Volume 11: Scientists after Southwood
4. The Spongiform Encephalopathy Advisory Committee (SEAC)
Deliberations and advice
1. Advice on the safety of beef

4.92 From 1 May 1990 until 20 March 1996, SEAC was the principal advisory committee to which the Government looked for advice on a range of matters relating to TSEs. SEAC held 28 meetings over the period. In quieter years, the Committee would meet only two or three times. However, in other years, the Committee met regularly every two months or so and in exceptional circumstances emergency meetings were called to discuss matters of immediate importance. SEAC continues to advise the Government on BSE to this day. A chronological table of SEAC's meetings and the topics discussed can be found at Annex 2 of this volume.

4.93 Where SEAC's advice impacted on policy decisions that were taken, this is described in the relevant narrative volumes (5, 6 and 7). In this volume we set out, under different topics, an account of the major matters on which SEAC gave advice. In respect of each topic, we follow SEAC's involvement in a chronological order, including details of relevant background events where we consider this helpful.

1. Advice on the safety of beef

4.94 MAFF and DH specifically asked SEAC for advice about the safety of beef several times between May 1990 and March 1996. Here we look at the first occasion on which SEAC were asked to give such advice and the manner in which that advice was formulated during the period from May to July 1990. Other occasions on which SEAC were asked to advise on the safety of beef are adequately covered in vol. 6: Human Health, 1989-96.

SEAC's advice

4.95 On 24 July 1990, SEAC provided the CMO with its considered advice on the safety of beef in a letter and accompanying annex entitled 'The epidemic of BSE and the public health implications of eating beef'. ¹ The letter stated:

OPINION ON THE PUBLIC HEALTH IMPLICATIONS OF EATING BEEF AND THE EPIDEMIC OF BSE

1. The Spongiform Encephalopathy Advisory Committee having reviewed the evidence available have concluded that British beef can be eaten safely. The rationale for this view is as follows.

2. Bovine Spongiform Encephalopathy (BSE) appears to be closely similar to scrapie since:

(i) the disease induced in mice with material from BSE animals is like scrapie in mice;

(ii) the disease behaves clinically and neuropathologically in cattle like scrapie does in sheep;

(iii) the origin appears to be scrapie-infected feedstuffs.

3. Therefore we would expect that the causal agent of BSE is like the agent causing scrapie in sheep namely:

(i) that the agent will be present in spleen and similar tissues, and in brain; and

(ii) that in meat the agent will not be present or if present will be at such low levels that it will be undetectable by the most sensitive method.

We note that so far the results of experiments with the BSE agent are consistent with these assumptions.

4. The epidemiological evidence of a lack of association between scrapie and human disease appears to us to be secure. Therefore if BSE is exactly like scrapie, oral transmission (and any form of natural exposure) should not represent a hazard to man. Because the possibility that the agent might have changed cannot be dismissed, we agree that the measures that have already been taken in response to BSE in cattle are appropriate, although we do not believe on present evidence that any similar measures are necessary in the case of scrapie in sheep.

5. Oral transmission of some spongiform encephalopathies undoubtedly occurs - although very large doses are needed because the oral route is very much less efficient than, say, intracerebral inoculation.

6. In summary, therefore, protection for humans against oral infection with BSE is afforded by the cumulative effect of the following factors:

(i) the agent is likely to be similar to scrapie and there is no evidence that scrapie agent is hazardous for man;

(ii) the oral route of transmission is very inefficient;

(iii) sick animals are destroyed;

(iv) those offals likely to contain the highest amounts of infective agent in any subclinical cases are removed from human consumption. This is now required by law;

(v) cooking would reduce any remaining infectivity further.

7. In our judgement any risk as a result of eating beef or beef products is minute. Thus we believe there is no scientific justification for not eating British beef and that it can be eaten by everyone.

8. We propose to keep the matter under review as additional evidence becomes available. We have provided in an annex an expanded version of this opinion. ²

4.96 We note the following passages from the annex attached to SEAC's letter:

1. Summary

. . .

1.2 Parallels with scrapie and other spongiform encephalopathies suggest the 'dose' of BSE agent if it is indeed present in food as consumed will be so small as to be undetectable by the most sensitive known method for these agents, namely bioassay by intracerebral inoculation into mice. In addition we consider that the oral route of transmission is so inefficient that there is a huge safety margin. There are no reasons to expect specially sensitive subpopulations. The strong probability is that BSE, like scrapie, is no hazard for humans in any event, although the possibility of a modification to the agent cannot be excluded.

1.3 In our judgement, any theoretical 'BSE risk' in British beef is so remote that for practical purposes it can be ignored. So this is entirely consistent with the view that British beef can be eaten safely by everyone, both adults and children . . .

4. BSE agent in human food

All cattle showing signs suggestive of BSE are slaughtered and destroyed [16]. All the evidence suggests that very few symptomatic cattle are being detected at slaughterhouses [17] and those that are, do not enter any food chain. On the scrapie model, it is cattle with symptoms which may be expected to have the highest levels of agent in the central nervous system and also high levels in the lymphoreticular system.

