SEAC: Q & A on their recommendations

1999

November

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

A. The Committee noted that the total number of people who had died of vCJD now stood at 48. It remained too soon to make predictions with any confidence about the likely number of deaths in the coming years.

Q. What are the latest recommendations from the Advisory Committee on Dangerous Pathogens (ACDP)/ SEAC Joint Working Group (JWG) on the work on the safe working with TSE agents?

A. The JWG recommended that recipients of corneal transplants should be added to the list of those patients for whom special precautionary measures would be necessary in a health care setting, to prevent any risk of person to person transmission of TSE infection. SEAC endorsed the JWG’s recommendation.

Q. What are the Committee’s comments on the latest estimates from Scientists at Oxford University of the numbers of cases in the BSE epidemic from 1996 to 2001?

A. The epidemic is still in rapid decline but will have a long tail. SEAC noted that the predictions had been revised upwards from the predictions made in 1996 but had much narrower confidence bands than previous estimates for the same period. However, they still fell within the confidence bands of the earlier analysis.

Q. Why have predictions been revised upwards?

A. The predictions are higher because the estimated risk from exposure did not decline as rapidly as projected in the earlier analysis. The likely explanation for this is that cattle were exposed to feed which was accidentally cross-contaminated with BSE infected meat and bone meal destined for pigs and poultry.

Q. The Committee reviewed the Over Thirty Month (OTM) rule. What were their conclusions?

A. The Committee agreed that the OTM rule had been the key measure put in place to protect public health in 1996, by significantly limiting the number of infected animals which might otherwise enter the food chain. SEAC concluded that modifying the rule to increase the age of animals permitted to be slaughtered for human consumption would be premature. Furthermore, they recommended that the controls currently in place should continue to be rigorously enforced.

Q. What were the Committee’s conclusions regarding the possible use of meat and bone meal derived from pigs for inclusion in poultry feeds?

A. SEAC considered that a relaxation of the feed ban in the UK could not be supported on scientific grounds. The principal concern remained that the recycling of animal-derived proteins within or between species, via feed, represented a potential risk of the development of TSE infection in livestock.

Q. SEAC considered a proposal for a study of offspring of BSE cases to measure the rate of maternal transmission of BSE in cattle. What were their conclusions?

A. The Committee agreed that the offspring were valuable animals for study but given the revised predictions of the decline of the BSE epidemic and the long term nature of the experiment, they did not think that the study would yield results within a useful time frame and did not consider it high priority.

September

Q. What did the further analyses by the CJD Surveillance Unit of the geographical distribution of vCJD tell SEAC?

A. The results confirmed earlier analyses that there was no evidence of any geographical clustering of cases.

Q. What further advice did SEAC give the Department of Health regarding trial or diagnostic contact lens fitting sets and ophthalmic devices?

A. The Committee recommended that trial or diagnostic lens fitting sets should be confined to single patient use. They also recommended that the components of ophthalmic devices that touch the cornea should be for single patient use, wherever practicable.

Q. The Committee reviewed the action being taken in the U.K to reduce the theoretical risk of transmitting vCJD through blood & blood products. What were there conclusions?

A. SEAC were pleased to note that all licensed blood products are now manufactured using non-U.K plasma, and all blood collected in the U.K will be leucodepleted from 1/11/99. The Committee concluded that no further steps were currently necessary to ensure the safety of UK blood.

Q. What were the Committee's views on the action being taken by Department of health to reduce the risks of iatrogenic transmission of vCJD through surgical procedures?

A. SEAC confirmed its views that rigorous implementation of washing, decontamination and general hygiene procedures are key measures in minimising the risk of infection.

Q. What did SEAC conclude about the theoretical risks of iatrogenic transmission?

A. The Committee noted that although the theoretical risk of iatrogenic transmission could depend on a number of factors, it was likely to be greatest from operations involving the central nervous system, ophthalmic tissue and lymphoid tissue. The committee considered that wherever practicable the use of disposable instruments for such surgery was to be encouraged and noted that Department of Health were examining the feasibility of the use of disposable tonsillectomy instruments.

