SEARCH VEGSOURCE:

 

 

Follow Ups | Post Followup | Back to Discussion Board | VegSource
See spam or
inappropriate posts?
Please let us know.
  




From: TSS ()
Subject: Opinion of the Scientific Panel BIOHAZ: Protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants [1]
Date: June 25, 2007 at 11:21 am PST

Opinion of the Scientific Panel BIOHAZ: Protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants [1]
Last updated: 22 June 2007 Publication Date: 22 June 2007

Adopted on 7 June 2007. (Question N° EFSA-Q-2007-055)


Summary

Annex X to Regulation (EC) No 999/2001 lays down rules for the prevention, control and eradication of certain transmissible spongiform encephalopathies and lists the approved rapid tests which may be used within the framework of the EU monitoring programmes. The approval of these tests was based on SSC and EFSA evaluation protocols and its recommendations on the suitability or otherwise of the evaluated tests for inclusion in the EU programme for TSE monitoring.

The EC will now launch a new open call for expressions of interest, for rapid tests for use in the framework of TSE monitoring. This call is intended to cover tests for TSE detection ante- and post-mortem in cattle and sheep and goats. Evaluation of these tests is based on a protocol developed by TSE testing experts and covers different steps including a pre-assessment, an assessment of the application dossier, a laboratory evaluation, approval of the package insert and a field trial. EFSA was asked by the EC to revise and update the three current protocols for the evaluation of TSE tests in ruminants taking into account the experience gained in past evaluation rounds.

This opinion reports on the revised protocol for the evaluation of post mortem TSE tests in small ruminants.

In 2003 the European Commission (EC) (DG SANCO and DG JRC and its IRMM) and EFSA, started evaluation of rapid tests for TSE epidemio-surveillance in small ruminants. During the previous evaluation process, differences were observed between tests in terms of analytical sensitivity. However, the significance of such differences both in term of field diagnostic sensitivity and biological relevance could not be scientifically assessed at the time of evaluation. Moreover, following the implementation of active surveillance programs in the EU using tests that were validated, a new type of TSE (atypical scrapie cases/NOR98) not previously recognized in the EU, was detected in small ruminants. Currently atypical/Nor98 has been detected in a large number of European countries and approximately constitutes 80% of test positive cases identified in EU. Data collected in this EU active surveillance program clearly indicate that all the validated tests do not perform equally toward atypical cases and that difference in performance result in under- or non recognition of various types of scrapie.

The EFSA Scientific Panel on Biological Hazards (BIOHAZ) has agreed on a revised evaluation protocol which takes into account the experience gained in past evaluation rounds and knowledge accumulated from the active surveillance program. New tests have to successfully pass all stages of the evaluation process. Progress to the next stage requires successful completion of the previous stage and therefore the process can be suspended at any stage of the evaluation.

This protocol ensures that newly approved tests will not be inferior to previously approved BSE post mortem screening tests. In addition to previous evaluation criteria, the revised protocol considers each test’s performance with respect to (i) detection of classical scrapie, atypical scrapie and BSE in sheep and (ii) detection of preclinical cases and (iii) limitations posed by analytical sensitivity in comparison with bioassay. The criteria in this revised protocol introduce more comprehensive and higher standards than have previously been approved for validation of small ruminant post mortem TSE tests for classical scrapie and BSE as well as for atypical scrapie. Considering data available about abnormal PrP distribution in the three recognized small ruminants TSE forms (BSE, classical scrapie and atypical scrapie) the use of brainstem appears to be the best compromise for detection of all TSE agents in small ruminants. In consequence, officially confirmed (by CRL and NRL) positive/negative brainstem will be used for the evaluation of tests.

The BIOHAZ panel recommends that tests already approved for the detection of TSE in small ruminants should be required to participate in the new evaluation in order to confirm their robustness and their ability to fulfil the additional performance requirements (e.g. atypical cases and analytical sensitivity). This re-iterates a recommendation of their recent Opinion on the EU TSE Community Reference Laboratory report on batch testing of TSE rapid tests: sample selection and test sensitivity issues[2] . It is further recommended that tests that are not able to meet requirements for detection of all types of TSE (classical scrapie, BSE and atypical scrapie) not be considered for testing small ruminants in the field. Tests that fail to meet a requirement in respect of a particular tissue type (lymphoid/CNS) should not be recommended for application on that tissue. Finally, taking into account the experience gained in the TSE test batch testing protocol and because knowledge in the TSE field is rapidly evolving, the BIOHAZ panel recommends that a system of periodic re-assessment of test approval based on both test field performance and evolving EU policy objectives should be considered by the Risk Managers.