Since 13 November 1989 in England and Wales, and from 30 January 1990 in Scotland and Northern Ireland, various bovine offals have been prohibited for human consumption from all bovines over 6 months of age [18]. These offals are the brain, spinal cord, spleen, tonsil, thymus and intestines and are those which could harbour the BSE agent in subclinically infected animals that are apparently healthy . . . In practice, these offals have been used little for human consumption in the UK. Calves under 6 months are exempt: none of these animals will have been fed on meat and bone meal but even were infection possible, say through maternal transmission, based on the scrapie experience [10] . . . the infective agent would not be present in detectable quantities at that age. As a result of these actions taken very little BSE agent is expected to remain in the parts of the bovine carcase available for human consumption. Because of dilution of tissues that might contain small amounts of agent by meat containing none, even in meals from these animals the infectivity is unlikely to be detectable, even by intracerebral mouse inoculation.

The vast majority of animals reaching slaughterhouses at present will not be infected with the BSE agent. Indeed, if BSE is not transmitted maternally and the feed regulations introduced in July 1988 [16] have been effective, and as the majority of cattle being slaughtered are under 24 months of age, only a tiny minority of cattle destined for human consumption are old enough to have been exposed to BSE infection . . .

5. The oral route of infection

5.1 The oral route is clearly capable of transmitting spongiform encephalopathies in the diseases of BSE and transmissible mink encephalopathy (TME), and it is assumed to be an important natural route of transmission in scrapie and kuru.

5.2 Experimental studies, however, show ingestion to be very inefficient, at least 5 orders of magnitude less efficient than intracerebral injection [Kimberlin and Walker (1989) Virus Research 12, pp. 201-12]. In the transmission work done to date with BSE, the incubation period in mice was longer after a large oral dose of BSE-infected cattle brain than after much smaller parenteral injections [Fraser et al. (1988) Veterinary Record, 123, p. 472 and Barlow and Middleton (1990) Veterinary Record 126, pp 111-12]. In these, as in other animal experiments, large doses, far in excess of what would be experienced in nature, appear to be needed for successful disease transmission.

5.3 It is concluded that the occasional low doses of BSE agent in human food are well below those capable of infecting humans, even if humans were specially susceptible to the agent.

6. The species barrier

. . .

6.5 If BSE, like scrapie, presents no hazard for man, there are no public health implications from this new disease. Section 2 above describes how close BSE appears to be to scrapie. The epidemiology strongly suggests that it was not a change in scrapie's pathogenicity that led to infection in cattle, [Wilesmith et al. (1988) Veterinary Record, 123, pp. 638-44.] However, changes, sometimes permanent, can occur as a result of passage through a different species [Kimberlin et al. (1987) Journal of General Virology, 68, pp. 1875-81] and the agent to which humans are now exposed may behave differently from scrapie. Nevertheless, it is reassuring that most of the evidence to date . . . emphasises the similarities between BSE and scrapie. We do not yet know if the recent description of spongiform encephalopathy in a cat [Wyatt et al. (1990) Veterinary Record, 126, p. 513] indicates transfer of scrapie or BSE to a new species or whether this is a feline disorder in its own right. In our view, this cat case does not increase the likelihood of BSE transmission to humans . . .

7. Risk assessment

7.1 To assess the human risk from BSE we have to take into account the low frequency with which infected animals may reach the abattoir (see 4.3 above) and the small chance of any infective agent being present in meat passed as fit for human consumption (see 4.2 above). In addition, very high doses are needed for successful transmission by the oral route (see 5.2 above) and there is probably at least a partial species barrier to human infection with BSE . . . Thus if there is indeed a human hazard then the risk to humans from BSE in beef must be very small indeed. In our judgement if there is any risk it is negligible . . .

7.4 Our own judgement based on our assessment of the available scientific evidence is that the BSE risk, if there is one, is so slight that it can be ignored. We hope our scientific opinion will help others to make their own decisions, whether personal or national. This will depend on their viewpoint, the weight they give to our opinion and the view they take of what risks they are prepared to accept and what they are prepared to pay for. For our own part and as we discussed with the Chief Medical Officer before he made his statement on 16 May 1990, 'there is no scientific justification for not eating British beef. We have no hesitation in saying that beef can be eaten safely by everyone, both adults and children'. ³

The genesis of the advice

4.97 In May 1990, following the announcement that a cat had contracted a BSE-like disease, ⁴ the Government came under immediate pressure to issue a statement on beef. Upon learning of the identification of what appeared to be an SE in a cat, Sir Donald Acheson gave instructions for an emergency meeting of SEAC to be called as soon as possible. In his statement to the Inquiry, he noted that the first practicable date was 17 May, and said that: 'It was my earnest hope that I would not have to make a public statement on the significance of the case of FSE before having the advantage of the advice of SEAC on that date.' ⁵