June

Q. As a result of recent speculation of a link between vCJD and childhood vaccines, the CJD Surveillance Unit conducted an analysis of cases of vCJD by year of birth. What were SEAC’s views on the conclusion of the analysis?

A. SEAC noted that it was unlikely that the cases of vCJD to date would have been exposed to BSE infectivity through the vaccines needed to immunise them as young children, since the vaccines would have been produced well before the BSE epidemic.

Q. What are the future plans for the publication of statistics of probable cases of vCJD?

A. Work is being undertaken at the CJD Unit and in Europe to develop clinical criteria for the diagnosis of probable cases of vCJD, which will form the basis for published statistics on the number of probable cases. SEAC have made suggestions for additions to the criteria, including the possible use of tonsil biopsy.

Q. What is the likely explanation for the slower rate of the decline in the recent numbers of BSE cases as opposed to previous years?

A. The likely explanation is that the decline in 1996 and 1997 was more pronounced as a result of the culling of certain birth cohorts.

Q. SEAC considered the possible relaxation of existing controls on farm-animal feeds, what were their recommendations?

A. SEAC recommended that there should not be any change to existing controls. The following recommendations were made:

the ban on feeding mammalian meat and bone meal to livestock should not be lifted, in whole, or in part.

UK-derived bones should not be used to produce calcium phosphate for farm animal Feed

the recent change to the EU ban on mammalian protein in ruminant feed, which would allow hydrolised protein to be fed to ruminants, should not be adopted, since complete hydrolysis could not be constantly ensured and portions of the prion molecule might still be infectious.

Q. In November 1998 the Committee looked at the risk of spreading rendering condensate and advised that it should be prohibited on fields where cattle might graze, has there been any change to that advise?

A. The committee clarified its earlier advice by confirming that rendering condensate should no longer be spread on any land, and not just those fields where cattle might graze.

Q. What was SEAC’s advice on the use of landfill as a possible supplementary disposal option for stored stocks of OTMS meat and bonemeal?

SEAC had previously considered the landfill option in 1996, and had concluded at that time that it was an acceptable outlet for MBM of any origin. The Committee felt that there was no recent scientific evidence to question their earlier view. However SEAC’s preference for incineration remains. The Committee agreed that a further risk assessment on disposal of OTMS MBM in landfill sites should be undertaken.

Q. SEAC considered the possible risk of transmission of vCJD through the re-use of trial contact lenses on subsequent patients, what were their conclusions?

A. Scientific data relevant to the issue are limited, but any potential risk is considered to be very low. However, the Committee felt strongly that the Department of Health should encourage opticians to adopt, as a matter of best practice, the single use of trial lenses followed by safe disposal.

Q. What did SEAC say about the preliminary results of the scrapie postal survey?

A. SEAC considered the results of the scrapie postal survey, and possible follow up action. The level of response to the questionnaire was encouraging, and a paper was being prepared for publication in a peer reviewed journal.

The Committee emphasised the priority of analysing sheep brains for evidence of prion disease as rapidly as possible.

March

Q. At their meeting in March 1999 the Committee received a presentation on the risk assessment model of vCJD transmission via surgical instruments developed by Department of Health. What did they say about this?

A. The Committee commended the usefulness of the model which will allow the effects of new information and possible risk reduction measures to be assessed rapidly.

Q. What did SEAC say about the recommendations from the Advisory Committee on Dangerous Pathogens/SEAC Joint TSE Working Group and its sub-group on surgical instruments?

A. SEAC fully endorsed the sub-group recommendations for further urgent work on the decontamination of surgical instruments and diagnostic equipment to reduce the risk of prion contamination. In the meantime SEAC recommended that discussions with surgeons and the Medical Devices Agency on the greater use of disposable instruments for certain surgical procedures should continue.

Q. At its March 1999 meeting the Committee reviewed progress in dealing with the BSE epidemic and the measures in place to protect public health. What did they say?

A. SEAC noted that the ban on the sale of beef for human consumption from cattle over 30 months of age could in due course be amended. It agreed that any change to the Beef Assurance Scheme age limit or eligibility criteria should be addressed as part of any such review. The Committee concluded that further information and analysis would be needed to inform any decision and asked the Secretariat to set this work in hand for the next meeting. The Committee confirmed that this was an issue which would require careful consideration and that it could take several meetings to develop its advice. In the meantime it recognised the public interest in this area and would support and wish to be involved in any MAFF initiatives to encourage public discussion of the issues involved.

