Volume 4: The Southwood Working Party, 1988-89
9. The drafting of the Report

9.1 In the letter presenting the Report to Ministers Sir Richard wrote:

I, and other members of the Working Party, would like to thank our expert adviser, witness, correspondents and secretariat for their contributions and assistance. The Report, however, remains our own. ¹

9.2 The General Conclusions, which formed Chapter 9 of the Report, were drafted by Sir Richard in circumstances which we shall describe. The majority of therest of the Report was produced as a joint effort, the drafting being done by Mr Wilesmith, Mr Lawrence and Dr Pickles with input from and subject to the editing of the Working Party. ² Chapter 2, 'A History of Bovine Spongiform Encephalopathy', was drafted by Mr Wilesmith and Mr Lawrence and provided background information to the Working Party on matters which fell outside their own knowledge and experience. Chapter 3, 'Transmissible Spongiform Encephalopathies', was drafted by Mr Lawrence, Mr Wilesmith and Dr Pickles on the basis of an analysis of a substantial number of published papers, the references for which are provided. This chapter was one which the Working Party were in a position to alter or approve on the basis of their own studies of papers referred to. Chapter 4, 'The Cause of Bovine Spongiform Encephalopathy: The Epidemiological Evidence', was drafted by Mr Wilesmith. It set out his own conclusions based largely upon his own epidemiological studies. The chapter explained the basis upon which meat and bone meal was identified as the cause of infection. It included the following passages:

4.2.1. The epidemiological picture, as shown by the distribution of cases by month and year of onset . . . is typical of an extended common source epidemic. Movement of cattle between known affected herds does not account for the occurrence of cases and the initial cases in different herds developed clinical signs within a relatively short period of each other. All affected animals therefore appear to be index cases . . .

4.2.4. The occurrence of TME in ranch-reared mink, first recorded 40 years ago, seems to be a precedent for the food-borne transmission of the agent. The source of the infection in ranched mink in the USA was attributed to the feeding of scrapie-infected sheep or goat tissues . . .

4.2.8. There is no clear or single explanation why it appears that in 1981/82 cattle apparently first became exposed to an agent sufficient to result in clinical disease. On the other hand a number of factors have been identified which, combined, could be important in the occurrence of this epidemiological phenomenon. These include a significant increase in the sheep population in Great Britain which commenced in 1980 and has continued since; a possible increase in the prevalence of scrapie-infected flocks; the greater inclusion of sheep heads in material for rendering; the greater inclusion of casualty and condemned sheep in material for rendering as a result of the reduction in the number of knackers' yards; the introduction of continuous rendering processes during the 1970s and 1980s, which may have resulted in the rendering of animal material at a lower temperature and/or for less time than previously, and the decline in the practice of using hydro-carbon solvents for fat extraction since the mid-1970s. These factors provide a possible explanation for a change in exposure of cattle to ovine-derived protein and thus the scrapie agent.

4.2.9. A further hypothesis to explain the occurrence of BSE is the emergence or selection of a strain or strains of the scrapie agent pathogenic for cattle. Mutations of the scrapie agent, which can occur after a single passage in mice, have been well documented. This phenomenon cannot be dismissed for BSE, but given the form of the epidemic and the geographically widespread occurrence of BSE, such a hypothesis would require the emergence of a mutant scrapie strain simultaneously in a large number of sheep flocks, or cattle, throughout the country. Also, if it resulted from a localised chance transmission of the scrapie strain from sheep to cattle giving rise to a mutant, a different pattern of disease would have been expected: its range would have increased with time.

9.3 The Working Party did not see it as their role to conduct a critical review of Mr Wilesmith's conclusions. To have done so they would have needed to consider the primary data that led to those conclusions. Mr Wilesmith explained to them that some of those data were confidential. ³

9.4 Chapter 5, 'The Transmission of Bovine Spongiform Encephalopathy', was drafted in part by Mr Lawrence and Mr Wilesmith and in part by Dr Pickles. In dealing with transmission in cattle the chapter referred to the experience of maternal transmission in sheep and then continued:

5.1.2. . . . Although the disease in goats behaves in a similar way to that in sheep, some species, such as rodents and mink which are susceptible to scrapie, act as dead-end hosts with no direct animal to animal transmission. At the present stage of knowledge it is impossible to predict whether cattle to cattle transmission of BSE will occur.

