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From: TSS ()
Subject: Re: COMMITTEE MEMBERS’ BRIEFING FOR PUBLIC Q & A SESSION AT SEAC 94, 21ST SEPTEMBER 2006
Date: October 15, 2006 at 3:46 pm PST

In Reply to: COMMITTEE MEMBERS’ BRIEFING FOR PUBLIC Q & A SESSION AT SEAC 94, 21ST SEPTEMBER 2006 posted by TSS on October 15, 2006 at 3:06 pm:

6/8/2006 1:19:00 PM


USDA: Much Still Unknown About Two US BSE Cases

WASHINGTON (Dow Jones)--The U.S. Department of Agriculture now believes the only two native-born U.S. cows to contract mad-cow disease were infected with a little understood and rare "atypical" strain that throws into question how the animals were infected.

USDA Chief Veterinarian John Clifford told Dow Jones Newswires this week that the latest two cases of BSE in the U.S. - found in Alabama and Texas – are abnormal, differing from the common form of the disease found in Canada and the U.K.

Clifford also said USDA has no plans to change the way it safeguards the U.S. beef supply.

An internal USDA memo stated, "There is no evidence to justify any changes in surveillance methods, disease control, or public health measures already taken in the United States."

snip...end

http://www.cattlenetwork.com/content.asp?contentid=43386

WHAT BSE/TSE SURVEILLANC OF ANY KIND ??? but a surveillance NOT to find BSE/TSE. ...TSS

USDA Testing Protocols and Quality Assurance Procedures

In November 2004, USDA announced that its rapid screening test produced an inconclusive BSE test result. A contract laboratory ran its rapid screening test on a brain sample collected for testing and produced three high positive reactive results. As required, the contract laboratory forwarded the inconclusive sample to APHIS’ National Veterinary Services Laboratories (NVSL) for confirmation. NVSL repeated the rapid screening test, which again produced three high positive reactive results. Following established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE.

Faced with conflicting results between the rapid screening and IHC tests, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded that no further testing was necessary since testing protocols were followed and the confirmatory test was negative. In our discussions with APHIS officials, they justified their decision to not do additional testing because the IHC test is internationally recognized as the "gold standard" of testing. Also, they believed that

USDA/OIG-A/50601-10-KC/ Page iv

conducting additional tests would undermine confidence in USDA’s testing protocols.

OIG obtained evidence that indicated additional testing was prudent. We came to this conclusion because the rapid screening tests produced six high positive reactive results, the IHC tests conflicted, and various standard operating procedures were not followed. Also, our review of the relevant scientific literature, other countries’ protocols, and discussions with experts led us to conclude that additional confirmatory testing should be considered in the event of conflicting test results.

To maintain objectivity and independence, we requested that USDA’s Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) immunoblot test. The additional testing produced positive results. To confirm, the Secretary of Agriculture requested that an internationally recognized BSE laboratory in Weybridge, England (Weybridge) perform additional testing. Weybridge conducted various tests, including their own IHC tests and three Western blot tests. The tests confirmed that the cow was infected with BSE. The Secretary immediately directed USDA scientists to work with international experts to develop new protocols that include performing dual confirmatory tests in the event of an inconclusive BSE screening test.

We attribute the failure to identify the BSE positive sample to rigid protocols, as well as the lack of adequate quality assurance controls over its testing program. Details of our concerns are discussed in Findings 3 and 4.

snip...

Section 2. Testing Protocols and Quality Assurance Controls In November 2004, USDA announced that its rapid screening test, Bio-Rad Enzyme Linked Immunosorbent Assay (ELISA), produced an inconclusive BSE test result as part of its enhanced BSE surveillance program. The ELISA rapid screening test performed at a BSE contract laboratory produced three high positive reactive results.40 As required,41 the contract laboratory forwarded the inconclusive sample to the APHIS National Veterinary Services Laboratories (NVSL) for confirmatory testing. NVSL repeated the ELISA testing and again produced three high positive reactive results.42 In accordance with its established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE. In addition, NVSL performed a histological43 examination of the tissue and did not detect lesions44 consistent with BSE. Faced with conflicting results, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded no further testing was necessary because testing protocols were followed. In our discussions with APHIS officials, they justified their decision not to do additional testing because the IHC is internationally recognized as the “gold standard.” Also, they believed that conducting additional tests would undermine confidence in USDA’s established testing protocols. However, OIG obtained evidence that indicated additional testing was prudent to ensure that USDA’s testing protocols were effective in detecting BSE and that confidence in USDA’s testing procedures was maintained. OIG came to this conclusion because the rapid tests produced six high positive reactive results, confirmatory testing conflicted with the rapid test results, and various standard operating procedures were not followed. Also, our review of scientific literature, other country protocols, as well as discussions with internationally recognized experts led us to conclude that confirmatory testing should not be limited when conflicting test results are obtained. To maintain objectivity and independence in our assessment, we requested the USDA Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) 40 ELISA test procedures require two additional (duplicate) tests if the initial test is reactive, before final interpretation. If either of the duplicate tests is reactive, the test is deemed inconclusive. 41 Protocol for BSE Contract Laboratories to Receive and Test Bovine Brain Samples and Report Results for BSE Surveillance Standard Operating Procedure (SOP), dated October 26, 2004. 42 The NVSL conducted an ELISA test on the original material tested at the contract laboratory and on two new cuts from the sample tissue. 43 A visual examination of brain tissue by a microscope. 44 A localized pathological change in a bodily organ or tissue.

