ADOPTED: 21 October 2020
doi: 10.2903/j.efsa.2020.6307
Evaluation of public and animal health risks in case of a delayed post-mortem inspection in ungulates EFSA Panel on Biological Hazards (BIOHAZ),
Konstantinos Koutsoumanis, Ana Allende, Avelino Alvarez-Ordonez, Declan Bolton, ~ Sara Bover-Cid, Marianne Chemaly, Robert Davies, Alessandra De Cesare, Lieve Herman, Roland Lindqvist, Maarten Nauta, Luisa Peixe, Giuseppe Ru, Marion Simmons, Panagiotis Skandamis, Elisabetta Suffredini, Julio Alvarez S anchez, Bojan Blagojevic, Peter Furst, Bruno Garin-Bastuji, Henrik Elvang Jensen, Peter Paulsen, Katleen Baert, € Federica Barrucci, Alessandro Broglia, Marios Georgiadis, Michaela Hempen and Friederike Hilbert
Abstract
The potential effects of a 24 or 72-h delay in post-mortem inspection (PMI) of ungulates on public health and monitoring of animal health and welfare was evaluated. The assessment used a survey of meat inspectors, expert opinion, literature search and a stochastic model for Salmonella detection sensitivity. Disease detection sensitivity at a delayed PMI is expected to reduce detection sensitivity to a variable extent, depending on the hazard and on the signs/lesions and organs involved. No reduction is expected for Trichinella detection in meat from susceptible animal species and any decrease in detection of transmissible spongiform encephalopathies (TSEs) will not exceed the current tolerance for fallen stock. A 24-h delay in PMI could result in a small reduction in sensitivity of detection for tuberculosis, echinococcosis and cysticercosis. A greater reduction is expected for the detection of pyaemia and Rift valley fever. For the detection of Salmonella, the median model estimates are a reduction of sensitivity of 66.5% (90% probability interval (PI) 0.08–99.75%) after 24-h delay and 94% (90% PI 0.83–100%) after 72-h delay of PMI. Laboratory testing for tuberculosis following a sampling delay of 24–72 h could result in no, or a moderate, decrease in detection depending on the method of confirmation used (PCR, culture, histopathology). For chemical contaminants, a delay in meat inspection of 24 or 72 h is expected to have no impact on the effectiveness of detection of persistent organic pollutants and metals. However, for certain pharmacologically active substances, there will be a reduced effectiveness to detect some of these substances due to potential degradation in the available matrices (tissues and organs) and the non-availability of specific preferred matrices of choice.
© 2020 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority. Keywords: chemical residues, contaminants, delay, lesions, meat inspection, post-mortem, ungulates Requestor: European Commission Question number: EFSA-Q-2019-00124 Correspondence: biohaz@efsa.europa.eu
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2.3. Data and methodology related to TSEs The performance of commercial tests ussed for the statutory screening of carcases for TSE has been formally and extensively evaluated as described in a number of previous EFSA opinions (EFSA 2004, 2005a,b,c, 2007a,b; EFSA BIOHAZ Panel, 2009, 2012). These included the assessment of the effects, if any, of autolysis on both test sensitivity and specificity. The assessment in this opinion is based on these previous evaluations, and their associated references.
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3.4. Assessment of detection at delayed PMI of TSEs
The transmissible spongiform encephalopathies, also known as prion diseases, are a family of fatal neurodegenerative diseases caused by abnormal protease-resistant isoforms (PrPSc) of the normal host-encoded prion protein (PrP). The pathognomonic feature of these diseases is the accumulation of the PrPSc in specific neuroanatomical locations within the central nervous system and, in some instances, in lymphoreticular tissues. These diseases have incubation periods ranging from 18 months to several years depending on the host species, the strain of the agent and the specific genetics of the affected individual, which can influence incubation time, tissue distribution of infectivity and clinical presentation. Animal prion diseases in ungulates include bovine spongiform encephalopathy (BSE) in cattle and goats, scrapie in sheep and goats, chronic wasting disease (CWD) in cervids, and more recently camel prion disease (CPD), some of them with multiple variants/strains. Active surveillance for these diseases has identified previously unknown prion disease variants in a range of species, and these are widely referred to as ‘atypical’ TSE.
