Public summary of the meeting on
28th February 2001

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The Spongiform Encephalopathy Advisory Committee (SEAC) met in London on 28 February 2001.

Council decisions and imports

Epidemiology and testing

Members considered current and future proposals for active BSE surveillance of UK cattle using diagnostic tests on cattle brains. Under new EU regulations, annual testing of 9,000 UK fallen cattle aged over thirty months began in January 2001 (Fallen cattle are animals which are found dead on farm - these animals are not subject to veterinary inspection and hence are not allowed to enter the human food chain regardless of the OTMS). Members noted that under recent EU decisions, the UK will almost certainly be required to test all OTM fallen cattle (75,000 animals annually estimated for GB); OTMS cattle born August 96-July 97 (100,000 GB animals annually) and from later this year, all casualty animals (100,000 GB animals annually).

Members considered the plans for, and the results of, BSE testing in other EU Member States. All cattle over thirty months of age entering the food chain must now be tested for the presence of BSE prions using one of three approved diagnostic tests. Other than the small number of cattle that are slaughtered under the Beef Assurance Scheme, this testing does not apply to the UK because OTM cattle are not permitted to enter the human food chain here. Members agreed that the current diagnostic tests are useful tools for epidemiological surveillance and would help to give much better data on the distribution of BSE in the EU. However, the tests had limited public health protection value when used to screen out infected cattle in abattoirs. To date, the tests had only been validated using brain material derived from animals with clinical BSE. Although the Committee considered that the current diagnostic tests would be able to detect BSE infection in the late pre-clinical phase of disease (probably about three months before clinical disease appears), infected cattle earlier in the incubation period would not be detected by current testing regimes being used in other Member States. Members emphasised the pressing need to develop diagnostic tests that are able to detect animals in the early phases of infection, and stressed the importance of work to assess the sensitivity of BSE diagnostic tests throughout the incubation period. This was an EU-wide issue.

Members expressed concern about results from a recent survey of casualty animals over thirty months of age in Northern Ireland which indicated evidence of BSE infection in about 2% of the 2546 animals sampled. Although these samples were taken from a group of OTM cattle which would not have entered the food chain, Members considered that the results appeared to be at some variance with the low incidence of reported clinical BSE in Northern Ireland and requested further information at the next meeting.

Implementation of EU specified risk material legislation including Pithing

Members were updated on progress in implementing the EU legislation on specified risk material. They were informed that the extension of the EU controls to include the entire intestine of all bovines had been implemented in the UK from 01 January 2001 and that implementing legislation was in place to ban pithing of cattle, sheep and goats whose meat is intended for human or animal consumption from 01 April 2001.

In relation to this agenda item, Members asked for information about the use of catgut, which is manufactured from cattle intestines and used for surgical stitches in human and veterinary medicine. In terms of human health, it was recognised that the medical use of catgut sutures was being reviewed by the Medical Devices Agency (MDA), an Executive Agency of the Department of Health. SEAC welcomed the news that the MDA were in the process of informing the NHS about the decision of the manufacturers to stop supplying catgut sutures to the UK market. SEAC acknowledged that the decision to cease supply of catgut sutures in the UK was facilitated by the adequate supply of acceptable, alternative synthetic sutures. (Further information on catgut sutures is available on the Medical Devices Agency website). Members requested clarification of whether current EU legislation classifying cattle ileum as a specified risk material prevents it's use for cat gut and asked that further information on its use in veterinary surgery should be provided at the next meeting.)

Animal feed ban

Members considered a number of EU-wide animal feed regulations which had been adopted temporarily in the light of the emerging BSE epidemic elsewhere in Europe. The regulations currently apply only until June 2001 and prohibit the feeding of processed animal protein to all farmed livestock, as opposed to merely ruminants. This brings Members States broadly in line with current UK legislation adopted in 1996. SEAC strongly agreed that the widened EU feed ban was beneficial to the protection of animal health and, in major part, should be made permanent.