immunoblot.45 ARS performed the test at the National Animal Disease Center because NVSL did not have the necessary equipment46 (ultracentrifuge) to do the test. APHIS scientists observed and participated, as appropriate, in this effort. The additional tests conducted by ARS produced positive results. To confirm this finding, the Secretary requested the internationally recognized BSE reference laboratory in Weybridge, England, (Weybridge) to perform additional confirmatory testing. Weybridge conducted various tests, including their own IHC methods, as well as three Western blot methods. The tests confirmed that the suspect cow was infected with BSE. Also, Weybridge confirmed this case as an unequivocal positive case of BSE on the basis of IHC. As a result of this finding, the Secretary immediately directed USDA scientists to work with international experts to develop a new protocol that includes performing dual confirmatory tests in the event of another inconclusive BSE screening test. Finding 3 Rigid Protocols Reduced the Likelihood BSE Could be Detected APHIS relied on a single test method, as well as a histological examination of tissue for lesions consistent with BSE, to confirm the presence of BSE even though discrepant test results indicated further testing may be prudent. When IHC test results were interpreted as negative, APHIS concluded the sample tested negative for BSE. Subsequent independent tests initiated by OIG using a different testing method, as well as confirmatory testing by Weybridge, determined that the suspect sample was a positive case of BSE. APHIS Declares BSE Sample Negative Despite Conflicting Results When the tissue sample originally arrived at NVSL in November 2004 from the contract lab, NVSL scientists repeated the ELISA screening test and again produced three high positive reactive results. NVSL scientists cut out two sections of the brain sample for IHC testing. One section was used for an experimental procedure that was not part of the confirmatory testing protocol, and the other cut was for normal IHC testing using scrapie for a positive control.47 According to NVSL scientists, the experimental test results were inconclusive but the IHC test was interpreted as negative. The NVSL scientists were concerned with the inconsistencies and conducted 45 The OIE SAF immunoblot is an internationally recognized confirmatory test, often referred to as a Western blot test. There are different types of Western blots; the OIE SAF immunoblot includes enrichment steps taken with the sample prior to the standard Western blot steps. 46 APHIS has now ordered the necessary equipment for NVSL. USDA/OIG-A/50601-10-KC Page 32

47 A positive control is a sample that is known to contain a given disease or react in the test. The sample then can be used to make sure that the test for that disease works properly. In the case of BSE, tissue infected with either scrapie or BSE can serve as a positive control for an IHC test for BSE since both are different forms of the same disease (transmissible spongiform encephalopathy or TSE).