4.98 In the event the pressure was such that Sir Donald felt he had to respond before the SEAC meeting. The circumstances in which he did so are described in vol. 6: Human Health, 1989-96. Following a meeting with Dr Tyrrell and Dr Pickles and telephone calls with Dr Will and Dr Kimberlin, Sir Donald issued a press release on 16 May 1990, which stated:

I have taken advice from the leading scientific and medical experts in this field. I have checked with them again today. They have consistently advised me in the past that there is no scientific justification for not eating British beef and this continues to be their advice. I therefore have no hesitation in saying that beef can be eaten safely by everyone, both adults and children, including patients in hospital. ⁶

4.99 On 17 May 1990, SEAC held its emergency meeting. In his statement, Dr Tyrrell noted the purpose of the meeting 'was in part to amplify the advice given previously on the safety of beef'. ⁷ The minutes record that this amplification was to form the basis of a letter to the CMO, 'from which he could quote in further advice to the medical profession'. ⁸ The minutes record the following:

In considering the remote risk to humans, the possibility of susceptible sub-populations was discussed. The pregnant and immunodeficient were not thought relevant. The young were not thought particularly susceptible either, although as the Southwood Committee commented there were suggestions in some quarters that they might have increased infection, but the effect of differential exposure was confounding and evidence from some species contradictory.

In describing the risk as no greater than those of everyday life, this was not to imply that they were in any way comparable, say to smoking. BSE was of a much lower order of magnitude. But in the present state of knowledge, it would not be justified to state categorically that there was no risk to humans and it was not appropriate to insist on a zero risk.

The committee recommended additional attention should be directed at abattoir methods in order to minimise cross-contamination of meat with banned offal. The committee also noted with concern the possibility that (a) there was no ruminant feed ban in Eire in spite of the presence of BSE and (b) there are no restrictions on the importation of offal from Eire. ⁹

4.100 However, the terms of the letter to the CMO were not agreed at that meeting. According to Dr Tyrrell, the 'members wished to give a detailed and deliberate response and had some concern that they had been asked to give advice at short notice and outside the ambit of their role. However, they concluded that it was within their role.' ¹⁰

4.101 On the following day, Dr Pickles provided the CMO with 'unconfirmed draft minutes' of the previous day's meeting of SEAC, together with a draft of a letter 'the chairman may be sending to you on the safety of beef'. ¹¹

4.102 Dr Pickles provided the CMO with an updated draft of this letter on 22 May 1990, ¹² but this draft had yet to be agreed by SEAC. ¹³

4.103 On 11 June 1990, Dr Pickles wrote to Dr Tyrrell about the forthcoming SEAC meeting on 13 June 1990. The letter was copied to Mr Lowson. Dr Pickles noted: ¹⁴

You explained to me you wanted the committee to go over and lay out all the fundamental arguments, particularly concerning the safety of beef. I think we have covered much of the ground already and the draft of your letter to the CMO could provide the framework. It does not seem as if there will be time at this meeting for much free-ranging discussion and the best way might be to charge the secretariat (ie, me) with providing an amplified version of the letter to CMO, based on the committee discussion to date, as a paper for circulation before the next meeting. Indeed, I have a draft nearly ready . . . Whilst at the start we said the committee was not going to prepare a report, this paper will be something close to that.

The document described by Dr Pickles in this minute ultimately became the annex to the Committee's letter to the CMO.

4.104 The proposed advice to the CMO on the safety of beef was considered again at the next meeting of SEAC on 13 June 1990. However, it appears that the draft annex being prepared by Dr Pickles was not available for discussion at the meeting. The minutes recorded:

Since it was not yet decided whether CMO would be writing to doctors [on BSE] . . . it was not thought crucial that the chairman finalised and sent CMO his letter on the safety of beef. Indeed, it was preferable for a more detailed paper [in the form of an annex] to come first (a possible was in preparation by Dr Pickles) before the summary letter was agreed. The chairman felt it was helpful for members to clarify their thoughts on this, as on other issues, in writing and this also ensured that they all told the same story. ¹⁵

. . . it was recognised that its [the Committee's] job was to assess scientific data and opinions as objectively as possible, then to set down judgements on these in writing. It was important to communicate the message that science was not absolute and it was for policy-makers to decide what measures to adopt; what action might be appropriate depended not just on what the science indicated but also on what the policy objective was.

It was agreed that it would be necessary to resume discussion on presentation of the arguments on the safety of beef at a later date.