For any of these forms of TSE, clinically affected animals may present with a range of non-specific signs such as weight loss/poor condition and reduced milk yields, drooling and/or difficulty in swallowing, and may also show nervousness, an abnormal gait/ataxia, pruritus and/or tremors. Circling may also be a feature of the disease, particularly in small ruminants, and cattle with atypical BSE may exhibit depression, dullness, unresponsiveness and difficulty in rising. None of these clinical signs, individually or in combination, are considered pathognomonic of these diseases, although they should be sufficient to trigger clinical suspicion of TSE on the farm or at AMI. Disease then needs to be confirmed by post-mortem testing.
However, the clinical signs associated with prion diseases occur very late in an otherwise asymptomatic incubation period that could last for years and are not a sensitive or reliable way to detect infected animals, and there is currently no live animal test. Both the detection of infection and/ or disease and the confirmation of clinical suspicion require the post-mortem demonstration of abnormal prion protein in brain and/or lymphoid tissues using immunodetection methods. Even with these methods, there is still a ‘latent period’ post exposure in which there are no methods currently available to detect such recently infected animals (Arnold et al., 2007; EFSA BIOHAZ Panel, 2014, 2017).
3.4.1. TSE testing requirements
TSE testing requirements for all species have changed over time and are stipulated in the consolidated Commission Regulation (EC) 999/2001.35
3.4.1.1. Cattle
At the height of the BSE epidemic, there was a food safely requirement to test all healthy slaughter (HS) cattle over the age of 30 months. Following any positive screening test, the whole carcass (plus the one before and two after on the line) were removed from the food chain and disposed of as Category 1 Animal By-Products (ABP). Over time the age threshold for testing increased, and since 2013, most MS have been allowed to discontinue the testing of HS cattle.
The testing of any HS cattle is now undertaken in only two MS, and solely for the purpose of disease surveillance. When HS testing is undertaken, carcasses must not be released from the slaughterhouse until a negative test result has been received. All MS are obliged to test for TSE in animals that are clinically suspect (including at ante-mortem examination), dead in transit, culled in the context of disease eradication schemes or are fallen stock or emergency slaughtered animals of different ages (for more details, see 2018 EUSR TSE (EFSA, 2019)). There is no specified timeframe for this testing, and samples may be batched for logistical reasons, therefore, a sample may not be tested for several days after the death of the animal.
BSE prevalence is now very low. In 2018 (EFSA, 2019), a total of 1,181,997 cattle were tested, with a total of four cases detected in two MS (1 C-BSE, 1 L-BSE and 2 H-BSE).
35 Regulation (EC) No 999/2001 of the European Parliament and of the Council of 22 May 2001 laying down rules for the prevention, control and eradication of certain transmissible spongiform encephalopathies. OJ L 147, 31.5.2001, p. 1–40.
3.4.1.2. Small ruminants
The testing of annual samples of the adult sheep and goat populations in each MS is required for disease surveillance purposes. The sheep and goat populations are considered separately. The sample size is based on the size of the adult standing population, varies with the surveillance stream and ranges from 0 tested in the SHC (slaughtered for human consumption) category if the national population is less than 750,000, up to 10,000 animals if the standing population is larger than 750,000. These samples can be all SHC, or replaced with up to 5,000 animals not slaughtered for human consumption (NSHC) at the discretion of the MS. In the case of animals NSHC, the number ranges from 0 up to 100 animals if the total population is less than 40,000, and up to 10,000 in MS with an adult population above 750,000. There is no requirement for systematic testing of SHC animals from a food safety perspective. However, the carcass of any SHC animal that is tested is held until the results are available, and any ‘test positives’ are removed from the food chain and disposed of as category 1 ABP.
In 2018 (EFSA, 2019), a total of 325,386 sheep and 138,128 goats were tested, resulting in the detection of a total of 934 cases of scrapie in sheep and 523 in goats.