another IHC test using BSE as a positive control.48 The test result was also interpreted as negative. Also, according to the NVSL scientists, the histological examination of the tissue did not detect lesions consistent with BSE. After the second negative IHC test, NVSL scientists supported doing additional testing. They prepared a plan for additional tests; if those tests had been conducted, BSE may have been detected in the sample. The additional tests recommended by NVSL scientists, but not approved by APHIS Headquarters officials, were the IHC using other antibodies (IHC testing using different antibodies ultimately produced positive results); IHC testing of additional regions of the brain (the cerebellum tested positive); regular and enriched (OIE-like) Western blots (the obex and cerebellum tested positive); and variable rapid tests (the obex and cerebellum tested positive with two different rapid tests). NVSL officials also recommended that the sample be sent to Weybridge for confirmatory testing (to conduct IHC and OIE Western blot tests). In June 2005, Weybridge conducted IHC testing with three different antibodies, including the antibody used in the United States (tested positive), the OIE Western blot (tested positive), a modified commercial kit Western blot (negative) and the NaPTA49 Western blot (tested positive). We obtained information as to the differing protocols used by other countries. We found that while APHIS determined that additional testing was unnecessary after the IHC test, other countries have used multiple tests to confirm positives. In Japan, for example, all reactive screening test samples are examined by both IHC and a Western blot (different from the OIE SAF immunoblot). In the United Kingdom (U.K.), IHC and Western blot (different from the OIE SAF immunoblot) tests are used for all animals that test positive with a screening test. When IHC and the Western blot fail to confirm a positive rapid test, the U.K. resorts to a third test, the OIE SAF immunoblot. With these procedures in place, both Japan and the U.K. have found BSE cases that were rapid test reactive, IHC negative, and finally confirmed positive with a Western blot. Evidence Indicated Additional Testing Would Be Prudent We also spoke with an internationally recognized BSE expert regarding the advisability of limiting confirmatory testing when conflicting results are obtained. This official expressed concern about limiting confirmatory tests to the IHC despite its status as one of the “gold standard” tests. He advised that the IHC is not one test; it is a test method that can vary significantly in sensitivity from laboratory to laboratory. New antibodies can improve or

USDA/OIG-A/50601-10-KC Page 33

48 The NVSL uses scrapie as the positive control as part of its normal IHC testing procedures. Due to the conflicting results between the ELISA and IHC tests, the NVSL conducted another IHC test with BSE as the positive control. Subsequently, the NVSL modified the Confirming Inconclusive Results from BSE Testing Laboratories at the NVSL SOP to show that all IHC tested BSE inconclusive samples from contract laboratories will use BSE as the positive control. 49 Sodium phosphotungstic acid.

USDA/OIG-A/50601-10-KC Page 34

reduce sensitivity, as can variations in many of the reagents50 used. He explained that his laboratory had experienced cases where an initial confirmatory IHC test was challenged by either a more extensive IHC test or “…applying a more sensitive immunoblot.” He emphasized the importance of having additional confirmatory testing to resolve discrepant results since there are many variables, and most of the variability appears to be due to test performance of the laboratory. OIG became concerned that APHIS relied on its confirmatory test methods when rapid screening tests produced high positive reactive results six times.51 Also, we found that APHIS did not pursue and/or investigate why the ELISA produced high reactive positives. An official from the manufacturer of the ELISA test kit told us that they requested, but did not receive, information on the inconclusive reported by USDA in November 2004. These officials requested this information in order to understand the reasons for the discrepant results. The Bio-Rad ELISA rapid screening test is internationally recognized as a highly reliable test and is the rapid screening test used for USDA’s surveillance effort. According to APHIS officials, they felt it would be inappropriate to collaborate on the one sample because Bio-Rad is a USDA-APHIS regulated biologics company and only one of several competing manufacturers. To maintain confidence in USDA’s test protocols, it would have been a prudent course of action for USDA to determine why such significant differing results were obtained. The fact that they did not pursue this matter caused concerns relating to testing quality assurance procedures. In this regard, we found lack of compliance with SOPs relating to laboratory proficiency and quality assurance (see Finding 4), and, in this case, the storage of sampled material and reporting of test results. We found that the NVSL did not prepare a report to document its confirmatory testing of the November 2004 sample. The SOP52 states that the BSE network laboratory initiating the inconclusive will receive a report of the case. NVSL officials could not explain why a final report had not been prepared. We also found that the inconclusive sample was frozen prior to IHC confirmatory testing. APHIS protocols state that samples are not to be frozen prior to laboratory submission. The OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals states that the tissues for histological or IHC examination are not to be frozen as this will provide artefactual53 lesions that may compromise the identification of vacuolation,54 and/or target site location. Although the sample was frozen, APHIS did not conduct a Western 50 A substance used in a chemical reaction to detect, measure, examine, or produce other substances. 51 The six high positive reactive results were from three tests of the submitted sample (multiple runs of the same test). 52 Confirming Inconclusive Results from Bovine Spongiform Encephalopathy Testing Laboratories at the NVSL SOP, dated August 13, 2004. 53 A structure or feature not normally present but visible as a result of an external agent or action, such as one seen in a microscopic specimen after fixation. 54 A small space or cavity in a tissue.

