Public summary of the meeting on
3rd June 1999

The Spongiform Encephalopathy Advisory Committee (SEAC) met at the offices of the Ministry of Agriculture, Fisheries and Food, Tolworth on 3 June 1999. This was Sir John Pattison’s last meeting as Chairman before taking up his new appointment as Director of Research and Development at the Department of Health in early September. Dr James Ironside of the CJD Surveillance Unit in Edinburgh also attended his first meeting as a full member following his recent appointment to the Committee.

SEAC conducted its regular review of research findings and epidemiological information on BSE and vCJD. It noted that the total number of vCJD cases in the UK was 40 (since the meeting a further case has been confirmed). Although, at the time of the meeting, there had been only one confirmed case in 1999, a number of suspect cases were being investigated. It was too early to draw any conclusions as to whether or not the increase seen in the last quarter of 1998 would be sustained.

The Committee was also informed that in view of recent press speculation about the possible link of vCJD to childhood vaccines, the CJD Surveillance Unit had undertaken an analysis of cases by year of birth. The Committee noted the conclusion that it is 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.

A report was also received on work being undertaken by the CJD Surveillance Unit and workers in other European countries to develop clinical criteria for the diagnosis of probable cases of vCJD. Once these had been agreed they would form the basis of published statistics on the number of probable cases. Some suggestions for additions to the criteria were made, including the possible use of tonsil biopsy.

The number of cases of BSE continues to decline, albeit at a lesser rate than in previous years. The likely explanation is that the decline in 1996 and 1997 was more pronounced as a result of the culling of certain birth cohorts. A progress report was given on the preparation of revised predictions on the future of the epidemic and on the preparation of other information required for a review of the over-thirty-month scheme. These were expected to be available in time for a substantive discussion of the issues at the Committee’s next meeting in September.

Preliminary results of the scrapie postal survey, and possible follow up action, were considered. The level of response to the questionnaire had been encouraging and a paper is being prepared for publication in a peer reviewed journal. The Committee then went on to emphasise the priority of analysing sheep brains for evidence of prion disease as rapidly as possible.

The Committee had been asked to consider a number of papers dealing with possible relaxations in the existing controls on farm-animal feeds. It could not at present see any scientific justification for change in the current controls, and was concerned about the potential enforcement implications which could arise if any changes were made. It therefore recommended that:

  • 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; and

  • a recent change to the EU ban on mammalian protein in ruminant feed, which would allow hydrolysed 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.

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The Committee also clarified its earlier advice (November 1998) by confirming that rendering condensate should no longer be spread on any land, and not just those fields where cattle might graze.

Following delays in arranging facilities for the incineration of stored stocks of OTMS meat and bone meal, SEAC’s advice had been sought on the suitability of landfill as a possible supplementary disposal option. SEAC concluded that there was no recent scientific evidence which called into question their earlier view, in 1996, that landfill is an acceptable outlet for MBM of any origin, although SEAC’s preference for incineration remains. The Committee recalled that it had given its opinion on the range of assumptions to be included in risk assessments commissioned by the Environment Agency in 1997, one of which led to the conclusion that landfill had been a suitable option for the past practice of disposing of some BSE suspects by this method. The Committee agreed that a further risk assessment on disposal of OTMS MBM in landfill sites should be undertaken.

At the request of the Department of Health, the Committee considered the possible risk of transmission of vCJD through the re-use of trial contact lenses on subsequent patients. Scientific data relevant to the issue are limited. Any potential risk is probably very low, but 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.

An update was also given on work to follow up the recommendations made at previous meetings aimed at reducing the potential risk of vCJD transmission associated with surgery. The Committee noted that various aspects of the issue are under consideration and requested for its next meeting, a full report on what had been achieved, with the identification of any constraints on progress.

The next meeting of the Committee will be held on 20 September 1999.

SEAC
June 1999