blood transfusion and surgery, may provide a route for vCJD infection to be passed between people. Following advice from SEAC, the Department of Health issued guidance to dentists in 2007 about making certain types of dental instruments single use as a precautionary measure to prevent possible vCJD transmission via certain dental procedures. SEAC strongly encourages the work already underway to improve the decontamination of dental and surgical instruments and to develop blood tests that will allow the risks of vCJD transmission to be reduced. I was pleased to welcome Professors John Collinge and Azra Ghani and Drs Richard Knight and Roland Salmon onto the committee in 2007. I was also pleased to accept my reappointment for a second term as Chair. The committee is very appreciative of the researchers that have shared important unpublished data to allow SEAC and its Subgroups early consideration of important findings. I would like to thank Kate Richards, who moved to a new post during the year, Dr Tom Barlow who stood in as Acting SEAC Secretary, and welcome Dr Peter Grimley as Kate’s successor as SEAC Secretary. I would also like to thank the members of SEAC and its Subgroups for their commitment and the expertise they bring to SEAC and the Secretariat for the support it provides the committee.

Professor Chris Higgins Chair of SEAC

*{The relatively recent identification of atypical scrapie and paucity of experimental data about its transmissibility either between sheep or to humans have raised concerns about the possible animal and public health implications of this disease}*.



The flocks of origin are WY, CO, CA, IN, and MN. personal communication USDA et al. ...TSS

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. 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?



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.

Published online before print October 20, 2005

Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0502296102 Medical Sciences

A newly identified type of scrapie agent can naturally infect sheep with resistant PrP genotypes

( sheep prion transgenic mice )

Annick Le Dur *, Vincent Béringue *, Olivier Andréoletti , Fabienne Reine *, Thanh Lan Laï *, Thierry Baron , Bjørn Bratberg ¶, Jean-Luc Vilotte , Pierre Sarradin **, Sylvie L. Benestad ¶, and Hubert Laude * *Virologie Immunologie Moléculaires and Génétique Biochimique et Cytogénétique, Institut National de la Recherche Agronomique, 78350 Jouy-en-Josas, France; Unité Mixte de Recherche, Institut National de la Recherche Agronomique-Ecole Nationale Vétérinaire de Toulouse, Interactions Hôte Agent Pathogène, 31066 Toulouse, France; Agence Française de Sécurité Sanitaire des Aliments, Unité Agents Transmissibles Non Conventionnels, 69364 Lyon, France; **Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique, 37380 Nouzilly, France; and ¶Department of Pathology, National Veterinary Institute, 0033 Oslo, Norway

Edited by Stanley B. Prusiner, University of California, San Francisco, CA, and approved September 12, 2005 (received for review March 21, 2005)

Scrapie in small ruminants belongs to transmissible spongiform encephalopathies (TSEs), or prion diseases, a family of fatal neurodegenerative disorders that affect humans and animals and can transmit within and between species by ingestion or inoculation. Conversion of the host-encoded prion protein (PrP), normal cellular PrP (PrPc), into a misfolded form, abnormal PrP (PrPSc), plays a key role in TSE transmission and pathogenesis. The intensified surveillance of scrapie in the European Union, together with the improvement of PrPSc detection techniques, has led to the discovery of a growing number of so-called atypical scrapie cases. These include clinical Nor98 cases first identified in Norwegian sheep on the basis of unusual pathological and PrPSc molecular features and "cases" that produced discordant responses in the rapid tests currently applied to the large-scale random screening of slaughtered or fallen animals. Worryingly, a substantial proportion of such cases involved sheep with PrP genotypes known until now to confer natural resistance to conventional scrapie. Here we report that both Nor98 and discordant cases, including three sheep homozygous for the resistant PrPARR allele (A136R154R171), efficiently transmitted the disease to transgenic mice expressing ovine PrP, and that they shared unique biological and biochemical features upon propagation in mice. These observations support the view that a truly infectious TSE agent, unrecognized until recently, infects sheep and goat flocks and may have important implications in terms of scrapie control and public health.


Author contributions: H.L. designed research; A.L.D., V.B., O.A., F.R., T.L.L., J.-L.V., and H.L. performed research; T.B., B.B., P.S., and S.L.B. contributed new reagents/analytic tools; V.B., O.A., and H.L. analyzed data; and H.L. wrote the paper.

A.L.D. and V.B. contributed equally to this work.

To whom correspondence should be addressed.

Hubert Laude, E-mail:

Like lambs to the slaughter

31 March 2001

Debora MacKenzie

Magazine issue 2284

What if you can catch old-fashioned CJD by eating meat from a sheep infected with scrapie?

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 ...

The complete article is 889 words long.

full text;


Adaptation of the bovine spongiform encephalopathy agent to primates and comparison with Creutzfeldt- Jakob disease: Implications for human health Corinne Ida Lasmézas*,, Jean-Guy Fournier*, Virginie Nouvel*, Hermann Boe*, Domíníque Marcé*, François Lamoury*, Nicolas Kopp, Jean-Jacques Hauw§, James Ironside¶, Moira Bruce, Dominique Dormont*, and Jean-Philippe Deslys* * Commissariat à l'Energie Atomique, Service de Neurovirologie, Direction des Sciences du Vivant/Département de Recherche Medicale, Centre de Recherches du Service de Santé des Armées 60-68, Avenue du Général Leclerc, BP 6, 92 265 Fontenay-aux-Roses Cedex, France; Hôpital Neurologique Pierre Wertheimer, 59, Boulevard Pinel, 69003 Lyon, France; § Laboratoire de Neuropathologie, Hôpital de la Salpêtrière, 83, Boulevard de l'Hôpital, 75013 Paris, France; ¶ Creutzfeldt-Jakob Disease Surveillance Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, United Kingdom; and Institute for Animal Health, Neuropathogenesis Unit, West Mains Road, Edinburgh EH9 3JF, United Kingdom

Edited by D. Carleton Gajdusek, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France, and approved December 7, 2000 (received for review October 16, 2000)


There is substantial scientific evidence to support the notion that bovine spongiform encephalopathy (BSE) has contaminated human beings, causing variant Creutzfeldt-Jakob disease (vCJD). This disease has raised concerns about the possibility of an iatrogenic secondary transmission to humans, because the biological properties of the primate-adapted BSE agent are unknown. We show that (i) BSE can be transmitted from primate to primate by intravenous route in 25 months, and (ii) an iatrogenic transmission of vCJD to humans could be readily recognized pathologically, whether it occurs by the central or peripheral route. Strain typing in mice demonstrates that the BSE agent adapts to macaques in the same way as it does to humans and confirms that the BSE agent is responsible for vCJD not only in the United Kingdom but also in France. The agent responsible for French iatrogenic growth hormone-linked CJD taken as a control is very different from vCJD but is similar to that found in one case of sporadic CJD and one sheep scrapie isolate. These data will be key in identifying the origin of human cases of prion disease, including accidental vCJD transmission, and could provide bases for vCJD risk assessment.


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



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. ........


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). ....


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.


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.


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