USDA/OIG-A/50601-10-KC Page 35

blot test on the sample. An NVSL official said freezing the sample does not make it unsuitable for IHC. APHIS determined that the sample was suitable for IHC and therefore, in accordance with its SOP, did not conduct a Western blot test. APHIS also handled the December 2003 BSE positive differently than the November 2004 sample. For the December 2003 BSE positive sample, APHIS conducted several confirmatory tests in addition to the IHC testing and histological examination (unlike the November 2004 sample tests, both of these were interpreted as positive). ARS performed two Western blots (Prionics Check Western blot and an ARS developed Western blot). When we questioned why the samples were handled differently, APHIS officials stated that the Western blots were done because the IHC in December 2003 was positive. The additional testing was done to further characterize the case, because it was the first U.S. case; the additional testing was not done to decide whether the case was positive or negative. We discussed our concerns with limiting confirmatory testing, particularly given conflicting results, with the APHIS Administrator and staff in May 2005. He explained that international standards recognized more than one “gold standard” test. In setting up its testing protocols, USDA had chosen one as the confirming test, the IHC test, and stayed with it. APHIS protocols only allow a Western blot in cases where the sample has become unsuitable for IHC tests (e.g., in cases where the brainstem architecture is not evident). International standards, he continued, accept a tissue sample as negative for BSE if its IHC test is negative. Once the test is run in accordance with protocols, additional tests undermine the USDA testing protocol and the surveillance program. He concluded that since APHIS’ protocols accepted the IHC test as confirming the presence or absence of BSE, no further testing was necessary. According to protocol, the tissue sample was determined to have tested negative for BSE. On June 24, 2005, USDA announced that the additional testing by the BSE reference laboratory in England confirmed the presence of BSE in the tissue sample. To obviate the possibility that a future sample would be declared negative and then found positive, the Secretary of Agriculture announced a change to APHIS’ testing protocols that same day. He called for “dual confirmatory tests in the event of another ‘inconclusive’ [reactive] BSE screening test.” He also indicated that he would reinforce proper procedures so that samples will not be frozen, and to spot-check the laboratories to see that they complete reports as required. APHIS issued a SOP on the new confirmatory testing protocols on November 30, 2005.

http://www.usda.gov/oig/webdocs/50601-10-KC.pdf

However, a recently described atypical form of BSE,

termed bovine amyloidotic spongiform encephalopathy (BASE), has modified glycoform

patterns similar to sporadic CJD in humans, and may represent an alternative strain of

BSE agent.18


http://www.aphis.usda.gov/newsroom/hot_issues/bse/content/printable_version/BSE_ongoing_surv_plan_final_71406%20.pdf

A New Form of Mad Cow?

Several studies suggest that, contrary to evidence to date, more than one form of

prion may be involved in BSE

snip...


Now a spate of new findings suggests

that BSE may have its own suite

of related prions. Groups in France,

Japan, and Italy are all claiming to

have identified atypical BSE cases.

And the Italian prion shows molecular

similarity to the one implicated in

a form of human sporadic CJD, although

the researchers are not claiming

a cause-and-effect relation.

The findings may indicate that

either the prions sometimes change

after infecting a new host or that more than

one strain of BSE prion is circulating. Either

way, “I think they’ve found something

new,” says George Carlson, a mouse geneticist

who studies prion diseases at the

McLaughlin Research Institute in Great

Falls, Montana.

At this stage, researchers don’t know

whether this new agent is transmissible. And

because existing tests pick it up, the findings

do not alter the already volatile debate on

what type of cattle surveillance is sufficient

to protect the food supply. But the new findings

do add another piece to the puzzle of

this rare disease.

What scientists consider the most convincing

claim for a new form of BSE was

reported online last week in the Proceedings

of the National Academy of Sciences by a

group led by Maria Caramelli at the National

Reference Center for Animal Encephalopathies

in Turin, Italy, working with

colleagues there and at three other Italian institutes.

Two aged cows, one 15 and one 11,

tested positive on rapid screening tests. The

brains of these animals were preserved, and

further examinations turned up some significant

differences from typical BSE cases. Instead

of the usual granular, stringy deposits

of prions, these atypical cases had amyloid

plaques: globular blobs of tangled protein.

This led the group to propose calling this

new form of the disease bovine amyloidotic

spongiform encephalopathy (BASE).

The molecular weight of the protein is

different, and so is its distribution in the

brain. Usually, BSE primarily affects the

brainstem, hypothalamus, and thalamus. In

the new strain, there were few prions in the

brainstem but more in the olfactory bulb and

cortex and the hippocampus. Both these differences

are similar to the conditions seen in

certain human sporadic CJD cases.

http://www.sciencemag.org/


ALL animals for human/animal consumption must be tested for TSE.

ALL human TSEs must be made reportable Nationally and Internationally...


TSS



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