4.105 On 15 June 1990, Dr Pickles sent a minute to Dr McInnes (Private Secretary to the CMO) noting that she and Sir Donald were due to appear before the Agriculture Select Committee the following week. She referred to a document she had drafted for the CMO's appearance, which she felt could also be presented to SEAC. This was the annex to which Dr Pickles had referred in her letter to Dr Tyrrell of 11 June 1990 (see paragraph 4.103, above). Dr Pickles stated:

CMO had asked for detailed information on tissue distribution in scrapie and of intraspecies transfers. At [annex] D is a lengthy document which includes this information in the context of the arguments that are relevant to the safety of beef. This has been prepared by me to help CMO before he is quizzed by the select committee and has yet to be seen by MAFF. The arguments are those that have or should have been discussed by the Tyrrell Committee. It could well form the basis of a mini-report on this subject from the Tyrrell Committee if we can get the paper before them at their next meeting, and such a report would be welcomed by CMO and Ministers. ¹⁶

4.106 The same day, Dr Pickles circulated the document to colleagues within DH for comment. A copy was also sent to Mr Lowson, who forwarded it to Mr Meldrum (and copied it to other MAFF officials, including Mrs Attridge, Mr K Taylor, Mr Lawrence, Animal Health Division, and Mr Maslin, Animal Health Division). Mr Lowson's manuscript note on the covering letter reads:

If I understand Dr Pickles correctly this is designed as a paper for the CMO to issue to doctors. It looks very good to me. It will be considered by the next meeting of the Tyrrell Committee on 2 July at which point I can feed in any points that recipients may have. ¹⁷

4.107 The fourth meeting of SEAC took place on 2 July 1990. ¹⁸ The minutes record that 'subject to some amendments, the draft letter to the CMO was agreed'. The supplementary annex was also 'considered in detail and the secretariat were asked to circulate a revised version for final clearance'. ¹⁹

4.108 Following the fourth meeting of SEAC, Dr Pickles wrote to colleagues in Health Departments in Scotland, Wales and Northern Ireland advising that the CMO was 'still under pressure to write to some doctors (eg, those in public health) about BSE', but that the annex as it stood was 'too lengthy for a routine CMO letter'. ²⁰

4.109 As agreed at SEAC's fourth meeting, a number of changes had been made to the draft letter and to the annex. A revised draft of the letter was circulated by Dr Pickles on 3 July. ²¹

4.110 Mr Murray had taken up post as Head of Section of Environmental Health and Food Safety Division within the DH in June. One of his tasks was to assist on the dissemination of SEAC's advice. ²² In a minute of 4 July to Mr Peter Otley, then acting as his Branch Head, Mr Murray expressed concern as to how the SEAC advice would be received by the public:

Frankly I found the Tyrrell Report worrying. I understand the difficulties of the science of the subject but the Annex will give us considerable presentational problems and do little/nothing to reassure the public about the safety of British beef. Without very much twisting by the media many of the Committee's statements will further fuel the BSE controversy. We must be ready for this through the proposed Press Notice and in our capacity to deal with the subsequent media etc interest. ²³

4.111 On 6 July 1990 Mr Murray wrote to Dr Pickles, expanding on points made at a meeting with her on the previous day:

I understand the need to get the report finalised and put to the Select Committee as soon as possible. However, as we agreed these are aspects of the report which require very careful consideration before we go public on it. In the circumstances I am not sure we can do this adequately within the timescale envisaged in your minute. We need to reach a quick agreement with MAFF colleagues on this point in the light of the CMO's views.

In discussion we agreed that the report required a reconsideration of the terms of recent DH/MAFF assurances on the safety of beef. You mentioned that CMO was already alert to this as a priority matter. Can you confirm MAFF colleagues are aware of this and have advised their Ministers accordingly. I will speak to them if you wish.

I do not want to go too far into the detail of the report at this stage, but it makes comments which will be picked up by the media and contrasted with the prevention of infection measures presently in operation. Here I am thinking of:

in the early stages of infection no (infectious) agent can be detected (para. 3.3);

the infectious agent can be found in tissue not covered by the offal ban (paras 3.4 and 3.5);

it is plausible for small amounts of infection to be present even after cooking (para. 4.6);

the oral route is capable of transmitting BSE (para. 5.1);

there is a suggestion that the young might be more susceptible to infection (para. 7.2);

the agent to which humans are now exposed may behave differently from scrapie (para. 6.5).

I realise that a lot of this is not new. This will not hinder the media in putting a story together. ²⁴

4.112 In his statement to us, Mr Murray emphasised:

I was not concerned about the conclusions of the Tyrrell Report, but how to put them across. ²⁵

4.113 A further draft of the annex was prepared by 6 July 1990. ²⁶ None of the concerns raised by Mr Murray were addressed by the redraft. Indeed, all of the references that caused Mr Murray concern were maintained in the final form of the annex as sent to the CMO.

4.114 Dr Pickles wrote to Dr Tyrrell on 10 July 1990 confirming that she had received his further comments on the drafts 'in yesterday afternoon's post'. She enclosed a further draft and explained that 'the enclosed version takes on board those comments from you on the last draft that were still relevant and those you gave to me on the phone'. ²⁷ Dr Pickles noted:

The other suggestions were from CMO and it is up to you whether you include them or not. He felt a sentence or two on the cat might be helpful since the public and the media thought that was relevant somehow to beef. I have tried to add something in 6.5 on this.