9.5 The chapter went on to refer to the fact that BSE had been transmitted experimentally by intracerebral inoculation into mice and to state that the possibility existed of transmission to other animals, including domestic pets and mink. The second part of the chapter, for which Dr Pickles was primarily responsible, dealt with possible transmission to man. The latter part of Chapter 5 gave rise to considerable discussion and the Working Party was involved in the formulation of its conclusions. These included the following:

5.3.1. Kuru and Creutzfeldt-Jakob Disease demonstrate that humans are susceptible to spongiform encephalopathies. The potential routes of transmission of BSE from cattle to humans have been examined closely. With the very long incubation period of spongiform encephalopathies in humans, it may be a decade or more before complete reassurance can be given.

5.3.2. Information from several spongiform encephalopathies suggests that parenteral inoculation is much more efficient in transmitting disease than oral or topical exposure and that neural, and to a lesser extent, lymphoid tissue carry the infection whilst the risk is far less with other tissues. The theoretical routes of transmission from cattle to humans can be presented in 'risk' order to help clarify whether action is appropriate or research worthwhile.

5.3.3. The greatest risk, in theory, would be from parenteral injection of material derived from bovine brain or lymphoid tissue. Medicinal products for injection or surgical implantation which are prepared from bovine tissues, or which utilise bovine serum albumin or similar agents in their manufacture, might also be capable of transmitting infectious agents. All medicinal products are licensed under the Medicines Act by the Licensing Authority following guidance, for example from the Committee on Safety of Medicines (CSM), the Committee on Dental and Surgical Materials (CDSM) and their subcommittees. The Licensing Authority has been alerted to potential concern about BSE in medicinal products and will ensure that scrutiny of source materials and manufacturing processes now takes account of BSE agent.

5.3.4. Direct inoculation of bovine tissue could also occur accidentally in certain occupations, such as slaughtermen, veterinarians and laboratory workers. Guidance on safe working practices in general are drawn up by the Health and Safety Executive who have been alerted to the potential concern about BSE and in particular to the possible infectivity of placentae. No specific additional guidance on BSE is thought appropriate at this time. However adherence to recommended procedures in handling animals and animal products is clearly very important.

5.3.5. In these, as in other circumstances, the risk of transmission of BSE to humans appears remote. Nevertheless, because the possibility that BSE could be transmitted orally cannot be entirely ruled out, known affected cattle should not enter the human food chain and action now undertaken ensures this. What evidence there is does not suggest that milk can transmit any of the spongiform encephalopathies. Nevertheless, to be consistent with the earlier recommendation that cattle known to be infected with BSE should not be offered for human consumption, we have recommended that milk from cows suspected as having BSE should be destroyed. Action has also been taken here. Finally if the BSE agent were to be present in an animal it is most likely to be in the spleen and lymphatic tissues in the early stages of infection, and as the disease progresses in the brain and neural tissue. It has been suggested, although clinically affected cattle are being slaughtered and destroyed, that consideration should be given to products containing brain and spleen being so labelled, to enable the consumer to make an informed choice. The Working Party believes that risks as at present perceived would not justify this measure. We note that current regulations that require contents of processed food to be listed permit the generic terms 'meat' and 'offal'. We consider that manufacturers of baby foods should avoid the use of ruminant offal and thymus; the latter can currently be described on food labels as meat.

9.6 This advice on baby food was the only precautionary guidance given by the Working Party in relation to the risk of transmission from eating infective tissues from asymptomatic animals. By way of convenient shorthand we shall refer to it as 'the baby food recommendation'.

9.7 Chapter 6, 'The Future Course of the Disease', was drafted by Mr Wilesmith after considerable discussion with the Working Party. The possibility that the insertion of infected cattle into the cattle food chain until 18 July 1988 could have increased the exposure was recognised, but the extent of it was stated to be impossible to quantify and possibly minimal and undetectable 'resulting in essentially a constant exposure'. The chapter continued:

6.1. . . . If this is the case, and given the incubation period distribution, then a constant number of cases, of the order of 350-400 per month, can be expected; this is an incidence of 1 case per 1,000 adult cows per year. If the age structure of the national adult herd remains constant, as the usual life span of a milk cow in Great Britain is at present 5 to 6 years this rate of presentation of the disease will continue until 1993, a cumulative total of about 17,000-20,000 cases from cows currently alive and subclinically infected. Thereafter, if cattle to cattle transmission does not occur then a reduction in incidence would follow with a very low incidence in 1996 and the subsequent disappearance of the disease.