Q. What did SEAC say about the link between vCJD and BSE in March 1999?

A. The Committee reviewed its public statement on the link between vCJD and BSE originally made in March 1996. It noted that further research had shown that BSE and vCJD were caused by a similar prion strain and concluded that vCJD was an acquired prion disease caused by exposure to BSE or a BSE like agent. When the Committee made its original statement about the first 10 cases in March 1996 it referred to exposure before the SBO ban. After discussion the Committee recognised that not all new cases would necessarily relate to exposure before this ban.

January

Q. What is Pentosan Polysulphate?

A. Pentosan Polysulphate (PS) is a member of a group of complex compounds, a number of which have been shown to have an effect on the natural history of scrapie in experimental animal models. The limited experimental evidence suggests the effects are likely to vary according to both the strain of the TSE agent and the species of the host. Therefore, it is difficult to extrapolate the results of the scrapie studies in rodents to assess the likely effect of early treatment with this group of compounds on the natural history of vCJD in humans.

Q. What advice did SEAC give to Ministers regarding the possible use of Pentosan Polysulphate as a prophylactic against vCJD?

A. The Committee agreed that there was some scientific evidence that compounds in the Pentosan Polysulphate (PS) group had been observed to have an effect on the replications of the scrapie agent and therefore might have potential for use as a prophylactic agent against vCJD in humans. However, efficacy data were limited and were restricted to animal models using selected strains of the scrapie agent and their applicability to BSE or vCJD was unknown. Safety data currently available on the human use of PS is also restricted to about 10,000 patients treated for unrelated conditions.

Further research should be carried out, ideally using BSE and vCJD in experimental animal models, such as transgenic mice carrying the human PrP gene, that may give a better indication of the likely effects of Pentosan Polysulphate in humans. In addition, since the peripheral pathogenesis of TSE infection in mice might be significantly different to that in man, studies in primates should also be considered.

Further consideration of the use and safety of PS will need to be given by the Committee on the Safety of Medicines(CSM) and SEAC welcomed the setting up of a CSM sub-group that will involve SEAC Members to take this forward. In the absence of further data on efficacy and safety, SEAC did not consider that it was justified to recommend the wide use of Pentosan as a possible prophylactic against vCJD.

Q. What did the Committee say about cheek meat at their meeting in January 1999?

A. The Committee was asked by the Chief Medical Officer of England to consider the risk associated with cheek meat for human consumption removed in Northern Ireland from bovine heads imported from the Republic of Ireland. They noted that a decision of the courts in Northern Ireland meant that the importation of such bovine heads by one specific company for the removal of cheek meat for human consumption had now been permitted pending the outcome of an appeal against this decision to the European Court of Justice.

The Committee considered that it would be preferable that cheek meat imported into the United Kingdom came only from animals from countries which have no cases of BSE and that bovine heads from which cheek meat was removed within the borders of the UK also came only from such countries. However, SEAC recognised that imports are controlled by EU law. With respect to UK cattle over six months old SEAC reaffirmed its advice that the whole head, other than the tongue, should continue to be treated as specified risk material (SRM).

Q. What did SEAC say about the report from Det Norske Veritas (DNV) on the Assessment of the Risk of Exposure to vCJD Infectivity in Blood and Blood Products?

A. The Committee agreed that because of the many uncertainties preparation of the Report had been a demanding task for DNV and it was difficult to draw any clear conclusions. The Report provided a great deal of useful background information on the sourcing, processing and use of human blood and blood products. The Committee welcomed the intention to publish the Report and saw no reason to revise its earlier precautionary advice to Ministers recommending leucodepletion of blood destined for transfusion.

Q. What were the Committee’s comments on the proposal for an overall framework for the handling of risk analysis, risk management and risk communication across a range of food and food safety issues?

A. SEAC, like other food safety Advisory Committees, had been asked for comments on the proposal for such a framework but at their January (1999) meeting they decided to postpone further discussion until after the BSE Inquiry had reported so that its findings could be taken into account.

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