4.115 On the subject of the cat, two additional sentences had been added to paragraph 6.5. This paragraph dealt with the 'apparent' similarities between BSE and scrapie. The additional sentences were as follows:

We do not yet know if the recent description of spongiform encephalopathy in a cat indicates transfer of scrapie or BSE to a new species or whether this is a feline disorder in its own right. In our view, this cat case does not increase the likelihood of BSE transmission to humans. ²⁸

4.116 It should be noted that the first draft of this annex contained the words 'if this is the start of a new cat epidemic it suggests this species could be sensitive to BSE in a way it has not been to scrapie.' This sentence was deleted in the draft of 3 July 1990.

4.117 After dealing with a number of further drafting points, Dr Pickles continued:

[The] CMO when giving evidence to the select committee defined beef as all those parts of the carcass now available for human consumption. Since the committee has yet to discuss mechanically-recovered meat, there could be difficulties in expressly stating the same sentiment here. But maybe you feel there would be no problem in doing so.

Subject to your views, I could circulate again to committee members for information since there has been a fair bit of tidying up since they commented last. We then need to discuss if and when you send it to CMO and what happens thereafter.

4.118 On 10 July 1990, Mr Lowson forwarded both the letter and annex to Mr Gummer, Mr David Maclean, Parliamentary Under Secretary (Commons) at MAFF, and other MAFF colleagues stating: 'The most potentially inflammatory pieces of drafting in earlier versions have now been edited out and I see no particular points that should be raised with DoH about the manner of its publication.' ²⁹ A manuscript note on the accompanying minute states: 'The Minister is content with this draft.'

4.119 We have not found it possible to identify with any precision the 'potentially inflammatory pieces of drafting' ³⁰ referred to by Mr Lowson, nor to identify which drafting amendments were made at the instigation of the Committee and which by the secretariat. The following amendments seem to us to have the effect of removing passages which might give rise to public concern.

4.120 Indeed, the following passages were deleted from the draft of 3 July:

[Tissue distribution of the agent]

3.5 . . . Traces [of the scrapie agent] have also been found in isolated experiments in liver, pancreas and bone marrow [Hadlow et al. (1980) Journal of Infectious Diseases, 146, pp. 657-64] and in lung [Hadlow et al. (1980) Veterinary Pathology, 17, pp. 187-99].

[BSE agent in human food]

4.3 . . . Such agent that does remain may lie in peripheral lymph nodes and possibly in major peripheral nerves, parts discarded in normal meat cutting, but which may still accompany some preparations of meat. Some of the edible offal mentioned in paragraph 3.5 that have on rare occasions demonstrated low titres of infectivity are not included in the offal ban [The Bovine Offal (Prohibition) Regulations 1989] and may also be available.

[The species barrier]

6.4 . . . Of course, it is impossible for any current or past cases of CJD to be causally linked to BSE, since the latter is a very new disease and the CJD incubation period is thought to be several years. ³¹

4.121 In addition, the sentence which we have italicised in the following passage from the section of the paper on risk assessment, was removed from the 3 July draft:

There are some who insist on nothing less than an absolute guarantee of safety. No scientist is in a position to do that at present for British (or Irish) beef. This search for absolute safety is a misconception that adversely influences many aspects of life today. ³²

4.122 As we noted at the outset, the letter and annex were sent to the CMO on 24 July 1990.

Communication of SEAC's advice

4.123 A draft submission to Health Ministers, prepared by Mr Murray on behalf of the CMO, considered the uses to which SEAC's report might be put. It was noted that if presented to the media in a controlled way, the report would be useful in providing reassurances to the public about BSE and the safety of beef. The draft submission also considered that that the report would be of great value to DH and MAFF officials in handling routine correspondence on this issue. It was proposed that a letter from the CMO with a copy of the report be sent to all Directors of Public Health and Chief Environmental Health Officers, and that a copy of this letter would be provided by the MAFF Minister to the Chairman of the Agriculture Select Committee. ³³

4.124 The CMO subsequently circulated the letter and report to all regional Directors of Public Health, explaining that this 'sets out the scientific basis for the statement which I have made on this issue on the 16 May'. ³⁴

4.125 The submission also noted that MAFF Ministers had given an undertaking to the Agriculture Select Committee that all SEAC reports to Ministers would be made public and the same would apply to this report. ³⁵ It would appear, however, that this was not the CMO's intention in this case, as is supported by Mr Lowson's comments subsequently.

4.126 On 10 August 1990, Mr Lowson minuted Mr Maclean stating:

I understand that the Chief Medical Officer is rather sensitive about its being widely publicised. Although a copy has been sent to the Clerk of the Agriculture Committee, Department of Health have not put out any kind of press notice and are circulating it at present only to regional directors of public health.