9.8 Sir Richard Southwood had reservations as to whether cases of BSE had plateaued - reservations which were shared by Dr Pickles. The Working Party did not, however, feel that they were in a position to dissent from Mr Wilesmith's conclusions. ⁴

9.9 The chapter went on to consider the possibility of maternal transmission and concluded:

6.2. . . . Though maternal transmission would increase the number of cases on its own it would probably be insufficient to sustain BSE in the national cattle population because it is likely that the number of offspring per case which will reach a susceptible age and produce their own offspring will be less than one.

9.10 The chapter then reverted to the possibility of the transfer of BSE to other species:

6.3. . . . It cannot automatically be assumed that animals and man will react to BSE agent exposure as they have done to scrapie, which in the human case has not led to any clear association with disease . . . BSE agent may for example be an adapted or particularly virulent form of scrapie agent although the results of the epidemiological study indicate otherwise.

9.11 The chapter ended with a section which represented input from Sir Richard:

6.4. Zoonoses

Zoonoses are diseases of animals which present a risk to human health through a pathway of infection. Many diseases have arisen in this way for a large number of pathogens can infect man as well as animals. Brucellosis and bovine tuberculosis (TB) are examples that have been of great concern in the recent past in Great Britain. At present the common zoonoses in Britain are salmonella, listeria and campylobacter food-poisoning. Changes in the habits of humans lead to the opening up of new pathways of infection and predispose to the emergence of new zoonoses. The increased efficiency of modern agriculture has in part been achieved by its intensification and by short-circuiting natural pathways, as, for example in recycling animal waste, i.e. feeding animal waste to chickens, cattle and pigs. Such procedures have many advantages: they reduce the loss of nutrients and they increase the growth or output of the animals, whilst at the same time disposing of waste materials that are themselves potential health hazards and pollutants. However ruminants are not by nature scavengers, thus unlike hyaenas, foxes or vultures they will not have evolved defences against the transfer of pathogens from animal wastes; as the Royal Commission on Environmental Pollution warned in its 7th Report, 'the major problem encountered in this recycling process is the risk of transmitting disease-bearing pathogens to stock and thence to humans' . . . Some recent zoonoses, like bovine TB and brucellosis, have been controlled but strict measures are often needed to eliminate the risk to humans from these animal disorders.

9.12 Chapter 7, 'Actions Already Taken to Reduce Spread of Disease', described the ruminant feed ban, the slaughter and compensation policy, and the destruction of milk from BSE suspects. The Report considered whether there was evidence to suggest evasion of the slaughter requirement and concluded that there was not. ⁵

9.13 Chapter 8 set out the 'Further Recommendations' of the Working Party. The first of these re-emphasised the desirability of ensuring that the 300 offspring of affected animals and the 300 controls that were being monitored should not be destroyed before becoming old enough to display the disease, should they be infected. ⁶ The next recommendation dealt with medicinal products:

8.2. Consideration has been given to the potential for the transmission of BSE between cattle and other species, including man, through the use of medicinal products . . . Although the risks appear remote the Working Party recommended that the attention of the Licensing Authority, the Committee on Safety of Medicines (CSM), the Committee on Dental and Surgical Materials and the Veterinary Products Committee (VPC) be drawn to the emergence of BSE so that they can take appropriate action. In this connection the Chairman of the Working Party has corresponded with the Chairman of the CSM and with the VPC.

9.14 The next recommendation dealt with health and safety:

8.3. Paragraph 5.3.4 draws attention to a number of occupational groups, such as veterinarians, slaughtermen, herdsmen and laboratory workers, who could conceivably be exposed to the BSE agent. It is recommended that the potential problems caused by BSE are brought to the attention of the Health and Safety Executive who can consider whether further guidance should be given to such groups.

9.15 Next there was a recommendation for surveillance:

8.4. Monitoring of cases of Creutzfeldt-Jakob Disease should take place, both through the neurological network and by OPCS [Office of Population Censuses and Surveys], since any human cases of BSE would present as CJD . . .