On specific animal feed issues, Members agreed that meal derived from wild fish could be exempt from the feed ban. In order to prevent intra-species recycling, meal derived from farmed fish should be allowed only if it could be guaranteed that it would not be fed to farmed fish, either directly or indirectly via meal from other species. If this could not be guaranteed then it should not be used.

Imports of beef and beef products

The Committee was informed of the conclusions of a sub-group of SEAC which had met on 05 December 2000 to consider the risk from imported beef and beef products. The sub-group had welcomed the introduction of an EU requirement that from 01 January 2001 cattle aged over thirty months would not be allowed to enter the food chain unless they had tested negative for BSE using one of the EU-approved rapid tests. It had, however, expressed concern that, because of the limitations of these tests, a negative result would not necessarily mean that the animal was free of infection. The sub-group therefore considered that the UK's over-thirty-month (OTM) rule should continue to apply to imported meat until questions concerning the efficacy of the tests had been resolved. The sub-group had also expressed concern that the OTM rule did not apply to imports and sales of processed meat products.

The FSA reported on the statements it had subsequently made, recommending retention in the UK of the existing controls, including the OTM rule, and advising that legally-sold imported French beef posed no significantly greater risk than UK beef. The latter statement had, however, made clear that processed meat products from countries where BSE had been recorded might pose a slightly higher risk than legally-sold carcase meat, because they might contain beef from OTM animals. The FSA also informed the Committee that the EU SRM rules would permit trade in bovine head meat from all EU Member States except UK and Portugal.

In discussion, the Committee endorsed the conclusion of the sub-group that the OTM rule should continue to apply to imported carcase meat and confirmed that it continued to have a particular concern about the safety of imported meat products, given that they were not covered by the OTM rule. The Committee noted the FSA's statement on the safety of imported beef, but suggested that the position on French beef would need to be kept under review and that the assessment of the risks from imports should be made more comprehensive and include live animals. On bovine head meat, the Committee expressed concern about the possibility of contamination by brain material and recommended that a case for extending the SRM rules to include the whole head be made to the European Commission.

Results of modelling work on BSE in Ireland and France

Dr Christl Donnelly of Imperial College presented interim modelling work on BSE in the Republic of Ireland, using the techniques previously applied to French data. While stressing that the work was not yet complete and might be subject to change with additional information, Dr Donnelly presented estimates* of the number of animals which had been infected with BSE in Ireland and the number of these which had been slaughtered for food. Assuming that BSE had been under-reported in Ireland, her estimate was that, in the year 2000, 150 infected animals were slaughtered for human consumption in Ireland, of which 72 were within 12 months of clinical onset of the disease (the comparable estimates for UK and France being 1 and 52 respectively). Taking account of herd sizes, the relative risks were roughly 99 times greater in Ireland than Great Britain, compared with roughly 24 times greater in France than Great Britain. If the OTM rule were fully enforced, the risk of consuming Irish meat in the UK would however be essentially zero, as none of the cattle within 12 months of developing clinical disease would be consumed in the UK. But if enforcement fell short, then the relative risk would rise in proportion to the level of deficiency of enforcement. Overall, however, the relative risk from Irish beef, even if no account were taken of the OTM rule, was much lower than that from consumption of British cattle before the OTM rule came into force in March 1996. Dr Donnelly's final assessment of BSE risk in Irish beef was published on the FSA website on 22 March 2001. The final results indicated that a total of 159 animals estimated to have been within 12 months of clinical symptoms of BSE entered the food chain in the Republic of Ireland in 2000. The relative likelihood for carcase meat imported from Ireland compared with that originating in Great Britain is about twice if the OTM rule is enforced on 99% of imports as is indicated by returns to the FSA.

Members considered current data on BSE cases in the UK and in other EC Members States. The rising number of infected animals in other Member States was a cause for concern, particularly the high proportion of 1996 (and possibly 1998) born cases in Germany, which may imply a continuing epidemic.