As I have indicated before, this document is one that could be useful in dealing with the criticism that the Government has not made public the scientific basis of some of the assertions that it has made. It could therefore be used quite widely, for example in the context of the briefing of consumer organisations which the Minister proposed on 12 July. I think therefore that it would be helpful to make it clear that we would intend to use the document perhaps more freely than the CMO proposes. ³⁶

4.127 A manuscript note on the document reads: 'We need to be somewhat careful as the paper does contain some hostages to fortune.' ³⁷ On 16 August 1990, a letter from Mr Maclean was subsequently sent to Mr Kenneth Clarke, Secretary of State for Health, advising:

While under the present circumstances it is not appropriate to draw too much public attention to it, it is nevertheless a paper which should be used to provide background for example to interested organisations and I intend to use it fairly widely in this way. ³⁸

4.128 Similarly, Mr Murray was concerned at the limited state of knowledge held by Environmental Health Officers (EHOs) on BSE matters and minuted Dr Pickles on whether DH should be producing a separate information pack (including the safety of beef paper) for enforcement agencies. ³⁹ In response, Dr Pickles expressed her own concern over the distribution of the safety of beef paper:

We decided some time back to leave MAFF in the lead in providing information on BSE since there was a real chance any subtle differences in material provided by the two departments would be exploited by the media. But a few months back, I felt uneasy continuing that line and originated the 'Safety of Beef' document as our contribution particularly designed for Directors of Public Health and EHOs. As you know, I had intended that this document would be made readily available, with in addition to private circulation from DH/MAFF, publication in Health Trends to make it accessible to the medical community at large . . .

CMO had different views, and at first was not proposing to treat the 'beef' paper as anything other than private advice to him. He then suddenly arranged a limited circulation to Regional Directors of Public Health but without clarifying what he expected them to do with the document. I sense that he would not welcome further advice from me about a wider distribution either of that paper or any document based on it.

Maybe CMO's response to suggestions put up the administrative route might be different. Clearly we would have to discuss any such plans with MAFF since anything I would be happy to see released from DH would have subtle and not so subtle differences in emphasis to material produced by MAFF. ⁴⁰

4.129 Later, Dr Pickles also saw an opportunity for the paper to be used in the Government's response to the Fifth Report of the Agriculture Select Committee on BSE. In a minute dated 12 October 1990 to Mr Lowson, she stated:

Provided we can persuade CMO, it would be an ideal opportunity to add the Tyrrell advice on 'Safety of Beef' as an annex. We want this to be the main message picked up by the media when the Command Paper is published. ⁴¹

4.130 However, the CMO does not appear to have been persuaded. The Government's response to the Select Committee report was published in November 1990 with a single annex relating to the number of suspect cases reported on a weekly basis from 1989 up to 31 August 1990. ⁴²

Discussion of SEAC's paper on the safety of beef

4.131 There are a number of aspects of SEAC's involvement in producing the letter to the CMO on the safety of beef and its accompanying annex which we find unsatisfactory.

4.132 It was not satisfactory for those members of SEAC who could be contacted to be asked to approve the CMO's press release without notice (see paragraph 4.98). We have criticised the terms of that release in that it gave an unqualified assurance that it was safe to eat beef when Sir Donald only felt able to give that assurance on the premise that SBO was being removed from the human food chain. The members of SEAC then found themselves called upon to produce a letter endorsing the CMO's statement. They did not find this an easy exercise and we question the justification for the time they had to devote to it. As Dr Kimberlin commented in oral evidence, the production of the document by SEAC was a catching-up exercise designed, somewhat later in the day, to provide scientific support for what the CMO had said: 'In the ideal world that is not quite the right way round you would do things.' ⁴³

4.133 The letter and its annex were largely drafted by Dr Pickles, and were circulated within DH and MAFF for suggested amendments before going back to the Committee. We have no criticism, in principle, of a secretary to a committee preparing a draft paper for consideration by the committee. What causes us concern in this instance is that, while the documents were intended to represent an expert Committee's appraisal of risk, amendments were being made to the draft by officials whose agenda was not necessarily compatible with the production of a document that fairly reflected the Committee's views. These officials were anxious, first, that the drafts should support the statement made by the CMO, and secondly, that statements which might prove 'inflammatory' (see paragraph 4.118 above) should be edited out.

4.134 It seemed to us that this process carried the risk that SEAC's ultimate advice might be unduly reassuring.

4.135 Our concerns were raised with Dr Tyrrell when he returned to give evidence at Phase 2 of the Inquiry:

MR MATOVU: Were you aware that the draft which you subsequently considered had been circulated around MAFF?

DR TYRRELL: Not in detail, but in principle, yes, because we wanted this to be document which a wide range of people could see and read with understanding and with benefit. I suppose the jargon is we were sending it out to limited consultation. I thought that was helpful, particularly in view of the fact that it might be going to a wider range of people; we did not want it to go public until it had at least had a preliminary canter as to how it was seen by administrators and other people like that.