9.16 Finally, the recommendations dealt with research. Reference was made at paragraphs 8.5.1-2 to the establishment of what became known as the Tyrrell Committee (the Consultative Committee on Research), and the following eight areas of research were identified as particularly deserving consideration by that committee:

(i) Epidemiological Studies - in particular to examine further the role of meat and bone meal as the source of BSE and to determine whether or not maternal (vertical) and horizontal transmission can take place.

(ii) Transmission studies in a variety of possible host species. Transmission to mice has already been demonstrated at the MRC/AFRC Neuropathogenesis Unit. We understand that other studies are underway or planned using cattle, marmosets, hamsters, mink and goats. Parallel cattle studies are also planned using the scrapie agent. Further projects are planned, using material from affected cattle, to determine whether or not transmission is possible via semen and embryos. Follow-up studies should be designed to determine the physical and chemical processes to which the agent is susceptible and thus the conditions required to make material (such as rendered infected carcasses) 'safe'.

(iii) Transmission experiments using muscle and milk, in the latter case to repeat earlier experiments which showed that milk was not a vehicle for scrapie transmission to any species.

(iv) Possibility of formal monitoring of the health of pigs and domestic pets, particularly since pigs are used in the manufacture of some pharmaceuticals. Transmission experiments may be relevant for some of these species. We assume that there is no intention to exclude these animals from the [Tyrrell] Committee's terms of reference, and believe that the departments concerned will recognise the dangers of excluding these potential infective pathways.

(v) Studies to determine whether the BSE agent is identical in its molecular structure to the natural agent of scrapie or modified in some way. Determine whether there are single or multiple strains and the relationship to agents responsible for transmissible encephalopathies in other species.

(vi) The determination of the nature of the infectious agent: clearly this would be a tremendous breakthrough as would a means of positively identifying the infection in subclinical form. However, the difficulties of achieving this are acknowledged and the scrapie experience exemplifies the difficulties of making progress in this direction.

(vii) Genetic studies to determine whether there are any genetic factors involved in the disease expression in cattle.

(viii) The surveillance of humans at particular 'risk' and formal monitoring of CJD cases, particularly in occupational groups exposed to bovine tissues.

9.17 These recommendations ended with the following observations:

8.5.3. The Working Party regards research as essential, for if there is any vertical or horizontal transmission the results will have a critical bearing on whether or not there is sufficient understanding of the disease to be able to control and eventually eliminate it. It will also have vital implications in terms of the ability or otherwise to maintain our important export trade in cattle, semen and embryos. And above all it may lead to complete reassurance about the lack of risk to human health or point the way to eliminating practices that could open up new pathways for infection.

9.18 Chapter 9 of the Report set out four General Conclusions. Sir Richard was the author of these. The first three conclusions were as follows:

9.1. Bovine spongiform encephalopathy belongs to a group of diseases that are particularly intractable: the precise nature of the causative sub-viral agent is uncertain, their incubation periods are long, diagnosis is difficult except in the terminal stages and the mechanisms of transmission are variable and often obscure. One such disease, scrapie, has been widespread in sheep flocks in Britain and in other countries for at least two centuries, whilst CJD, a human encephalopathy with a worldwide distribution, has remained rare.

9.2. From the present evidence, it is likely that cattle will prove to be a 'dead-end host' for the disease agent and most unlikely that BSE will have any implications for human health. Nevertheless, if our assessments of these likelihoods are incorrect, the implications would be extremely serious. Thus, we greatly welcome the speed with which the Ministry of Agriculture, Fisheries and Food has brought forward regulations based on the veterinary evidence and on our recommendations and are encouraged by what we have learned of the positive response from the animal foods and farming industries to ensure the effectiveness of the regulations.

9.3. Assuming there is no vertical or horizontal transmission, the strict adherence to the regulations preventing the incorporation of infective material in calf and cattle feed should (after about 4 years) lead to a fall in the number of new cases and, on present evidence, after about 9 years the disease is likely to be extinct in Great Britain. In the meantime, farmers will have to exercise continual vigilance to ensure that animals exhibiting early symptoms are identified and prevented from entering the human food chain.

