SEAC : Statement - 24th March 1996

Statement

- 24th March 1996

Introduction

The Committee has reported 10 cases of a previously unrecognised variant of CJD. It agreed this weekend, after further discussion and consideration of additional genetic data from some of these patients, that its conclusions of 20 March 1996 are unchanged. That is, on current data and in the absence of any credible alternative, the most likely explanation at present is that these cases are linked to exposure to BSE before the introduction of the SBO ban in 1989. It emphasises that there are only 10 cases to date, and that it is not in a position to confirm whether or not there is a causal link between BSE and the human disease.

Risk assessment

The Committee has carefully considered whether a quantitative risk assessment can provide an estimate of the absolute risk in relation to BSE. In its judgement a precise measure is impossible because of a number of interacting uncertainties, including:

the magnitude of the species barrier between cattle and man;
lack of data on levels of infectivity in a range of important cattle tissues which are below the level of detectability by current assays;
the uneven distribution of infectivity in any tissue;
the time course for the appearance of infectivity over the duration of the incubation period;
whether there is a dose below which there is no risk of infection.

It therefore made assessments on the basis of the available quantitative data, and where these were lacking on expert opinion and its own collective judgement.

Age-related susceptibility

SEAC has been asked to give further advice on the risk to children. It first considered whether susceptibility is likely to be age-related. It had a wide ranging discussion of the changes in the physiology of the human gastro-intestinal tract and host defences throughout life. It was assisted in these discussions by three leading experts covering the fields of paediatrics, gastro-enterology, infection and immunity. It considered carefully its knowledge of the transmissible spongiform encephalopathies (kuru,CJD,scrapie,transmissible mink encephalopathy, BSE) in natural infections and animal model systems. If the new variant of CJD is related to exposure to BSE, this exposure is likely to have been between 1982 and late 1989, and the age range of the cases does not suggest that those who were children at that time were at any greater risk than young adults. Taking all the above into account it concludes that if human infection with the BSE agent occurs, infants and children are not likely to be more susceptible to that infection than are adults.

It is not clear why no cases of this previously unrecognised variant have been found in older patients. This could be due to different age-related dietary habits, to reduced susceptibility in this group, or to the unrecognised occurrence of this variant of the disease in older age groups especially those in which dementia is more prevalent.

Other vulnerable groups

The Committee also considered the following groups: - the immunosuppressed, patients in hospital and pregnant women. It concludes that, in its judgement, if human infection with the BSE agent occurs, none of these groups is likely to have any increased susceptibility to infection.

Public, the younger generation, and parental concerns

The Committee is aware that the public want to be reassured, most especially about the risks to the younger generation. Parents are naturally concerned about the risks to their own children. No human activity is without some risk; if the Government rigorously enforces the current and newly recommended controls the Committee believes that this risk is likely to be extremely small; however the Committee recognises that parents will often choose to reduce risk to their children beyond that which they are prepared to accept for themselves.

It is important to be aware that many foods are associated with health risks, and that changing from beef to non-beef products is not necessarily without risk.

Trimmings from cattle over 30 months of age

The Committee reconfirmed its recommendation that cattle aged over 30 months must be deboned in licensed plants, and went on to recommend that the trimmings, comprising the obvious nervous and lymphatic tissue (including the 14 lymph nodes specified in EC trade legislation) and the vertebral column (excluding tail vertebrae) should be treated as specified bovine offal. Other bones do not need to be treated as SBO if they can be separated from the vertebral column, without cross contamination.

It also recommended that the whole head of animals aged over 6 months of age, except for the tongue (provided that it is removed without contamination), should be treated as specified bovine offal.

The Committee asked Government to ensure that the relevant authorities have the necessary statutory authority to enforce fully these recommendations and the existing provisions.

Gelatin

The Committee reviewed the use of gelatin produced from non-SBO bovine material with the assistance of an expert from the Medicines Control Agency (MCA). It concluded that this material was safe for use in pharmaceutical and medical devices as well as food, given the large reduction in theoretical infectivity in the production of gelatin. It noted that the MCA will be reviewing the use of gelatin and tallow on 1 May 1996.

Meat and bone meal (MBM)

The Committee confirmed its previous advice that the use of mammalian meat and bone meal should be prohibited in any circumstances where there might be a risk of the material being fed to or ingested by ruminants. In particular, it must not be incorporated into any feed for any farmed animals, including fish or horses, or into fertiliser likely to be used on land to which ruminants have access.

Advice

The Committee therefore advise the Government:-

to ensure that all the restrictions previously recommended, those of 20 March 1996 and in this document are fully implemented and sustained. If this is ensured, any BSE related risk from eating any beef or beef products is likely to be extremely small.
to reinforce immediately the surveillance of CJD and associated epidemiological research, commensurate with the emerging medical, social and economic importance of this disease;
that these issues will require long term, basic and applied research. Both the immediate and the long term research needs will require substantial additional resources. It is important that there should be no delays due to difficulties in obtaining resources.

The Committee does not believe that additional measures are justified at this stage, but the situation needs to be kept under careful review so that additional significant information can be taken into account as soon as it becomes available