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From: TSS ()
Risk assessment concerning “the comparability between risks of consuming beef and internal organs regulated by the beef export verification program of the United States/Canada and risks of consuming beef and internal organs of Japanese cattle” December 2005 Food Safety Commission, Japan snip... 2.3 Verfication by surveillance Verification and comparison of subjects and the testing techniques Surveillance in the United States BSE inspection in the United States has been aimed at surveillance, and histopathological tests have been conducted since May 1990 on cattle aged 24 months or older and with central nervous system manifestation or abasia 46). The Animal and Plant Health Inspection Service (APHIS) and the National Veterinary Services Laboratories (NVSL) have introduced an immunohistochemical (IHC) method since 1993 65) 66). The number of tested cattle between 1990 and 2001 was 16,829 67). The number of subject cattle have increased since 2002 to approximately 20,000 high-risk cattle annually, and 57,654 heads of cattle were inspected using histopathological tests and the IHC method between 2002 and May 31, 2004 67). As a result, the first BSE case in the United States was discovered in December 2003. The subsequent epidemiological study reported that this cow was not born in the United States but was imported from Canada 68). After this incidence, according to the advice of the international inspection team, an expanded surveillance began since June 2004 69). In this expanded surveillance, ELISA (enzyme-linked immunosorbent assay) was used in primary test, and the IHC method was used in confirmatory test as before. The number of inspected cattle amount to 383,477 as of July 3, 2005 70). Among them, the second BSE case in the United States was detected in June 2005 71). Note: Breakdown between 1990 and 1993 is unknown (reference data for the consultation in the United States (29)) In the expanded surveillance, a commercial Plateria kit is introduced for the ELISA method (primary test) 72), and is used in a total of 13 institutes including the NVSL and 12 voluntarily participating State Veterinary Diagnostic Laboratories (SVDL) 73). The ELISA method was conducted on 369,467 heads of cattle by May 29, 2005, of which three were tested inconclusive 74), but were tested negative by the IHC method, which was conducted as the confirmatory test. In June 2005, the Office of Inspector General (OIG) demanded confirmatory tests of these three by the Western Blot (WB method). The above diagnosis institutes lacked both a facility and experience of the WB method, thus the National Animal Disease Center (NADC) performed the test, and one was revealed positive. This sample was also tested positive by both the WB and IHC methods at the Veterinary Laboratories Agency (VLA) in Britain. In the United States, the IHC method was performed again using a different antibody, and a positive result was obtained at this time 71) 75). The ELISA had not been conducted before the expanded surveillance in June 2004, neither had the WB method before May 2005. Thus, unlike the young cattle and atypical cases detected by the ELISA and WB method in Japan (tested negative by the IHC method), undetectable BSE cases might have been overlooked by the IHC method in the United States. As a result, the WB method described in the OIE Manual of Standards has been added to the confirmatory test since June 2005 76), however, no official document on details about the WB 21 method that will be introduced in the United States has been presented to the Prion Expert Committee to date. Thus, the surveillance in the United States might have detected more BSE cattle than reported. Surveillance in Canada Canada initiated a surveillance program in 1992. The aim was to identify the presence of BSE in Canada. Several thousands of cattle with central nervous system manifestation or abasia were examined between 1992 and 2003 77) 78). In 1993, BSE infection was confirmed in one cow imported from Britain, and the cow was disposed of without being used in food or feed. At that time, all the cattle imported from Britain was disposed of, and a BSE testing by IHC method took place, but all the cattle were tested negative 79). After the discovery of a BSE cow in May 2003 (the first case in Canada), the aim of the surveillance shifted to the assessment of BSE prevalence in adult cattle, and the expanded surveillance began after the ELISA was introduced in January 2004. In 2004, 23,550 heads of cattle were inspected, and 30,000 are scheduled for inspection annually after 2005 (20,949 were inspected between January 2005 and April 18, 2005). As a result of the initiative, the second case in Canada was discovered on January 2, 2005, and the third case on January 11, 2005 77). Histopathological tests and the IHC method have been introduced to the BSE surveillance in Canada since 1992 and 1994, respectively 79). After the discovery of the first case in Canada, the WB method was introduced in September 2003, and the ELISA in 2004 79). Currently, a simple WB method and the ELISA are performed at state veterinary pathology laboratory, which belong to the TSE inspection organization network, and 6 CFIA network facilities. Positive samples are then sent to the BSE Reference Laboratory in the National Centre for Foreign Animal Diseases (NCFAD) for confirmatory test by the IHC method. However, the WB method is used when the brain stem (obex) cannot be identified anatomically due to sample conditions, or when conflicting results are obtained by a rapid test and the IHC test 78) 80). Surveillance in Japan In Japan, surveillance by histopathological tests of cattle with central nervous system manifestation and others in farms is under operation since 1996 81). Between 1996 and 2001, 2,247 heads of cattle were tested, and the first BSE-positive case was discovered in September 2001 81). Subsequently, test objects and number of cattle expanded sequentially, and as a general rule, dead cattle that are 24 months or older have been included in test objects since April 2003 81). Accordingly, blanket testing of dead cattle aged 24 months or older began in April 2004 81). The ELISA is performed as a primary test at livestock hygiene service centers, and positive samples are tested using the WB method and the IHC method at the National Institute of Animal Health 82). A final diagnosis is made by expert members at the technical research meeting of the risk management organization 82). By the end of September 2005, 202,398 high-risk cattle (those with central nervous system manifestation and dead cattle aged 24 months or older) were tested by the ELISA, and 4 positive cases were detected by the IHC and WB methods. In addition, 788 suspected cases were tested using the ELISA by 2005 (by the time when the 20th case of BSE-positive in Japan was discovered), but no positive cases were detected. 