MR MATOVU: You did not see a possible difficulty in the fact that those Departments who were expecting advice from your committee were in fact feeding in to the advice which was to go to them?

DR TYRRELL: Yes, well -

MR MATOVU: Did you think of that at time?

DR TYRRELL: I think we had already sold the pass; we had already said, 'We are going to be involved in doing things to help a CMO'. We had given up the idea of trying to stand back and do nothing else but evaluate science at a distance and impartially. I think that was something which seemed to be part of what we had got ourselves involved in willy nilly. There is a slight worry that people who have got some sort of departmental personal concern, some axe to grind, might put into it things which were not really there, in our original draft, in our original thinking. But we were going to have it back again at the end to review it, so if somebody said, 'White is black', and we believed that black was white, we would have picked it up and we would have said it.

I thought the possible gain of having other people's angles on it was probably worth it. Do remember that we were all under this worry about what was the outside world, what were the papers, what was television going to make of this thing when it came out? I suppose the people in the Ministries and the politicians would have that as a stronger pressure on them, but we all had it to some extent.

LORD PHILLIPS: Do you think there was a possibility that somebody in one of the Ministries might say, 'That looks a bit too black, let us shade it down to a shade of grey that is likely to be less alarming'?

DR TYRRELL: I think there is a record that even when we got to the end, Robert Lowson said there were inflammatory remarks. Actually, Mr Underhill ⁴⁴ and I went through all the alterations that had been made along the way, as very helpfully laid out in the RFA, and we came to the conclusion that there were none of them that were particularly worrying to us, the possible exception being there was phrase that said, 'No scientist would say there was no risk of eating beef'. That disappeared; perhaps that should not have disappeared, but by and large I think it was an indication of how worried he was about the possible response from outside, rather than that there was anything particularly damaging to his Department which he felt should be excised.

LORD PHILLIPS: Could we just stand back at this point with some hindsight, and ask the question: should a committee like yours have a draft paper it is going to produce on a subject such as this subjected to this kind of process?

DR TYRRELL: That is a tough one.

LORD PHILLIPS: We have to look at some tough ones.

DR TYRRELL: I think, sir, it would depend on the situation. In an ideal world, when it was a reasonable option to get your committee together and let them stand back over a long period of time, or a long enough period of time to do their science and phrase it in a completely acceptable form to all members of the committee, then I think it would be much better, and I would like to avoid even the appearance of the fact that Government Departments could alter it.

I would defend the situation, dropping the hindsight, at the time by saying it was so fraught, almost, that we had to do something, or at least it was seen by those in the Ministry that we had to do something and get it out soon. We had, after all, forced upon them in a way the fact that they had got to wait two or three months from the time that the issue was first raised, was it safe to eat beef? We felt we ought to accelerate the business of consultation to make it a generally useful document. ⁴⁵

4.136 We agree with Dr Tyrrell that there does not appear to have been any editing of the letter and its annex that was 'particularly worrying'. The most significant change was that which related to the commentary on the cat. We suspect that the original version reflected Dr Pickles's conclusions and that members of SEAC did not think it helpful to include discussion of a position that was, as yet, hypothetical.

4.137 Putting hindsight on one side, we accept Dr Tyrrell's 'defence of the situation'. With the benefit of hindsight we are of the view that it was undesirable for SEAC to be asked to endorse advice on the safety of beef when this depended upon matters outside their knowledge, and it was equally undesirable that the advice should have been subject to an editorial process under which officials sought to tone down any passages that might give rise to public concern.

Discussion of the treatment of 'dose'

4.138 We had a further concern in relation to the letter and its annex. This focused particularly on the following comments about dose:

(a) Paragraph 5 of the of the letter stated:

Oral transmission of some spongiform encephalopathies undoubtedly occurs - although very large doses are needed because the oral route is very much less efficient than, say, intracerebral inoculation.

(b) The introductory summary to the annex of SEAC's letter stated that:

Parallels with scrapie and other spongiform encephalopathies suggest the 'dose' of BSE agent if it is indeed present in food as consumed will be so small as to be undetectable by the most sensitive known method for these agents, namely bioassay by intracerebral inoculation into mice. In addition we consider that the oral route of transmission is so inefficient that there is a huge safety margin . . .

5. The Oral Route of Infection

5.1 The oral route is clearly capable of transmitting spongiform encephalopathies in the diseases of BSE and transmissible mink encephalopathy (TME), and it is assumed to be an important natural route of transmission in scrapie and kuru.

5.2 Experimental studies, however, show ingestion to be very inefficient, at least 5 orders of magnitude less efficient than intracerebral injection [21]. In the transmission work done to date with BSE, the incubation period in mice was longer after large oral doses of BSE-infected cattle brain than after much smaller parenteral injections [4,5]. In these as in other animal experiments, large doses, far in excess of what would be experienced in nature, appear to be needed for successful disease transmission.