9.19 The phrase 'dead-end host' has given rise to some confusion, for not all use it in the same way. Some use it to describe the species in which an animal infected by a TSE will not naturally pass on the infection to another member of the species, let alone to a different species. Sir Richard was asked about this phrase during his oral evidence; he replied:

That was a term that was applied to mink when, in that particular case, it passes into the female, to the adult mink, but did not appear to pass to the kits. I will agree with you, it is a slightly ambiguous term. It could well mean it remained in cattle but did not pass to any other species. ⁷

9.20 Subsequently, Sir Richard has explained to us that he used the phrase in the General Conclusions to describe a species within which natural transmission of the TSE will not take place to an extent sufficient to make the disease endemic. It is necessary to give the phrase this meaning if the conclusion is to reflect the balance of the Report, for it is quite clear that the Working Party had not discounted the real possibility of maternal transmission.

9.21 The final General Conclusion, which was drafted by Sir Richard, read originally as follows:

This problem has arisen as a result of the practice of feeding animal materials to herbivores, which are thus exposed to infection/infective risks against which they have not evolved any defences. Such practices are often a feature of modern intensive agriculture, but inevitably (as with BSE and bacterial pathogens in poultry) they open up new pathways for infection to the herbivores and potentially from them to man, via food and/or medicinal products. We note these animal meal supplements do increase the rate of growth of the animals, whilst also providing a superficially efficient way of disposing of animal waste. But we believe that the inevitable risks are such that it would be prudent to change agricultural practice so as to eliminate these novel pathways for pathogens. We urge the Minister to address this general problem as part of the adjustment of the framework of the agricultural policy of the EEC in the coming years. ⁸

9.22 In reporting to the CMO, Dr Pickles said that this conclusion had been 'sprung on his colleagues and the secretariat at the meeting'. She added:

Appreciating that this was a sensitive conclusion which is best kept confidential at the moment, and because all the recommendations for immediate action have already been acted upon, we decided to delay completion and presentation of the report until mid-February. However, alarm bells will be ringing already in MAFF and they may attempt to steer Sir Richard away from a general statement of this sort. These remarks are within the terms of reference of the working party.

Perhaps it's just as well that we have now arranged for DH to take over from MAFF the final stages in preparing the report. The official excuse was that I had better secretarial support than my colleague in MAFF. ⁹

9.23 Sir Richard had appreciated that this recommendation might not be welcome to MAFF and had deliberately kept it up his sleeve until this third meeting and decided that, from then on, the perfecting of the draft of the Report would be done by the Working Party themselves, with assistance from Dr Pickles.

9.24 MAFF did, indeed, react to the recommendation. According to Dr Pickles, Mr Lawrence went white when he read it. ¹⁰ He informed Mr John Suich, to whom he reported in Animal Health Division, of what was proposed. In January 1989 he, in his turn, sent a note to Mr Andrews, copied to Mr Meldrum, commenting:

BSE is thus being used as a peg on which to hang a controversial recommendation which goes far wider than Professor Southwood's remit. If implemented it would have serious consequences not least for the rendering industry, which processes over 100,000 tonnes of raw material every month, thus providing a source of animal feed and industrial raw material, and also a 'waste disposal' service for the slaughtering industry . . .

The Secretary may wish to consider what, if anything, should be done in the meantime or at the [3 February] meeting itself. I would suggest that, at the very least, the members of the Working Party should be made aware of what the rendering industry does and its scale of activity so that they can reflect on the implications of the draft recommendation. A MAFF paper could be prepared to achieve this. The Secretary may also feel that a senior member of the SVS [State Veterinary Service] should offer to attend the meeting to amplify the information if necessary and to answer points raised by the Working Party. ¹¹

9.25 Mr Andrews discussed the proposed conclusion with the Minister, Mr John MacGregor, and it was agreed that MAFF should place before the Southwood Working Party a document setting out the practical and economic implications of the proposal, and offering that Mr Meldrum should attend the Working Party to explain the issue in more detail. Manuscript notes on a minute outlining this proposal demonstrate the strength of feeling at MAFF. Of the proposal that Mr Andrews should offer the Working Party the assistance of Mr Meldrum, Mr Donald Thompson wrote 'insist if we can' and added this comment: 'I cannot say how strongly I regard this matter. Of course we must take all due care but the environmental, economic and the competition consequences would be dire if Prof. S was to go forward.' ¹²