*These results were interim data which were correct at the time of the meeting. The final results of Dr Donnelly's work can now be found on :http://www.bsereview.org.uk/templates/latest/ite

Sheep

At its meeting in November 2000, SEAC had agreed to set up a small sub group to consider the basic principles underlying the National Scrapie Plan (NSP). Since then, the sub-group had met and Members considered their conclusions, which noted that there was increasing scientific evidence to suggest that animals carrying the ARR allele of the prion protein gene, a version of the gene which confers resistance to scrapie and experimental BSE, were not sub-clinical reservoirs of infectivity. The subgroup agreed that implementation of the NSP based on selective breeding to increase the prevalence of the ARR allele in the national flock and decrease the level of PrP genotypes known to be susceptible to scrapie was a valid and important approach. The sub-group recommended that the breeding programme should proceed and, in parallel, further work should be undertaken to verify that sheep naturally exposed to scrapie and sheep experimentally challenged with BSE, but carrying alleles associated with resistance to TSEs do not harbour infectivity or PrP^Sc in the absence of clinical signs of disease. The sub-group considered that if experimental results came to light that implied that genetically resistant sheep were able to replicate and harbour the scrapie agent, the National Scrapie Plan should be reviewed. SEAC accepted the conclusions of the sub-group and endorsed their recommendations. A summary of the sheep sub-group conclusions is given in the Annex to this Public Summary.

SEAC also briefly considered current proposals of phase III of the NSP concerning scrapie-affected flocks. SEAC agreed that dealing with scrapie-affected flocks was the other important element of the NSP to reduce levels of scrapie and that it was important, as with the breeding for resistance scheme, to have a voluntary scheme in the first instance. It was agreed that a SEAC subgroup should consider phase III of the NSP in more detail and that their conclusions would be fed back to the main Committee.

Risk assessment on small incinerators

In September 2000, Members had agreed the terms of reference for an independent study on the potential risks to human health from small incinerators burning SRM. A draft version of the report was tabled which indicated that the risk from such incinerators would be expected to be negligible. Because of a shortage of time and the complexity of the subject, Members agreed to convene a small working group to discuss the risk assessment in detail and report back to the full Committee at the next meeting.

Current Health Issues

Variant Creutzfeldt Jakob Disease (vCJD) Update

The Committee conducted its regular review of epidemiological information on vCJD. The Committee was informed that the total number of definite or probable vCJD cases stood at 95, of whom 6 were still alive. A number of geographically associated cases were being investigated in conjunction with the National CJD Surveillance Unit, Communicable Disease Surveillance Centre/Public Health Laboratory Service; the London School of Hygiene and Tropical Medicine; and the Department of Health. A national protocol to ensure consistency of investigation of such cases was in an advanced stage of preparation. The Committee noted that the trend showing a 20-30% increase, year-on-year, in the number of vCJD cases was currently being maintained.

Safety of Human blood

The Committee considered a risk assessment of the potential impact on vCJD person-to-person transmission of ceasing to use UK donor plasma in the production of fresh frozen plasma (FFP). The Committee accepted that if FFP were sourced from outside the UK, the theoretical vCJD risk from FFP could be minimised further, but there might also be an increased risk from other infectious agents associated with such a change. It was explained that the Microbiological Safety of Blood and Tissues for Transplantation (MSBT) Committee would shortly be re-examining the risk assessment in the light of SEAC views. The Committee did not dissent from the risk assessment's conclusions, but considered that it was important for the report to be set in context and reflect uncertainty.

More generally, SEAC noted and welcomed efforts being made to secure the better use of blood so as to reduce the need for transfusion, and research underway to develop synthetic alternatives.

Update on decontamination of surgical instruments

The Committee noted the Department of Health press release of 04 January announcing new measures to modernise NHS decontamination and sterilisation facilities and introduce single use instruments for tonsil surgery, to further minimise the theoretical risk of transmission of vCJD in hospitals.

SEAC welcomed consultations which were underway between the Department, the Royal College of Surgeons, manufacturers of surgical equipment and others to explore the possible introduction of single use instruments for certain other procedures.

