Volume 11: Scientists after Southwood
4. The Spongiform Encephalopathy Advisory Committee (SEAC)
Deliberations and advice
4. Advice on animal feed

4. Advice on animal feed

4.287 We noted earlier, in the context of SEAC consideration of the 'safety of beef', the emergency meeting of SEAC held on 17 May 1990 to discuss the implications of the first case of a spongiform encephalopathy in a cat. The minutes record that the Committee asked for consideration to be given to pig and poultry feed at the next meeting. ¹ This led Mr Gummer to decide that SEAC's advice should be sought on the practice of including animal protein in animal feed. Mr Andrews commented that the issue would have to be very carefully handled and that it would be appropriate for the Department to provide a background paper explaining its present policies and the reasons underlying these. ²

4.288 Mr Gummer and Mr Andrews identified three principle issues to be put to SEAC: first, the question whether there should be a ban on the feeding of any animal protein to ruminants; second, whether the feeding of any animal protein to any animal should still be permitted; and third, whether there should be a ban on the inclusion of specified bovine offal in pig and poultry feed. ³ They agreed that it would be appropriate for the Department to provide a background paper explaining present policies and the reasons underlying these. As regards implementation of any measures arising from SEAC: 'Our powers to act would depend upon the terms of the advice given by the Committee. The question of whether action was taken for health reasons or because of public sensitivity was crucial.' ⁴

4.289 At its meeting on 13 June 1990, SEAC had before it a paper prepared by MAFF's Animal Health Division entitled, 'Spongiform Encephalopathies and other Species: Pigs and Poultry'. ⁵ The paper referred to the pressure to extend the SBO ban to animals, and noted that the Government had 'resisted calls to extend the scope of the ban in the firm belief that there is no scientific justification for such action'. It explained that this view was based on the conclusions of the Southwood Report that non-mammalian species were unlikely to be susceptible to BSE, scrapie or any spongiform encephalopathy, and on the absence of any record of pigs getting a TSE. Kuru had not proved to be experimentally transmissible to pigs. The paper went on to explain the value of MBM as a source of protein. It gave details of transmission experiments of BSE to pigs, with negative results after 16 months.

4.290 Minutes of the meeting record that the Committee agreed that the question of feeding ruminant material to pigs and poultry needed further study. Points for consideration were that pigs would have received the same exposure to the BSE agent as cattle, that most pigs were slaughtered before the disease was likely to express itself, and that bovine material in the gut contents of slaughtered pigs might be used in MBM fed to cattle. However, it was felt that the probability of the agent being recycled back into cattle was small. ⁶

Agriculture Select Committee's inquiry into BSE

4.291 On 10 July 1990 the House of Commons Agriculture Select Committee's Fifth Report on BSE was published. The Committee noted the Minister's resistance to making the PFMA's voluntary ban on the inclusion of SBO in pet food statutory, and stated that 'in this instance, which is not one of pure science but political judgement, we take the opposite view'. The Committee thought that:

. . . with a disease as distressing as BSE, people are entitled to expect that the food they feed their pets should be protected by the same basic legislative safeguards as their own food, particularly in view of the uncertainties surrounding the newly identified feline encephalopathies.

It therefore recommended that the PFMA's voluntary ban on SBO in pet food be made statutory. ⁷

4.292 The Committee also dealt with the proposal for a statutory ban on feeding cattle offal to pigs and poultry, and stated that it was a view with which it had some sympathy. It noted that MAFF had resisted a statutory ban due to a lack of scientific evidence, and then commented on UKASTA's voluntary ban:

We understand the reasons for this measure which are, first, to maintain public confidence and, secondly, to insure against the remote possibility that BSE is transmissible to other species; and we trust that, in judging how long to keep it in force, the industry will be guided by the latest scientific evidence. ⁸

4.293 Whilst the Committee felt that it had not taken enough evidence to reach firm conclusions of its own, it advised that the Government should establish an expertcommittee to examine animal feeds and advise on the need for industry regulation.This led to the establishment of the Lamming Committee in 1991. ⁹

Experimental transmission of BSE to a pig: SEAC recommends an animal SBO ban

4.294 On 16 August 1990, Mr Lowson submitted to Mr Gummer a paper, to be put to SEAC at its meeting on 19 September 1990, on the inclusion of SBO in feed for non-ruminants. The paper quoted the Southwood Report's conclusions in relation to pigs, poultry and pets - essentially that no action was called for other than research. It gave details of unsuccessful efforts to transmit kuru to poultry and to pigs. It also described the CVL's experiment to transmit BSE to pigs, which had to date produced no positive results. The paper set out by way of summary and conclusion:

Although cats have succumbed to a spongiform encephalopathy, and have been infected experimentally with CJD, no major pet species, pigs or poultry have been shown to be susceptible to spongiform encephalopathies transmitted by ruminant material, even by intracerebral inoculations, and there is no significant evidence of pigs, poultry or dogs having been infected with any scrapie like disease. Pigs and poultry will have been exposed to the BSE agent over as long a period as cattle have been, without succumbing to the disease, and the total quantity of agent in the specified offal is now likely to be on a downward trend. There is wide scope for pet owners to avoid any material which they consider unsuitable, in spite of the absence of evidence.