3.4.1.3. Cervids
Historically, testing for cervid TSE within the EU has been confined to passive surveillance, with the exception of one period during which a survey was conducted in certain MS during the BSE epidemic (EFSA BIOHAZ Panel, 2010). Following the identification of TSE in reindeer, moose and red deer in Norway (Benestad et al., 2016; Pirisinu et al., 2018; Vikøren et al., 2019) a mandatory 3-year active surveillance programme was proposed (EFSA BIOHAZ Panel, 2017) that has been implemented in Estonia, Finland, Latvia, Lithuania, Poland and Sweden as of 2018. The selection of animals for this surveillance programme is focussed on the high-risk groups for two main management systems, i.e.
• from the farmed or captive population, and in order of priority (surveillance value) animals which are fallen/culled, clinical/sick, slaughtered farmed cervids which have been declared unfit for human consumption and finally slaughtered farmed cervids considered fit for human consumption,
• From the wild/semi-domesticated population, and in order of priority (surveillance value) animals which are fallen/culled, road- or predator-injured or killed, clinical/sick, wild hunted cervids and slaughtered semi-domesticated cervids which have been declared unfit for human consumption, and finally hunted wild game and slaughtered semi-domesticated cervids considered fit for human consumption.
There is no current requirement for the testing of SHC animals from a food safety perspective.
In 2018, 5,110 animals were tested in the context of the mandatory cervid surveillance programme, and one positive moose (a fallen wild animal) was identified in Finland. The voluntary testing of a further 3,075 animals in other MS did not result in any other positive animals being identified (EFSA, 2019). The majority (67%) of the animals tested came from the lowest priority (SHC) population. In 2019, a further three positive cases have been detected, all wild moose from Sweden (two clinically abnormal animals that were culled, and one apparently healthy hunter-killed animal) (EFSA BIOHAZ Panel, 2019).
3.4.2. TSE testing protocols
Primary screening for TSE is usually conducted using ELISA-based ‘rapid tests’ regardless of the species or tissue being tested. Such testing will report a ‘presence/absence’ of abnormal PrPSc, but subsequent confirmation of disease, and its classification, is delivered by confirmatory testing which is usually immunohistochemistry or Western Blotting, although a second ELISA with different antibodies is acceptable (OIE manual).36
A key feature of the disease-specific protein PrPSc is that it is proteinase-K resistant, a feature that is exploited by many testing protocols. This also means that it is at least partially resistant to other proteases and persists even when tissue is markedly autolysed. Studies looking at test performance in known positive autolysed samples show no reduction in analytical sensitivity or specificity even with advanced autolysis (Chaplin et al., 2002; Monleon et al., 2003; EFSA, 2004; Wear et al., 2005; EFSA BIOHAZ Panel, 2012; Sarasa et al., 2013). However, such studies have not been carried out for goat scrapie, for atypical forms of disease (in which the PrPSc has been shown to be more sensitive to protease digestion (Everest et al., 2006; Klingeborn et al., 2006)), or for the newly identified European cervid TSE. It is hypothetically possible that there are unknown forms of disease in which the abnormal protein is more protease-sensitive and are therefore not detected by any current testing strategy.
Due to the very precise and restricted neuroanatomical location of the abnormal protein in the early stages of the incubation period, accurate subsampling of the brainstem, at the level of the obex, is required to ensure that tissues from the appropriate neuroanatomical areas are available for both the screening test and the confirmatory test (Arnold et al., 2007; Ryder et al., 2009; EFSA BIOHAZ Panel, 2017, 2018, https://science.vla.gov.uk/tse-lab-net/documents/tse-oie-rl-samp.pdf). This is compromised if poor tissue preservation prevents anatomical orientation of the sample, or if tissue integrity is completely lost. Test specificity remains unaltered, so a positive result is valid, but a negative result is less reliable if the neuroanatomical origin of the tissue presented to the test cannot be confirmed. This aspect of testing has the most substantial effect on the overall sensitivity of any TSE testing protocol. For example, the EFSA (2015) report on negligible scrapie risk (Denmark) states – ‘the existing laboratory data on the sensitivity of the screening diagnostic tests from past EU test evaluations are not representative of the sensitivity under field conditions, and may result in an overestimation of the surveillance sensitivity’.