Update on CJD incidents panel

SEAC was updated on developments concerning the CJD Incidents Panel following its second meeting on 22/23 February 2001. The Committee was informed that the panel is drawing up guidance on the quarantine of instruments and guidance on informing those who may have been inadvertently exposed to vCJD.

SEAC/ACDP TSE Joint working group

This item was deferred until the next meeting in April.

DH R&D update

The Committee received its regular update on research sponsored and commissioned by the Department of Health. In particular, it noted a report on a recent meeting organised by the Transmissible Spongiform Encephalopathy Joint Funders' Group to encourage research on diagnostic tests, through bringing together academics, commercial companies and others interested in this field. A call for proposals for diagnostics would be issued soon.

MAFF R&D update

The Committee conducted its regular review of research findings and epidemiological information on BSE. SEAC noted that in ongoing experiments to examine the pathogenesis of experimental BSE in sheep, Romney, Suffolk and Cheviot sheep of susceptible genotype had shown evidence of infectivity in their tissues early in the incubation period. However, encouragingly, no tissues from sheep ARR homozygote sheep (i.e. animals carrying two copies of the ARR version of the gene) had yet been found to be positive.

DELFIA results

Dr Barnard from Southampton General Hospital presented an overview of the technology underlying the time resolved dissociation-enhanced fluoroimmunoassay (DELFIA) diagnostic test for BSE. Initial technical problems related to sample preparation which gave rise to an unexpectedly high number of positive results had been resolved and the test was now giving results which were consistent with those from histopatholical examination, which is considered to be the most reliable standard against which tests such as DELFIA are compared. The test is being applied to samples collected from OTM animals.

Progress on the new study on bovine Milk

Members noted that all previous work, including mouse bioassay, had found no detectable infectivity in milk. Members considered the protocol of further experiments to examine milk for evidence of BSE infectivity. Milk taken from cattle experimentally infected with BSE would be concentrated and examined using a validated diagnostic test. Members agreed that bioassaying samples in cattle or mice would be a more sensitive test for infectivity than current immunologically-based diagnostic techniques, and agreed that such evaluations should be included.

Novel changes in red blood cell progenitors in TSEs

Discussion of this pre-publication paper was deferred because of lack of time.

Internal Committee Items

Previously, SEAC had agreed to hold an open meeting in September 2001. Members briefly considered possible approaches to the meeting. It was agreed to convene a small SEAC working group to consider the arrangements in more detail.

All other Committee items were deferred because of a lack of time.

SEAC
March 2001

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Annex

Summary of recommendations from the SEAC Subgroup: National Scrapie Plan and risk reduction strategies (December 2000)

The National Scrapie Plan

1) The National Scrapie Plan should proceed but with the following modifications:

1. There should be urgent concurrent research to investigate the theoretical possibility that animals that were genetically resistant to developing clinical disease could be latent carriers of infection in neural and non-neural tissues;
2. There should be additional selection against the ARQ allele;
3. The dairy sector should be brought into the programme as quickly as practical;
4. In the absence of evidence of BSE, there should be no move to put the NSP on a compulsory footing, or announcement of any firm intention to do so in the future, until such time that the balance of evidence from research into possible latent carriers clearly supports such a move;
5. Results from such research should be reviewed as soon as it is available;
6. The basis of the scheme should be reviewed after one year in the light of scientific knowledge at that time.

Risk reduction strategies and contingency planning for BSE in sheep

2) The following strategy would provide some degree of assurance for public health if BSE were to be found in a small number of sheep:

1. only permit animals carrying at one least one ARR allele to enter the food chain, and;
2. couple this to an age cut off, perhaps 1 year of age, and;
3. amend current SRM controls to remove intestine from the food chain.

3) The strategy at (2) above should be built into the risk assessment that the FSA are commissioning.

4) The strategy should be considered in terms of its viability in relation to the whole national flock as any contingency plan will need to deal with all sheep flocks.

5) If BSE were found in sheep, sheep and goats should not be used for dairy production, with the exception of ARR homozygous sheep.

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