Volume 4: The Southwood Working Party, 1988-89
10. Discussion
The risk from the tissues of subclinically infected animals
The conclusions of the Southwood Working Party
The role of the Working Party

10.53 The Working Party's vigorous reaction against the entry into the human food chain of any part of an animal showing clinical symptoms of BSE contrasts with their attitude to animals infected with BSE that were slaughtered before clinical symptoms had developed. This was a matter which they considered at their second meeting on 10 November 1988. Before that meeting Dr Pickles had circulated a first attempt at drafting some of the sections of the Report. This included the following suggestions of possible precautions in addition to the exclusion from the human food chain of affected cattle:

Ox-brain would carry more BSE agent than other edible parts. It is eaten rarely in this country and it could be questioned whether restricting ox-brain for human use to imports from overseas would create any opposition, and be seen as a sensible further move. Brain and lymphoid tissue could be omitted from meat pies without any important consequences for the industry and certainly without any culinary loss. Temperatures in meat pie manufacture are not always high enough to destroy agents such as scrapie. ¹

10.54 At their second meeting the Working Party rejected the idea of a ban on United Kingdom ox-brain for human consumption, but proposed to suggest that there was a case for labelling to indicate whether processed food contained brain in order to enable an informed customer to make his or her own choice. It was observed that, if accepted, this course was likely to cause the meat pie industry to find alternatives to brain rather than to include it with labelling. ² Subsequently, after Mr Cockbill had advised that certain technical hurdles would have to be surmounted under European Community Regulations before brains could be labelled, the suggestion of labelling was abandoned. In the event the only recommendation made by the Report in relation to the oral ingestion of tissues from subclinically infected animals was the baby food recommendation. The Working Party explained to us in some detail why they decided that no precautions, other than the baby food recommendation, were justified in this area:

Based on the scientific evidence known to us as at 20 June 1988 we viewed the risk posed to human health by tissues and fluids from asymptomatic infected cattle as sufficiently low for the highlighting of a potential risk to human health to be unnecessary. Later in our deliberations we identified good reasons to reach a different conclusion for the very young.

. . . the evidence before us was that the titre of infective material in certain tissues such as brain and spinal cord of asymptomatic animals only reached high levels shortly before clinical signs developed. On the evidence available to us the potential risks posed to the adult human population by asymptomatic cattle through the oral route of transmission were minimal. ³

10.55 They summarised their reasons for not recommending the banning of ox-brain as follows:

(i) We had already requested removal of symptomatic cattle from the human food chain.

(ii) Scrapie was the model on which we had to rely for taking action.

(iii) The titre of tissues, including brain, in subclinical scrapie is generally low. (Hadlow et al.)

(iv) Comparatively small numbers of cattle were being notified as affected (1,365 at the end of October 1988 [0.01% of the national herd]).

(v) Epidemiological information supplied to the Working Party suggested that the outbreak was plateauing.

(vi) The mean incubation period we were informed was 4 years, ie, after calves (up to 6 months) and prime cattle (12-30 months) are killed and before the majority of dairy cows are slaughtered (6-7 years).

(vii) Brains of cattle are generally destroyed during the process of killing.

(viii) Consumption of brains was low and if used they were required to be cooked.

(ix) Banning consumption of brains would require EC approval and could be difficult.

(x) The greatest estimated danger was to certain occupations (vets, slaughtermen, etc) or by pharmaceutical preparations given by injection.

(xi) The majority of affected cows were dairy stock. ⁴

We observe that a number of these reasons were equally applicable to other tissues.

The conclusions of the Southwood Working Party

10.56 The Working Party gave no explanation in their Report for their conclusion that the risk from eating brain and other possibly infective tissues of subclinical cases of BSE did not call for any general precautionary measures. This was unfortunate, for it made it impossible to carry out a reasoned review of their conclusion. Had they set out in their Report the factors that they enumerated to us, the validity of each could have been considered. The subsequent escalation of the epidemic, which they had not anticipated, would of itself have demonstrated that their Report could no longer be treated as valid scientific guidance on precautionary measures. More fundamentally, we do not consider that the factors enumerated by the Working Party justify the conclusion that they based upon them.