Current sampling protocols are based on the neuroanatomical areas known to be the first to accumulate detectable PrPSc in classical forms of disease in cattle and small ruminants, and in the majority of cases of CWD. Atypical and newly identified forms of disease also involve these areas, although the neuropathogenesis of these alternative disease presentations is yet to be established. In animals in which disease pathogenesis includes an initial peripheral lymphoid stage, such animals would be detected earlier in the incubation period if lymphoid tissue is sampled than would be possible if only brainstem was sampled for testing. However, lymphoid testing alone would fail to identify those animals with no detectable involvement of the lymphoid system. Greater overall diagnostic sensitivity would be achievable by the dual sampling of brainstem with lymph node, as recommended for the current cervid surveillance.
In summary, the current testing requirements for TSE are driven by disease surveillance, rather than food safety, as a direct objective, and focus primarily on animals not slaughtered for human consumption. Delays of several days before the sampling and testing of fallen stock are accepted. Should the testing of HS be maintained, introduced or reintroduced for any species, delays in PMI of 24 or 72 h could potentially reduce the overall diagnostic sensitivity of the testing programme through the effects autolysis may have on tissue integrity and the ability to identify and sample specific neuroanatomical areas with accuracy, but will not exceed the tolerance already in place for fallen stock. Uncertainties about the effect of a delayed PMI on the detection of TSEs are summarised in Appendices D.1 and E.
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Assessment question 2: Is the detection of transmissible spongiform encephalopathies (TSEs) in cattle, sheep, goats and cervids and Trichinella in Suidae and solipeds reduced if the PMI is delayed by 24 or 72 h after slaughter/arrival in the game-handling establishment?
• Delays in PMI of 24 or 72 h could potentially reduce diagnostic sensitivity of the testing programme if autolysis was to compromise sampling accuracy. However, this would not exceed the tolerance already in place for fallen stock surveillance sampling. The analytical sensitivity and specificity of TSE laboratory tests have been shown to be unaffected by delays of this duration.
• For the detection of Trichinella the panel did not find any evidence that would suggest a decrease in sensitivity during cold storage and it is almost certain (99–100%) that there is no decrease in sensitivity of detection after a delay of PMI of 24 or 72 h.
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5. Recommendations
• There are large data gaps regarding how the PMI detection of pathological and morphological changes might alter following 24-h or 72-h chilled storage. If a delayed PMI regime is established, Member States should keep track of any changes in the number of recorded lesions.
• Due to the lack of information regarding the frequency, pattern, severity and post-mortem stability of the lesions in subclinical or asymptomatic cases, and, consequently, the high uncertainty about the reduction of detectability of certain disease lesions after a 24-h delay of PMI, and an even greater discrepancy after a 72-h delay, there is a need for studies addressing these issues for diseases listed according to article 5 of Regulation (EC) 2016/429. Such studies could help identify situations where it might be advisable to limit the use of delayed PMI.
• Additional training of official veterinarians and meat inspectors might be necessary to provide efficient PMI when performed at delay of 24 or 72 h after slaughter.
• An extended storage period of 24–72 h of carcasses before PMI will increase the time for possible cross-contamination between carcasses, aerosols and dust. Thus, it is expected that carcasses and offal not yet declared fit or not fit for human consumption might be stored together and thus, increase the risk of cross-contamination by zoonotic and animal pathogens. This would need to be considered if such a delay was implemented.
• There is a need for studies on the post-mortem stability, particularly for pharmacologically active substances in different matrices other than urine and plasma.
References
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Appendix D – Uncertainty assessment for TSE, Trichinella and Salmonella
D.1. Uncertainty table TSE
Factor, parameter or model feature affected by the uncertainty
One sentence description of the cause of uncertainty affecting this factor, parameter or model feature (one row per cause of uncertainty)
One sentence description of how this source of uncertainty might lead to incorrect answer, or why that might be possible
Structural integrity of the brain/brainstem at the time of sampling
The analytical sensitivity and specificity of PrPSc detection methods are unaffected by autolysis, but if structural integrity is lost due to autolysis following delayed sampling, it may not be possible to take the correct anatomical areas, or to ensure that the correct areas have been included in the sample. False negatives may occur if the wrong area is sampled. An inaccurately sampled positive case may have insufficient anatomically correct tissue to enable the confirmatory diagnostic step to be performed
It is almost certain that autolysis would be limited in the controlled environment of chilled storage for 24 or 72 h after slaughter and would not exceed the tolerance already in place for fallen stock
i wonder if a 7 month delay on a suspect BSE case in Texas is too long, on a 48 hour turnaround, asking for a friend???
I am sure that most of you are aware of the Texas mad cow cases that were covered up. the 1st documented cover-up was successful, the second documented case of mad cow in Texas would have been successful, but after literally, an act of Congress to override Austin, Texas officials (rick perry), only after the Honorable Fong of the OIG, and scientist all over the world, and a few others, including myself wrote to the OIG about said cover-up, and 7 months later, did they finally retest that covered-up highly suspect mad cow, and said covered up mad cow was finally _confirmed_ by Weybridge as a confirmed Texas BSE mad cow case. this 7 months after the fact on a Government BSE REDBOOK regulations of a 48 turn around on said test. over course this was all done for a reason, the BSE MRR policy was being put into place while all this was going on, and Heaven forbid if rick perry would have had a confirmed BSE mad cow case while those regulations were over riding the BSE GBR risk assessments. however, during all this political science on mad cow disease, it was nothing more than a crap shoot, and 15 years later, we now know that some of the sporadic CJD cases are indeed tied to the atypical BSE cases here in North America. How many people during the Bush/Perry era, how many did they needlessly expose to mad cow disease? how many will go clinical and die in the decades to come? Whether or not you dare care, during the Bush/Perry era, they exposed our kids to mad cow disease, by feeding them dead stock downer cows via the NSLP, for over 4 years. DEAD STOCK DOWNER COWS ARE THE MOST HIGH RISK COW FOR MAD COW DISEASE. WHO will watch the children for the next 5 decades for CJD ???
Sunday, May 18, 2008
BSE Inquiry DRAFT FACTUAL ACCOUNT DFA
BSE Inquiry DRAFT FACTUAL ACCOUNTS DFA's
DFA 15 Monitoring and Enforcement of the SBO Specified Bovine Offal Regulations
SATURDAY, AUGUST 26, 2017
DFA 14 Consideration of the Risk from Mechanically Recovered Meat (MRM) in 1989-1990
BSE INQUIRY DFA 16 MID 1995 TO THE FINAL DAYS
MONDAY, NOVEMBER 23, 2020
Chronic Wasting Disease CWD TSE Prion Cervid State by State and Global Update November 2020
MONDAY, NOVEMBER 30, 2020
REPORT OF THE MEETING OF THE OIE SCIENTIFIC COMMISSION FOR ANIMAL DISEASES Paris, 9–13 September 2019 BSE, TSE, PRION
Monday, November 30, 2020
Tunisia has become the second country after Algeria to detect a case of CPD within a year
TUESDAY, NOVEMBER 17, 2020
The European Union summary report on surveillance for the presence of transmissible spongiform encephalopathies (TSE) in 2019 First published 17 November 2020
WEDNESDAY, OCTOBER 28, 2020
EFSA Annual report of the Scientific Network on BSE-TSE 2020 Singeltary Submission
WEDNESDAY, OCTOBER 28, 2020
EFSA Scientific Opinion Potential BSE risk posed by the use of ruminant collagen and gelatine in feed for non‐ruminant farmed animals
TUESDAY, DECEMBER 01, 2020
Sporadic Creutzfeldt Jakob Disease sCJD and Human TSE Prion Annual Report December 14, 2020
Terry S. Singeltary Sr.