____________________________
[1] For citation purposes: Scientific Opinion of the Panel on Biological Hazards on a request from the European Commission on a protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants. The EFSA Journal (2007) 509, 1-31
[2] For citation purposes: Opinion of the Scientific Panel on Biological Hazards on a request from the European Commission on the CRL report on batch testing of TSE rapid tests: sample selection and test sensitivity issues, The EFSA Journal (2007), 443, 1-18.


http://www.efsa.europa.eu/en/science/biohaz/biohaz_opinions/biohaz_op_ej509_post_mortem_smru.html


Opinion

http://www.efsa.europa.eu/etc/medialib/efsa/science/biohaz/biohaz_opinions/ej509_postmortem_smru.Par.0001.File.dat/biohaz_op_ej509_post_mortem_smru_en.pdf

Summary

http://www.efsa.europa.eu/etc/medialib/efsa/science/biohaz/biohaz_opinions/ej509_postmortem_smru.Par.0002.File.dat/biohaz_op_ej509_post_mortem_smru_summary_en.pdf

Subject: NOR98-LIKE STRAIN OF SCRAPIE FOUND IN WYOMING
Date: April 11, 2007 at 12:47 pm PST

PRESS RELEASE

March 16, 2007

Wyoming Livestock Board

2020 Carey Avenue 4th Floor

Cheyenne, Wyoming 82002

For more information contact: Dr. Walter Cook at (307) 631-2974 [weekend] or (307) 777-6443 [weekday]

*****FOR IMMEDIATE RELEASE*****

NOR98-LIKE STRAIN OF SCRAPIE FOUND IN WYOMING

CHEYENNE, Wyo. - On Friday, March 16, 2007, the Wyoming Livestock Board (WLSB) was notified by officials of the USDA Animal Plant Health Inspection Service (APHIS) that an adult female sheep had tested positive for a form of scrapie consistent with the Nor98 strain. The ewe was slaughtered in Michigan, where it was tested as part of USDA’s regulatory scrapie slaughter surveillance program and traced back to a flock in Wyoming. The results of this case are distinctly different from those seen for bovine spongiform encephalopathy (BSE) or classical scrapie.

Scrapie is a transmissible spongiform encephalopathy and falls into the same category of diseases as chronic wasting disease, found in deer and elk, and bovine spongiform encephalopathy, found in cattle. The disease is limited to sheep and goats and takes years to affect an animal after it has been infected. Scrapie causes sheep to itch and scratch (scrape) wool off, change their behavior and lose body condition; it ultimately ends in death.

Nor98-like scrapie differs from classical scrapie in the distribution of brain lesions and in the course of disease progression and epidemiology. Some sheep that are genetically resistant to the classic form of the disease may be susceptible to the Nor98-like strain. Oddly, Nor98-like scrapie is usually diagnosed during surveillance in animals without clinical signs. There are no known human health risks associated with either form of scrapie.

This is the first time a Nor98-like strain of scrapie has been documented in the United States. It gets the "Nor98-like" name because it is similar to a case first diagnosed in Norway in 1998. This strain of scrapie is a rare disease even in Europe. Since 1998, fewer than 300 cases have been diagnosed in all of Europe. It is usually seen in single animals and does not tend to become widespread in a flock. In contrast, in flocks infected by classical scrapie typically more than 10 percent of the genetically susceptible animals test positive.

"This provides evidence that the surveillance program is working," said Bryce Reece, executive director of the Wyoming Wool Growers Association. "It also indicates that the program is on the cutting-edge of science to detect such a rare disease during standard surveillance."

The Wyoming Livestock Board does not expect the Nor98-like strain of scrapie to become a major disease problem for the sheep industry in Wyoming. Risk is limited because diagnosis of Nor98-like scrapie is usually an incidental event, with even highly-exposed flock mates of the positive animal normally unaffected.

The infected ewe lambed in it in what is considered a low-risk, range-lambing environment. Nonetheless, the WLSB, APHIS and the Wyoming Wool Growers Association plan to assertively pursue this case to make sure that this strain of scrapie is extinguished and does not establish itself in the U.S.

The agencies continue to encourage producers to monitor their sheep for signs of scrapie and other diseases, and to notify their veterinarian if they discover anything unusual.

The positive ewe was purchased as an adult within the last several years and moved to a Wyoming flock near the Black Hills. The producer was notified and his flock quarantined as a precautionary measure. An epidemiologic investigation is ongoing and the producer has been cooperative. The case fits the pattern found in Europe - a single, older sheep that was not exhibiting clinical signs of scrapie.

The regulatory scrapie slaughter surveillance program is a targeted slaughter surveillance program for sheep and goats designed to identify infected animals and flocks. USDA is conducting this surveillance as part of a program to eradicate scrapie from the United States by the end of 2010. Reece said that the sheep industry supports this program and is committed to eliminating scrapie from the United States.

###


http://wlsb.state.wy.us/NewReleases/07Mar16FINALNOR98LIKESCRAPIEPRESSRLS.pdf


SCRAPIE UPDATE USA AS OF MARCH 2007 NOR98 INCLUDED

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

NOR98-LIKE STRAIN OF SCRAPIE FOUND IN WYOMING (1791 lines)
From: Terry S. Singeltary Sr. <[log in to unmask]>
Date: Wed, 11 Apr 2007 15:08:15 -0500


http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0704&L=sanet-mg&T=0&P=8315

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: laude@jouy.inra.fr

www.pnas.org/cgi/doi/10.1073/pnas.0502296102


http://www.pnas.org/cgi/content/abstract/0502296102v1


TSS




Follow Ups:



Post a Followup

Name:
E-mail: (optional)
Subject:

Comments:

Optional Link URL:
Link Title:
Optional Image URL: