SEAC: Q & A on their recommendations

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November

Q. SEAC reviewed the Philips Inquiry recommendations on Advisory Committees, what were their conclusion?

A. The key conclusions reached included the need to clarify with Departments the role of SEAC in explaining issues to the public, in giving advice to Ministers and drawing the public’s attention to the lack of knowledge in some areas. It was felt that SEAC needed be more pro-active in identifying problems that might be discussed, rather than relying on Government departments to draw up the agenda. The Committee thought that it needed to be more up to date and open in identifying conflicts of interest and that its advice should relate to scientific aspects and to avoid straying into wider policy areas outside of the remit of the committee.

Q. Has there been any further consideration on the origins of BSE?

A. Yes, Members noted that an the independent scientific assessment of the origin of BSE had been jointly commissioned by the Minister of Agriculture and the Secretary of State for Health against the background of the significant amount of public interest. SEAC considered that it was important to keep an open mind on this matter which would be difficult to resolve unequivocally one way or another.

Q. What was SEAC's advice regarding the National Scrapie Plan?

A. At its meeting in May 2000 Members had agreed that early consideration should be given to a targeted breeding programme to reduce the incidence of scrapie. During the current discussion, however, some concern was expressed that a breeding programme might result in the reduction in the incidence of clinical disease but have little effect on the level of sub clinical infections.

Q. How will SEAC take forward concerns about the National Scrapie Plan?

A. SEAC decided to set up a small sub group urgently to review the evidence on the fundamental principles inherent in the National Scrapie Plan, and on certain detailed aspects of it.

Q. What will the sheep sub-group consider?

A. The SEAC subgroup will consider the premise that genotyping could be used as an aid in genetic selection to reduce the level of infection as measured by the ability to detect the presence of the abnormal prion as well as the level of clinical disease in the sheep flock.

Q. What advice did SEAC give on the potential definition of BSE in sheep, should a case ever be found?

A. The Committee concluded that, from a scientific viewpoint, a single case of apparent BSE would not normally be regarded as a reliable indicator of whether BSE was in the sheep population at the time of sampling. On public health grounds, precautionary action might needed to be taken in such a situation. However it would be desirable for the case to be diagnosed as positive by all of the tests available.

Q. In June 1999 SEAC advised that rendering condensate should not longer be spread on any land. Have there been any further recommendations on this issued?

A. In November members were asked for more detailed advice regarding both treated and untreated rendering condensate and the process of soil injection. SEAC decided that the actual removal of infectivity needed to be examined further before they could support the spreading of treated rendering condensate to agricultural land. SEAC did not see any difference between the risk from surface spreading and soil injection - neither seemed acceptable for untreated condensate. The nature of the material being rendered did, however, significantly change the risk presented by the condensate.

Q. What was SEAC's assessment of the Department of Health's new strategy to improve standards of sterilisation and introduce single use surgical instruments for tonsillectomies?

A. The Committee endorsed the overall risk reduction strategy to reduce the theoretical risk of person-to person transmission of vCJD via surgical instruments. SEAC endorsed the concept of using tonsillectomy as a pilot scheme to see how single-use instruments would work in practice but stressed the need for single-use procedures to encompass other high risk procedures and to improve instrument labelling and tracking. The Committee recommended that monitoring and decontamination procedures should be frequent and extend to both private and military hospitals.

Q. What were SEAC views on the new CJD Incidents panels to assist health authorities and clinicians manage incidents of vCJD?

A. The Committee endorsed this new initiative and noted that the mechanisms being put in place for handling such incidents would need to be able to demonstrate rapid and effective response to incidents as they emerge.

Q SEAC discussed the rising incident of BSE in other European countries. What did it conclude?

A. The Committee expressed concern about the risk resulting from the difficulty of enforcing the Over Thirty Month Rule on imports, and the lack of a consistent application of that rule to all meat and meat products. SEAC suggested conducting a risk assessment in relation to younger animals in countries with rising BSE levels. Finally the Committee noted that a SEAC sub group would be meeting the Chairman of the FSA on 5 December to look at risk issues.

Q. SEAC was briefed on recent BSE modelling projections. What were the findings?

A. Professor Roy Anderson of Imperial College updated SEAC on recent modelling work, not yet published, by his group. They estimate the number of animals entering the food chain in GB within 12 months of developing clinical disease has now fallen to 0.8 animals this year (i.e. "probably less than 1") and 0.5 animals in 2001. It should be noted that specified risk material removal rules would safeguard public health even in those cases.

Q. What was the result of the Committee's regular review of research findings and epidemiological information on vCJD?

A. The Committee was informed that the total number of cases of confirmed and probable cases of vCJD now stood at 87, of which 5 were still alive. Four cases are known to have occurred abroad (1 in Ireland and 3 in France, including 1 probable case). The implications of a case of vCJD in a 74 year old were discussed. These included the possibility that the low autopsy rate among the elderly who have suffered from dementia could mean some cases were not being identified. The Committee were informed of research underway to investigate this, and that further vCJD disease modelling was now in train to allow for a wider age range of cases.

Q. Was there any progress in the Leicestershire vCJD cases?

A. The Committee was updated on the investigation into 5 vCJD cases in a part of Leicestershire. Surveys of local residents had been carried out and a local case control study is underway. A final report is anticipated in March 2001.

September

Q. The FSA have been reviewing BSE controls. What is the latest progress?

A. The draft report of the review was discussed at the last stakeholders meeting on 14 September and subsequently by SEAC on 29 September. Both groups expressed a good degree of general support and agreement for the draft report. Sir John Krebs assured the committee that the final report would take into account technical points raised by SEAC members and other parties. It is envisaged it will then be published and submitted to Health and Agriculture ministers.

Q. What were the Committee’s conclusions on recent work on sub-clinical TSE infection?

A. Recent work demonstrated that mice that were thought not to be susceptible to TSE infection and had not previously shown any clinical signs were capable of replicating prion protein to high levels in their brains. These animals could also transmit disease to other mice. When considering public and animal health measures in light of the experiment SEAC agreed that existing UK measures took account of the possibility that cattle without clinical signs may be incubating the disease. There was some concern expressed about the possible implications of sub-clinical infection in countries where BSE was present but where the control measures were less stringent. However members agreed that the experiment did not raise any public or animal health concerns.

Q. What was the Committee’s conclusions on the transmission of BSE by blood transfusion in sheep?

A. Members noted that the experiment was at an early stage and positive transmission was limited to a single sheep. Therefore further work would be required before the result could be fully interpreted.

On the question of the safety of human blood and blood products, the Committee concluded the measures the Committee had previously advised should be taken on a precautionary basis. They had to a considerable extent anticipated such a finding and the previous recommendation with respect to leucodepletion remained appropriate. The Committee recommended no additional control measures at this time, but noted that it would be important to ascertain the extent to which leucodepletion reduced or eliminated infectivity in the blood of sheep experimentally infected with BSE.

In relation to food safety, the Committee concluded that the finding reported did not present grounds for recommending any changes to the current controls. The Committee considered that the finding did not change their view on bovine products, in the absence of any indication of infectivity in bovine blood, but grounds for additional caution would arise if BSE were ever to be found in commercial sheep.

Q. Does the use of animal products in feed present a risk for the transmission of TSE’s?

A. SEAC confirmed that there was no evidence to suggest the presence of BSE infectivity in cattle blood. The use of dried mammalian blood in animal feed is currently permitted under EU legislation, however the Committee was informed that blood products are rarely used in farm animal feed in the UK and that any bovine blood for animal feed is sourced from animals under thirty months of age. The Committee concluded that whilst intra-species recycling should be discouraged, in the case of dried bovine blood the risks were extremely small and there was no need to change previous advice. However there was a theoretical possibility that if blood meal derived from a sheep infected with scrapie was included in a sheep ration, it could present a risk to animal health and compromise current efforts to eradicate scrapie from the national flock. The Committee recommended that this potential risk and its implications should be considered within the context of the current national scrapie eradication plan.

Q. What about the inclusion of gelatin and tallow in animal feed?

A. Because source material for gelatin and tallow was tightly controlled and subject to processing that would reduce any infectivity present, SEAC was content for these products to remain exempt from the current feed ban.

Q. What are the latest figures for the current incidence of vCJD?

A. The committee was informed that there were now 84 definite and probable cases of vCJD, of which 7 were alive.

Q. Has the committee received a final report on the apparent cluster of vCJD cases in Leicestershire?

A. No. The investigation into the apparent cluster of vCJD cases in Leicestershire is well underway, and likely to report its findings by the end of the year.

Q. Has there been any further consideration of the risk assessment on transmission of sporadic or variant CJD through surgical instruments?

A. Yes. The Committee reconsidered the draft report assessing the theoretical risk of person to person transmission of vCJD from surgical instruments, following up a decision at its meeting in May 2000 to endorse the methodology but to remit some of the draft report’s key assumptions to a Sub-Group for further consideration. SEAC endorsed revisions to the draft report, which took account of conclusions since reached by the sub-group. In particular they endorsed the input value ranges to be used within the modelling on which the report would be based.

In the light of the revised draft report, the Committee revisited its earlier statements on steps it would recommend to reduce the risk of person-to-person transmission. The Committee re-iterated its earlier view that rigorous implementation of washing, decontamination and general hygiene procedures were key steps in reducing any risk and stressed the importance of ensuring that such steps were fully implemented within the health care setting. It further concluded that although the theoretical risk could depend on a number of factors, the theoretical risk it was likely to be greatest from operations involving central nervous system and posterior ophthalmic tissue, followed by lymphoid and anterior ophthalmic tissue. Where discrete surgical procedures can be identified as suitable for single use instruments, for example tonsillectomy, and provided patient safety would not be compromised, the Committee considered that such use should be considered wherever practicable.

Q. Why were the figures on predicted BSE case incidence amended?

A. The figures that were originally presented in the public summary of the November 1999 SEAC meeting did not take account of the estimated effects of the offspring and selective culls. This did not have a significant impact on the majority of the data but did have an effect on the predictions of the number of cases of animals born after mid 1996. Amended figures were presented to the SEAC meeting and incorporated into SEAC’s September 2000 public summary. As a result of this adjustment to the current estimates we expect to see fewer cases of BSE in animals born after mid 1996. To date, only one case of BSE has been confirmed in an animal born after 1 August 1996, the date when further measures to improve feed security were considered to be fully effective. Hence the actual number of cases is currently below the revised predicted level.

Q. Has the committee made any further recommendations for further surveys of TSE’s in sheep?

A. Members agreed that an abattoir survey to monitor the prevalence of scrapie in sheep going into slaughterhouses was of particular importance. Other recommendations included repeating an anonymous postal survey of farmers and conducting a pilot study to assess the viability of a large-scale longitudinal study to establish a baseline for the incidence of scrapie.

Q. What recommendations were made for additional surveillance in cattle?

A. The Committee considered the options for an abattoir survey of cattle brains from animals born after 1 August 1996 to check the effectiveness of the feed ban. Members recommended that a survey should be conducted and that this should begin in August 2001 to ensure that the samples would come from 5 year old cattle, thus coinciding with the peak incidence of clinical BSE. This would optimise the likelihood of picking up animals developing BSE, should there be any.

Q. What were the Committees views on the use of dicalcium phosphate in farm animal feed?

A. SEAC re-examined previous advice from June 1999 and agreed that imported bovine bones and bones from UK cattle under thirty months of age could be used to produce dicalcium phosphate for poultry feed. However, because of concerns about intra-species recycling, Members felt that this practice could only be allowed if it could be guaranteed that the material would not be included in feed for any other livestock. If this could not be guaranteed then it should not be used.

Q. What were SEAC’s views on the proposed risk assessment of small incinerators burning SRM?

A. The Committee agreed to the terms of reference for an independent risk assessment on the potential risks to human health from small incinerators burning SRM but recommended that the scope of the study be widened to include the potential risks to animal health and the incineration of sheep SRM.

Q. Has the Committee made any steps towards making the Committee more open?

A. Yes. SEAC will now publish the agendas from each meeting prior to the release of the public summary and the associated press briefing. Additionally, an open meeting will be held in the coming year.

July

Q. The FSA have been reviewing BSE controls. What is the latest progress?

A. Sir John Krebs indicated that on the basis of the assessment so far, he did not feel that it was likely there would be a recommendation for immediate relaxation of any of the controls in the three areas under consideration-the over thirty months rule, SRM controls and the feed ban. The issue to be considered was more one of identifying at what point in the future it might be appropriate to relax the rules taking account of the EU dimension, progress with science and disease incidence.

Q. What are the latest figures for the current level of incidence of vCJD?

A. The Committee noted that there are now 76 "definite" and "probable" cases, including 7 "probables" still alive.

Q. The number of reported cases appears to be steadily increasing. Is this significant?

A. Yes. The Committee noted that the number of cases reported now indicate a statistically significant rising trend of around 20-30% per annum to date (i.e. currently corresponding to some two to four additional cases each year further to those already being reported) but concluded that it was too early to assess the extent of this trend over the coming years, or forecast accurately the ultimate size of the vCJD epidemic.

Q. There has been a high level of public and media interest in the reports of a number of vCJD cases in an area of Leicestershire. What is the Committee’s opinion on this?

A. The higher number of cases in this area is unlikely to have occurred by chance but this cannot be completely ruled out. SEAC welcomed the fact that a locally based investigation was now underway to look into the circumstances of this apparent cluster, as this could well throw new light on the mode of transmission of vCJD, which would also have implications for our understanding of the national epidemic.

Q. The Committee conducted its regular review of research findings and epidemiological information on BSE. What are the latest findings?

A. So far this year, restricted BSE cases in cattle were 39% lower than during the equivalent period last year. There was encouraging evidence in the figures which was consistent with a significant fall in exposure levels in cattle born in the 1994/96 period compared with cattle born previously. This indicates that the feed ban was increasingly effective over this period.

Q. It has been reported that there has been the first recorded case of BSE in a cow born after 1 August 1996, the date when further measures to improve feed security were considered to be fully effective. What is SEAC’s opinion on this?

A. Members welcomed MAFF’s investigation into the possible routes by which the animal may have been exposed to the BSE agent although they acknowledged it would be difficult to come to definitive conclusions. It had been predicted that a small number of BSE cases would be born after the implementation of further measures assuming the possibility of maternal transmission, although direct exposure to residual contaminated feed could not yet be ruled out in this case. It was agreed that the nature of existing control measures meant that there was no cause for concern with respect to the safety of meat as a result of this case.

Q. Is there any significant risk of person to person transmission of either sporadic or variant CJD which might arise from dental surgery?

A. The Committee concluded that there were no current grounds for recommending changes to procedures involving dentistry, but reiterated the need for thorough cleaning and sterilization practices to be observed in respect of used instruments. In addition, SEAC recommended that further research be undertaken to improve our knowledge, in particular to analyse oral tissues from vCJD patients for any presence of abnormal prion protein.

Q. Has the Committee held to its earlier published view that landfill was an acceptable outlet for MBM of any origin, although it retained a preference for incineration?

A. SEAC reiterated that it had a strong preference for incineration as the favoured route for the disposal of MBM and were uneasy about the use of landfill for the disposal of this material. If there were cases where incineration was not practical the Committee felt it would be preferable for any material going to landfill to be pressure-cooked first or possibly stored above ground prior to incineration.

May

Q. What did the Committee say about the BSE epidemic?

A. The Committee was encouraged by the continuing decline of the BSE epidemic in cattle, particularly the decreasing proportion of four and five year old cattle developing disease. This may indicate increased feed control compliance prior to further feed restrictions in August 1996.

Q. SEAC met the Chairman and Deputy Chair of the new Food Standards Agency (FSA), what did they discuss?

A. Sir John Krebs, the Chairman of FSA, welcomed SEAC's involvement with the new agency and confirmed that the FSA would form part of the joint secretariat of the Committee. Members welcomed the formation of the new Department and agreed to an alteration of the SEAC's terms of reference to incorporate the FSA. SEAC noted that the management of certain TSE research projects relating to food safety had passed from MAFF to the FSA.

Q. The FSA will be reviewing the way risk assessment is used by the Government scientific advisory committees and SEAC will have some input into this. What was the Committee's preliminary view of their role in risk analysis?

A. Members' agreed that their primary role was to advise on the levels of risk, and that it was the role of policy makers to decide how to use that advice in risk management and communication. Members noted that formal analyses of TSE risk are particularly difficult due to the many uncertainties surrounding the subject.

Q. BSE controls are to be reviewed. How will this be conducted?

A. The review would be the responsibility of the FSA with expert advice from SEAC. The Chief Scientific Advisor, Chief Medical Officers in the UK, and the Chief Veterinary Officer would also be involved. Additional input would also be sought from outside experts.

Q. There are European proposals on the removal of specified risk materials (SRM) which would require all EU Members States to remove certain high risk tissue from all cattle and sheep. What is SEAC view on this?

A. The Committee welcomed the proposals and agreed they would represent a significant step forward even though they would require some adjustment to the present UK SRM proposals.

Q. What adjustments would be necessary?

A. In relation to cattle, Members noted that the Commission proposal would result in the removal of intestine and thymus from cattle over 6 months old rather than from all cattle as is currently the case in the UK. SEAC felt that the change in relation to cattle intestine might represent an increased risk, although this was likely to be extremely small.

With sheep, Members agreed that it would be preferably to continue to remove whole heads rather than, as proposed by the Commission, the skull including brain and eyes, and from all sheep rather than those over 1 year old. They noted though, that sheep SRM removal was based on theoretical possibility that BSE may have passed to sheep and current measures were based on a risk reduction not a risk elimination strategy.