10.57 On 13 November 1989 the first Specified Bovine Offal (SBO) ban was introduced, taking out of the human food chain those bovine tissues that might, in subclinical cases of BSE, carry infectivity. ⁵ The question arises why, if the Working Party applied the ALARP principle, they did not recommend general measures of this type to deal with the risk posed by subclinical BSE cases.

What was reasonably practicable?

10.58 With hindsight it is clear that the human SBO ban was a desirable and proportionate measure to address the risk posed by subclinical animals. In a letter to Dr Reimer Böge of the European Parliament dated 20 December 1996, Sir Richard said:

Although there is as yet no evidence that the titre of the agent in the specified offal is sufficient to infect humans orally I believe that their removal is a precaution that should have been taken in 1988, rather than the next year. But I must stress that this is because the precautionary aspect must now be weighed more heavily as since last April we believe that the agent may be transferred, presumably if present at a sufficiently high titre, to humans. ⁶

10.59 Members of the Tyrrell Committee told us that when they began their duties in March 1989, they had concerns about subclinical BSE cases. Thus Dr David Tyrrell, while paying tribute to the Report, added:

I would have given more emphasis to the probable large numbers of infected cattle which would be by now around, and what we were going to do about them ⁷ ... Having read Richard Kimberlin's papers, I was aware that there could be large amounts of infectivity in tissues of animals which were healthy, and if these were not removed in some way or another, then they would also expose human beings to risk. ⁸

10.60 Dr Kimberlin commented:

I think what Southwood did in the short space of time that he had available to him was admirable, and he did the obvious easy things, and that was fine, but it became very clear to some of us anyway that that would not be enough. ⁹

10.61 Dr Will said:

. . . we were aware that the specified bovine offals ban was going to be introduced, I think, around that time . . . June . . . That to me was an absolutely critical measure to protect public health, because it would remove CNS [central nervous system] tissues from infected cattle which could not be identified clinically, in addition to the removal of affected cattle that were identified . . . ¹⁰

10.62 Insofar as these statements purported to reflect views at the time that the Southwood Report was published, we treat them with caution. Witnesses are not immune from the temptation to be wise after the event. There were, however, some who expressed concern about the risk posed by tissues of subclinical animals at the time.

10.63 By the time of the Working Party's second meeting, Dr Timothy Holt and Ms Julie Phillips had published a perceptive article in the British Medical Journal drawing attention to the potential risks of products derived from the brains of asymptomatic victims of BSE. ¹¹

10.64 On 1 November 1988 Dr Fraser, Head of Experimental Pathology at the Neuropathogenesis Unit (NPU), wrote to Dr Holt inviting him to discuss his concerns about preclinical animals with the NPU:

Our work on scrapie highlights our lack of knowledge on BSE such as the levels of infection in healthy cattle incubating the disease. The incorporation of lymphoreticular tissue such as spleen into meat products is just one example of a policy which may be difficult to sustain. ¹²

10.65 On 2 March 1989 the Guardian published a letter from Dr Helen Grant, an experienced neuropathologist at the Middlesex and Charing Cross hospitals, expressing concern about animals incubating BSE. Shortly afterwards she wrote to Sir Richard:

The report of your working party is quite first class both as to the collecting of factual material and as to recommendations. The only criticism I would be inclined to level is that the ominous problem of the incubation period is not given enough emphasis. Since it is impossible by testing them to reveal which animals are infected (as opposed to 'affected') the long incubation period is potentially very sinister because these animals continue to reach our food. ¹³

10.66 Sir Richard replied on 13 March:

As you can imagine, in this Report it was extremely difficult to steer the proper course between causing excessive alarm and undue complacency. The evidence to date seems to indicate that the BSE agent is very similar to scrapie, and of course we have lived with scrapie for two hundred years, and most of us have at some time or other eaten sheep offal - though the incidence of CJD remains low. It was this line of argument that finally convinced us not to press the point that you have made in your letter any more strongly. ¹⁴

10.67 We believe that had the Southwood Working Party correctly applied the ALARP principle, and had they been informed of the measures that were available to reduce risk and their practical implications, they would have recommended the precautionary measures that were subsequently adopted under the SBO ban. This conclusion is based upon knowledge available at the time.