23 In October 2001, BSE screening tests of all slaughtered cattle in slaughterhouses began in order to prevent use of BSE-positive animals in food 12). Primary test is performed by the ELISA, then confirmatory test by the WB method, pathological tests, the IHC method. In BSE testing of slaughtered cattle of all ages, the ELISA is performed as primary test at 114 meat inspection stations throughout Japan (this year’s plan), and positive cases are subjected to secondary test at 3 confirmatory testing laboratories in Japan by the WB method (National Institute of Infectious Diseases and Hokkaido University) and by pathological tests and the IHC method (National Institute of Infectious Diseases and Obihiro University of Agriculture and Veterinary Medicine) 12). By October 31, 2005, 4,974,937 heads of cattle were tested, of which 15 were diagnosed BSE-positive in “the Expert Committee of BSE Diagnosis” of the MHLW 83). The results of this screening test at slaughterhouses are also useful as surveillance data to comprehend the status of BSE contamination correctly. Apparently, improvement of surveillance by adding subject animals, number of subject animals, and test methods, will enable detection of more BSE-positive cattlein many countries, besides in the United States and Canada. snip... 5 Conclusions The past domestic risk assessment could virtually demonstrate the effectiveness and other aspects of the BSE measures, thus assessments have been conducted based on them. However, since the present consultation was conducted outside Japan, assessment of risks of beef and others in the United States and Canada must be based on the assessment of the principles stated in documents, the some data from risk management organizations, and the supplemental remarks of expert members. Thus, it must be taken into account that there were also unclear aspects. In addition, assessment had to be conducted under the assumption that the Beef Export Verification Program was observed. Many points remained unclear in the data from the United States and Canada both in quality and in quantity, and assessment had to be conducted with the assumption that the management measures are observed. Thus, we must say that it is difficult to assess scientifically the comparability of the BSE risks in the United Sates/Canada. On the other hand, assuming that the Beef Export Verification Program presented by the risk management organization (mandatory SRM removal in all cattle, export limitation of age to 20 months or younger, etc.) is observed, the difference in the risk levels of beef and others derived from cattle in the United Sates/Canada and those in Japan is considered very small. The risk management organization holds the responsibility to confirm these assumptions, and if the assumptions are not observed, the results of assessment will be different from the ones presented. If the risk management organization decides to take measures to lift the import ban after consideration of the above-mentioned, the Prion Expert Committee is obliged to receive reports on the effectiveness of the Beef Export Verification Program and the results of assessment of compliance with the Program from the management organization, provided that the assessment was conducted based on the assumptions. Subsequently, the management organization is obliged to report to the public. 6 Supplementary items for conclusion To respond to the present consultation, two points should be emphasized. Firstly, as described in the history of the consultation, the responsibilities of the risk assessment organization and the risk management organization must be defined. When the risk management organization judges and implements measures according to the present verdict, the organization must be accountable of the results to the public, and must hold the responsibility of ensuring compliance with the Beef Export Verification 39 Program by the exporting countries in lifting the import ban. Secondly, to respond to the present consultation, the Prion Expert Committee of the Food Safety Commission compared the differences in the domestic measures in Japan, the United Sates, and Canada. The consultation demands risk assessment, assuming additional conditions for the Beef Export Verification Program for Japan, and the risk assessment was also assessed, assuming the compliance with the Beef Export Verification Program. Thus, establishment of hardware and software for observance of the Beef Export Verification Program and its inspection are most critical. In case the Beef Export Verification Program is not observed, the assessment results are invalid. We would like to add the following points that were controversial in the course of the risk assessment: In terms of SRM removal, the current status of surveillance in slaughterhouses in the United States and Canada is unknown, and the effectiveness of the warranty of good safety by the risk management organization remains uncertain. In particular, contamination of pieces of spinal cord into beef and others can be a risk factor, even in a small amount. In such a case, as for SRM removal, it is unclear whether the risks of beef and others derived from cattle in the United States and Canada are comparable with those in Japan. Thus, the inspection system for spinal cord removal must be reinforced. To accurately comprehend the BSE contamination status in the United States and Canada, and to implement proper management measures, sufficient surveillance of cattle, including healthy animals, must be expanded and maintained. Even if the management measures become effective to some extent, and the epidemic becomes discontinued and localized, or sporadic, at least continuous surveillance of all high-risk cattle must be maintained. To prevent BSE exposure and propagation in the United States and Canada, ban on the use of SRMs, which account for 99.4% infectivity of BSE prion, is essential. The use of SRM must be banned not only in feed for cattle but also in feed of other animals, which might cause cross-contamination. The present risk assessment was conducted under the assumption that the Beef Export Verification Program for Japan was observed. Thus, the management organizations must assure the compliance. The risk management organization must establish a system that assures proper implementation of riskmitigation measures for beef and internal organs that are exported from the United States/Canada to Japan. An accreditation system of slaughterhouses of beef and others exported to Japan as well as a management system, including periodical official on-the-spot inspection of these facilities, are considered effective. Even if the risk management organization decides to lift the export ban, import should be suspended when management measures are not properly observed, such as when certificate of the birth age in months is absent, SRMs are improperly removed, and there is a possible mix-up with beef derived from 40 cattle aged 21 months or older during slaughtering and distribution, all of which lead to a serious situation of undeniable risks to humans. snip... http://www.fsc.go.jp/sonota/bse-risk-assessment-concerning.pdf TSS
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