On balance, the Committee felt that the benefits of introducing controls on SRM across the European Union would outweigh the slight increased risk that may arise from any consequential change to the UK's existing controls.

Q. What are the Committee's views on MAFF's initial ideas for reducing scrapie within the national flock?

A. Members agreed that improved understanding of the genetics involved in disease susceptibility could be exploited to devise intervention strategies to reduce the prevalence of the disease. Early consideration should be given to a targeted breeding programme in conjunction with suitable disease accreditation schemes.

Q. What is SEAC's opinion on the draft report assessing the theoretical risk of person to person transmission of vCJD from surgical instruments?

A. The Committee endorsed the modelling on which the report was based, but concluded that the input value assumptions, which reflected estimates of relative levels of pre-clinical infectivity theoretically possible within various body tissues, needed further consideration. A sub-group will be set up to look again at these key assumptions.

Q. Have the Committee agreed to commission a risk assessment on BSE in sheep?

A. Yes. A risk assessment will be commissioned to quantify the risk to public health if BSE was found in sheep. A SEAC sub group will be convened to guide the process.

February

Q. Have SEAC considered the recent publication in ‘Transfusion’, which suggested that infectivity was detectable after disease onset in the plasma of mice experimentally challenged with a mouse adapted human TSE?

A. Yes they have. The Committee concluded that priority should be given to carrying out a study on mice infected with a mouse adapted BSE agent at various stages before development of disease. However, the Committee did not recommend any measures in addition to those already in place to reduce any potential risk to public health from human blood and blood products.

Q. What did SEAC note about the outcome of the recent meeting of the Epidemiology Sub-Group on 09 February?

A. On the definitions used for ‘confirmed’ and ‘probable’ vCJD, SEAC endorsed the view of the Sub-Group that robust scientific criteria now existed. These definitions would enable live ‘probable’ cases to be separately identified for the first time and could then be included within the data on vCJD published by the Department of Health.

Q. What did SEAC say about work to ascertain the sub-clinical prevalence of vCJD in the human population?

A. SEAC recommended that this work should be taken forward with all possible speed. This might include large scale surveys taking tonsils and appendix tissue for evidence of infection.

Q. The Committee noted that the pathogenesis of the disease caused by BSE in mice was different to the pathogenesis of BSE in cattle but more similar to that of TSE’s in sheep and humans. Were there any implications for the safety of the food chain?

A. No. Given the difference in the pathogenesis of the disease in cattle and the mouse model, and taking account of the results of bioassays of cattle tissues in both mice and cattle, there were no further implications for the safety of the food chain.

Q. What did SEAC note from their review of key research related to scrapie and BSE in sheep?

A. Members felt that preliminary and interim results of studies of experimental BSE pathogenesis in sheep tend to support SEAC’s previous conclusions that BSE in sheep is likely to behave in a very similar way to scrapie. The latest work on the pathogenesis of scrapie confirms earlier findings that the disease appears to infect peripheral tissues including lymph nodes, spleen and parts of the intestine as well as the central nervous system. It indicates that the spread of infection is likely to be from the gut via peripheral nerves or via innervations of the lymphatics to the central nervous system.

Q. Have there been any results of the agent strain typing on isolates from sheep brains with natural scrapie?

A. Although incomplete, over 30 isolates are advanced enough to suggest that they do not have the characteristics associated with the BSE agent. The Committee agreed that further work needed to be done on screening sheep for evidence of infection with the BSE agent but concluded that there was no need for further health controls.

Q. There is an EU proposal on specified risk materials which would classify individual Member States according to the incidence of BSE in cattle. What is SEAC’s view on this?

A. Members noted that to set out SRM controls for sheep and goats on this basis would not be consistent with the likely routes of exposure of sheep to BSE infection. This is because the risk of exposure would vary according to feed practices assuming that sheep had in fact been infected from feed. It would also depend on if, and how infection and disease associated with the BSE agent could be propagated in sheep.

They further agreed that, in the event that the EU proposal to add intestine to the list of SRMs from sheep or goats were adopted by Member States, they would not advise against this but would advise that the whole intestine from sheep of all ages should be classified as SRM.

Q. What is the Committee’s opinion on the proposal by MAFF to extend the survey of the brains of cattle in the Over Thirty Months Scheme in the next year?

A. SEAC felt it was important to continue this work as it provided an independent check on models of the progress of the BSE epidemic. The performance of diagnostic tests was seen as critical to the outcome of such surveys.

Other years: [2002] [2001] [1999] [1998] [1997] [1996/1997] [1996]

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Page last updated: 09 April 2002