5.3 It is concluded that the occasional low doses of BSE agent in human food are well below those capable of infecting humans, even if humans were specifically susceptible to the agent. ⁴⁶

4.139 These passages suggested to us, when we read them, that substantial quantities of infective material would have to be eaten by a human before there could be any risk of transmission and that, in practice, this could not occur.

4.140 We raised our concerns with Drs Tyrrell, Will and Kimberlin. Their response was threefold:

(i) All comments about dose had to be read in the context of the risk attaching to consumption of muscle. The letter and its annex made it plain that the premise on which the advice was given was that SBOs were removed from the food chain.

(ii) References to dose related not to the amount of infectious material but to the infectivity of the agent contained in the infectious material. A small amount of material with a high titre would constitute a large dose.

(iii) The letter and its annex were written primarily in order to provide advice to the CMO and to professionals who would have no difficulty in understanding the true concept of dose.

4.141 These arguments did not allay our concerns.

4.142 When giving evidence during Phase 2 of the Inquiry, Dr Tyrrell told us that SEAC appreciated that the annex:

. . . was going to be possibly far more than just a document for the CMO's eyes, that it might go far and wide, and that it might be read by other medics, other scientists, administrators, journalists, all sorts of people might read it. ⁴⁷

4.143 Having heard members of SEAC explain the meaning that they intended 'dose' to bear we can see that it is capable of bearing that meaning, wherever used in the letter and its annex. Nonetheless, it does not seem to us that the reference to the need for a large dose in order to effect oral transmission had any significance unless this carried the implication that such a dose would not be found in a small quantity of infective material.

4.144 We asked Dr Tyrrell what SEAC envisaged when referring in the annex to 'the occasional low doses of BSE agent in human food' in paragraph 5.2 of the annex. ⁴⁸ He replied that in the course of the slaughterhouse operations:

. . . a tiny fragment of the tissue of the cervical spine might have got loose somewhere. We can never say that there could not possibly be any on any meat at all, but our judgement was that this amount was so small that it was not going to reach the concentrations which we guessed would be needed to infect man. ⁴⁹

4.145 This answer reinforced our concern that the reader of the annex might well conclude that contamination as a result of slaughterhouse operations would not involve sufficient infective material to give rise to the risk of transmission.

4.146 In a recent statement to the Inquiry, Professor Barlow, who was not at this time a member of SEAC, had this to say about the comments on dose in SEAC's letter to the CMO:

In most work with BSE, such precision is impossible and most workers have preferred to avoid the word 'dose', though in the pig transmission studies, for example, 'exposure dose was calculated on the basis of replacing the theoretical daily intake of meat and bone meal . . . with an equivalent weight of BSE-infected bovine brain'. ⁵⁰ This seems to suggest that the concentration of active agent, uniformly distributed, in BSE brain and meat and bone meal is similar. It is but a small step from here to equate dose of agent with the amount of potentially infected material administered. Perhaps, that is a useful shorthand way of distinguishing much from little, if one understands the degree of imprecision. This may well be what Keith Meldrum had in mind when he made the point that our mice had consumed more than their body weight of infected brain to become affected - something unlikely to happen with people! Unfortunately David Tyrrell, in his letter to the CMO of 24 July 1990, ⁵¹ used the same shorthand without qualification. In my view his letter also makes too much of the 'inefficiency' of oral compared with parenteral routes of infection. The data supporting that statement were derived from experiments in well-defined systems. It is likely that a suspension of known titre material in saline administered by gavage to a mouse from whom food and water may have been withheld, will be digested differently from infected material eaten on demand over a prolonged period. ⁵²

4.147 In relation to paragraph 5.3 of the annex, Professor Barlow added:

I cannot imagine what the justification was for adding the paragraph . . . unless SEAC had been thoroughly reassured that the SBO ban had been effectively applied in all abattoirs. ⁵³

4.148 It appears from these observations that Professor Barlow shares our view as to the natural meaning of the references to dose in the letter and its annex.

4.149 We have already observed that it is possible to ascribe to SEAC's statements about dose the meaning that they intended those statements to bear. It is also right to note that the advice was primarily intended for professionals who would be expected to understand the concept of dose. In these circumstances, we do not think it would be fair to criticise SEAC for the fact that it is at least possible to draw the wrong inferences from those statements, although it is a pity that the paper did not include a precise definition of dose. It is perhaps fortunate that the CMO did not give the letter and its annex the wide circulation that Dr Pickles had hoped that it would receive. It is not clear how widely the documents were circulated within MAFF. The evidence shows that in 1990, and indeed for some years thereafter, there was a perception on the part of many within Government that a substantial quantity of infective material would be required orally to transmit BSE to a cow and that the same would be true of transmission from cow to human, if indeed such transmission was possible. The letter of 24 July 1990 and its annex may well have played a part in fostering these views.