10.68 When speaking of their reaction to affected animals entering the food chain, Sir Richard quoted one of his colleagus as saying: 'Good gracious, a lot of the CNS system must still be left in the spinal column, and that must go in the food chain getting into mechanically recovered meat and so on.' ¹⁵ The same was true of the subclinical animal.

10.69 Later he added, in relation to ox-brain:

We continued to be concerned because, I think I can remember Sir Anthony saying, what about the animals that are not showing symptoms but will obviously have some of the agent in their brain and nervous core; and we all thought: 'What can we do about this? But it is the whole British cattle herd. How were we going to deal with that? Was there some way we could find the part of that which was at most danger and somehow exclude it from the human food chain?' It might well be it may still be true that the titre would not be sufficient to cause a disease certainly ingested, that we do not know even today. We did explore it. Those are the minutes written in the way you saw. We accepted the minutes. We obviously continued to worry about this, particularly in relation to baby food, and you will have before you the paper from Mr Cockbill dated on 12 December, which I did not have available when I prepared my memorandum initially, but then I was able to incorporate it.

In some paragraphs, I refer to the problems of the EC and so on, all of which were produced as reasons why it would be difficult to label food as containing ox-brains. In general, I think the message we got was [that it was] going to be a very difficult procedure to follow. We continued to worry away at that right the way through to the end. ¹⁶

10.70 It was, or should have been, plain that there were substantial numbers of asymptomatic infected animals being slaughtered for food. The Working Party, rightly, were not convinced that the outbreak was plateauing. The CNS tissues of sheep clinically affected with scrapie had been demonstrated to have higher titres of infectivity than those of asymptomatic infected sheep. In contrast, the level of infectivity in the lymphoreticular system reached its maximum about a year before clinical symptoms appeared. There was no sound basis for concluding that either type of tissue would be incapable of infecting, even if it were safe to conclude that experience in relation to sheep could be applied to cattle. The Working Party could not, however, be confident of that. As Sir Richard said to us:

What we, of course, were also very concerned to know is: how did the titre of the agent build up in those particular tissues during the progression of the infection over five years in a cow, because that is absolutely fundamental to the extent of the risk that existed after 1988 . . . it has been six or seven years before we really got any information of that sort. ¹⁷

10.71 The Working Party concluded, and rightly concluded, that it was not safe to proceed on the basis that it was certain that BSE would not transmit orally to humans. They concluded that action was called for to meet the risk that BSE would not behave like scrapie. They were driven to that conclusion by uncertainty.

10.72 Just as there was uncertainty as to whether BSE would behave like scrapie, there was uncertainty about the nature and transmission of TSEs. In August 1987 Dr David Taylor of the NPU wrote to advise Mr John Sloggem of DH's Medicines Division, who was concerned about the risk of a proposed oral medicine that incorporated bovine brain extract. Having given examples of natural oral transmission of TSEs (kuru and TME) and experimental oral transmission (scrapie into mice; and kuru, CJD and scrapie into squirrel monkeys), Dr Taylor concluded:

Oral transmission has not been studied experimentally to anything like the extent that the intraneural route has, and so we know little of the efficiency of the route for infection or how agent gets from the gut to the brain. One would think instinctively of it being a less efficient route, but it is impossible to quantify this on the basis of existing data. ¹⁸

10.73 In our judgement this uncertainty should have precluded the nice distinctions the Working Party made between the risk to babies and the risk to other humans.

10.74 Mr Meldrum commended the Southwood Report. He said, however, that when he came to reflect on it he detected an illogicality. That perceived illogicality was remedied by Mr John MacGregor's decision to introduce the SBO ban, which Mr Meldrum described as 'inspirational'. ¹⁹

10.75 We agree with Mr Meldrum that the Southwood Report had an illogicality. If slaughter and destruction of animals showing symptoms of BSE was, as we believe it was, a reasonable response to the possibility, albeit seen as remote, that BSE might be transmissible to humans, it was illogical not to remove the potentially infective offal from cattle not showing symptoms.

10.76 In this context we should refer again to the conclusions of the International Round Table (see paragraph 10.18). It is significant that, while endorsing the Southwood Report, this body commented that: 'Until additional information is obtained, tissues, with the exception of nervous tissue ((brain, spinal cord) and perhaps some of the major lymphoreticular organs from unaffected animals of the same herd, are not believed to be a source of any further danger than that already incurred by allowing scrapie-infected sheep or goat tissues to enter the human food chain.' (Emphasis added.) ²⁰

10.77 In written submissions addressing the question of whether they should have recommended precautionary measures that went further than the baby food recommendation, the Working Party said:

. . . it was reasonably practicable for the limited number of manufacturers of baby food to control the ingredients of their products. We judged it was neither necessary nor reasonably practicable to go further. Any recommendation for older individuals would have had to read along the lines 'butchers and others should not incorporate offals in their products or sell the same'. As so many outlets would be involved this would have required a regulation and we were advised that this would involve many difficulties (ie, was not reasonably practicable) (see Mr Cockbill's letters to us - RFA 1 paragraph [391], 12 December 1988. ²¹ It would almost certainly have created a crisis in the beef industry such as that which we have subsequently observed. Given that we and others were agreed that the scrapie analogy was the most reliable guide to the risk to humans and that we understood that the 'dose' (if any) to adults would be less, then such a further recommendation was not necessary and, we believe, would have been regarded at the time as highly irresponsible.

10.78 We would comment on this submission as follows:

1. the SBO ban provided a practicable means of removing high risk tissues from general consumption;
2. the SBO ban did not create a crisis in the beef industry. On the contrary, it was considered desirable to introduce the measure as a reassurance to consumers of beef;
3. there would have been nothing irresponsible about recommending an SBO ban; but
4. the reality was that the possibility of this precautionary measure was not drawn to the attention of the Working Party.

10.79 The Working Party told us that, when considering measures to deal with BSE, they considered the slaughter of the entire herd and concluded that that would be disproportionate. ²² We do not believe that they considered the possibility of an SBO ban of the kind that the Government introduced later, although they did consider a ban on the consumption of brain. Sir Richard said of the SBO ban that 'the Ministry had found a way of dealing with the whole cattle herd other than slaughtering it', and that he in no way resisted that ban being introduced. ²³

The role of the Working Party

10.80 We do not believe that the Working Party was an appropriate body to make detailed recommendations about an SBO ban. They did not have the expertise or the data needed to take the policy decisions. Practical decisions could not properly be taken without reliable knowledge of the routes by which and the extent to which the various parts of the cow entered the human food chain. They could not be taken without detailed scientific advice, beyond the expertise of the Working Party, as to the likely infectivity of the various tissues. They could not be taken without knowledge of the practicability of removing those tissues from the human food chain and the financial implications of so doing. On 12 April 1989, in a note to Dr Watson, Mr Raymond Bradley (Head of the CVL's PathologyDepartment) advised:

It is quite clear that in an infected animal in the late preclinical phase . . . lympho-reticular tissues and certain other tissues, including some endocrines . . . plus CNS, are highly likely to be infected to a high titre of significance to humans if the agent is transmissible to them . . . It is a big step to take to try to eliminate certain items from the food chain. However, it would be relatively simple to reduce risks considerably by sending for rendering or incinerating specified easily identified organs and ensuring the necessary training and adjusted slaughter and butchering procedures to reduce cross-contamination. Spleen, uterine . . . all endocrines, heads (unopened but after removal of muscular tissue) and spinal cord from sheep over 1 year and cattle over 2½ years could be designated unsaleable for human consumption. ²⁴

10.81 Considerations such as these were not discussed by the Working Party, and we do not suggest that they should have been. What we believe that the Working Party could and should have done was to advise that cattle infected with BSE, that were entering the human food chain, had tissues which were potentially infective and that consideration should be given to identifying such steps as were reasonably practicable to prevent their being eaten, not just by babies but by everyone.

10.82 The failure of the Southwood Working Party to make such a recommendation in relation to the risk of transmission posed by asymptomatic cattle was a shortcoming which should not overshadow the credit due to the Working Party for a series of prompt and valuable recommendations. Happily, the baby food recommendation focused attention on the problem of the subclinically infected animal, and led to precautionary measures being put in place that went beyond those recommended by the Working Party.