9.26 Meanwhile, on 16 January 1989, Dr Martin had written to Sir Richard, drawing attention to the problem of disposing of animal waste and suggesting:

Rendering and recycling, despite its limitations, would seem to be the most acceptable method at present. Provided the rendering is carried out in a satisfactory manner at sufficiently high temperature to destroy all pathogens then it becomes less objectionable . . . I think we have to be restrained in the view we express in the report, on this subject. ¹³

9.27 A memorandum on rendering was duly submitted by MAFF to the Working Party setting out the waste disposal implications if meat and bone meal could no longer be fed to animals. The offer by Mr Meldrum to attend to give additional assistance was politely declined by Sir Richard.

9.28 The Working Party held their final meeting on 3 February 1989. Before the meeting Mr Lawrence managed to speak to Sir John Walton and Dr Martin about the implications if the practice of rendering were to cease. In his note of the final meeting, he reported:

In response there was a clear statement from Sir Richard Southwood that it was not the Working Party's intention to recommend that rendering should cease, or even that animal protein should not be used in feed rations. Rather that the processes used must ensure that organisms which can cause disease are destroyed in the cooking process. As a result paragraph 9.4 has been amended. ¹⁴

9.29 The amended passage read as follows:

9.4. . . . we believe that the risks from inadequately sterilised animal products are such that this method of disposing of animal waste should be changed so as to eliminate these novel pathways for pathogens.

9.30 The meaning of this was further clarified by Sir Richard at a meeting on 14 February 1989 with Mr John MacGregor and others. The minute records:

Sir Richard said that he was not merely concerned with cattle and goats but also with other animals such as pigs and poultry (although the problem was much less here since they were scavengers). We either had to find a rendering process capable of producing a more sterile result (ie, the destruction of all pathogens) or we should consider finding other ways to dispose of the animal products (although this last point was not something he would say in public). When asked by Mr Meldrum whether he was saying that meat and bone meal should no longer be fed to pigs, Sir Richard replied that this was a matter for the vets and not a matter on which he would want to advise. ¹⁵

9.31 The Working Party explained to us that:

Recognising the practical problem of disposing of extensive quantities of MBM, we did not recommend extending the ban to pigs and poultry. Prior to 1990 these animals must have been exposed to food with MBM prepared from offal; a spongiform encephalopathy has never been reported as naturally occurring in these farmed species. ¹⁶

9.32 The Report ended with a Summary, which was drafted by Dr Pickles. The following passage appeared in it:

10.4. Concerned at the remote chance that this new infection could be transmitted orally to man, we recommended the destruction of carcasses of cattle with suspected BSE . . . and prohibition of the use of milk from such cows for humans . . . These recommendations have already been acted upon.

9.33 Mr Lawrence subsequently reported:

. . . there had been some suggestion that a recommendation should be made in relation to exports of meat and bone meal. However, the Working Party was persuaded not to include such a recommendation because importing countries were well aware of our health status and it was therefore up to them to decide whether or not to import and under what conditions. ¹⁷

9.34 Individual members of the Working Party nonetheless subsequently expressed concern at the fact that Great Britain continued to export meat and bone meal. Thus, in a letter to Sir Richard on 16 November 1989 Professor Epstein commented:

I was not very happy to hear that bone/meat meal containing presumably infected sheep/cow material is being fed to pigs in UK and also exported to countries where it may be fed to cows, but what can one do? The CVO from the Ministry was not very helpful on this point. ¹⁸

9.35 Dr Pickles was also concerned about this. She wrote to the CMO on 6 February:

There is, however, one loose end I would like to bring to CMO's attention. The small export trade in meat and bone meal is expected to increase now use is curtailed in the UK. There is no warning that this meat and bone meal is not regarded as fit for feeding to ruminants in the parent country. Whilst feeding of concentrates to cows is not as widespread on the continent as in the UK, it does take place. If neither Sir Richard nor MAFF are proposing any action on the understanding it is up to each country to protect the health of its own animals by whatever means they feel appropriate, perhaps CMO might like to alert his opposite numbers in Europe. ¹⁹

9.36 Dr Pickles's initiative was typical of her readiness to press any matters that concerned her, even though this might strictly have fallen within the responsibility of others.