There does not therefore seem to be any current evidence on which to take the view different from the Southwood Working Party's. This position would need to be reassessed if there was evidence that the inclusion of material derived from specified offals in pig and poultry feed or pet food was substantially higher than before the offals ban was introduced, but that is certainly not the case at present.

The Committee is invited to endorse these conclusions. ¹⁰

4.295 The paper was overtaken by the events that we now turn to describe.

4.296 On 20 August 1990, a positive result was recorded in the CVL's experiment to transmit BSE to pigs. One pig had been diagnosed by post-mortem pathology as having developed a spongiform encephalopathy. A confidential pathology report submitted by Mr Gerald Wells, Head of the CVL's Neuropathology Section, to his colleague Mr Michael Dawson in the Virology Department, included the following remark:

The result, albeit confined to one animal in the experimental challenge group is incontrovertible evidence of the transmissibility of BSE to the pig by simultaneous intracerebral, intravenous and intraperitoneal inoculation routes. ¹¹

4.297 Mr Meldrum told the Inquiry that he decided that the discovery should be kept confidential until SEAC had had an opportunity to review and discuss it, although he informed the Minister, Mr Gummer, by telephone as soon as the preliminary results were known and they discussed the matter via video link. ¹²

4.298 On 23 August 1990, Dr Pickles reported the discovery to Sir Donald Acheson. Her minute noted:

CMO should be aware that a pig inoculated experimentally (i.c., i.v. and i.p.) with BSE brain suspension has after 15 months developed an illness, now confirmed as a spongiform encephalopathy. This is the first ever description of such a disease in a pig, although it seems there are no previous attempts at experimental inoculation with animal material. The Southwood group had thought pigs would not be susceptible. Most pigs are slaughtered when a few weeks old but there have been no reports of relevant neurological illness in breeding sows or other elderly pigs.

An urgent meeting is being called of [SEAC] but since key members and the chairman are now overseas at a meeting this may not be until the week beginning the 3rd September. Points for consideration:

(i) In view of the long term exposure of pigs to scrapie without ill effect, does this suggest the species range for BSE is wider than that of scrapie, and if so what are the implications?

(ii) Should the feeding of ruminant protein including BSE and scrape-infected offal to pigs now be discontinued?

(iii) Is any action needed to protect humans, eg extending the offal ban to pigs?

For information, there are now 9 cats confirmed with feline spongiform encephalopathy, suggesting this is indeed a new disease and exposure to BSE unlike exposure to scrapie has been hazardous for cats.

Mr Maclean was informed last night and has agreed an early meeting of [SEAC] is required to give advice on which decisions will be made. In the meantime, he does not want to go public. Mr Maclean is expected to advise Mr Gummer. In these circumstances, CMO might like to consider whether [Mr Dorrell] should be informed. ¹³

4.299 Sir Donald Acheson informed Mr Dorrell of the diagnosis of the pig on the same day:

While this clearly is a cause for concern we should not jump to the conclusion that this means that pigs will necessarily be infected by bone and meat meal fed by the oral route as is the case with cattle. An important point to take into account is that it appears that brain material from sheep infected with scrapie has never been experimentally injected into pigs and it may well be that pigs would also be infected by this route.

At the moment there is insufficient information on which to base any further action. In particular I do not think that it is necessary for the Medicines Control Agency or the Procurement Directorate to take any action about porcine materials. The next step should be to await the result of discussions at the next meeting of the Tyrrell Committee which will be held early in September. I have discussed the matter with Professor David Tyrrell and he agrees. Mr Maclean has been advised of the situation. ¹⁴

4.300 A meeting of SEAC was called at short notice on 7 September 1990 to consider the implications of the experimental results. A paper prepared by Mr Meldrum was before the Committee which considered the preliminary results of the experiment, and considered whether as a consequence any changes should be recommended in relation to animal and health controls. The paper outlined the experiment results noting that:

The Committee will wish to consider whether the transmission of BSE to one pig under challenging experimental conditions alters our scientific knowledge of the disease to an extent whereby additional animal or public health control measures should be recommended to Ministers. ¹⁵

4.301 In relation to the animal health implications the paper noted:

15. The Committee will also wish to consider whether there is any need to make recommendations for further action relative to the animal health implications of BSE. There are a number of options:

Do nothing

16. The argument would be that the result is not a surprising one, given the weight of challenge and method used. It is a laboratory experiment and is quite different from the position in field conditions. For instance, the oral route of transmission is less efficient than the parenteral route by a factor of 105 (Kimberlin and Walker, 1983). The monitoring of the adult pig herd nationally has not been revealed any case suggestive of a scrapie-like sub-acute spongiform encephalopathy. Furthermore, most pigs are slaughtered at under seven months. Thus, even if transmission were possible through the feed route, the vast majority or animals would be too young to pose any risk.

Legislate to ensure that meat and bone meal derived from specified offal cannot be used in pig rations

17. Many industry and consumer organisations have advocated that the Government should legislate to prevent the use of processed specified bovine offals in pig and poultry rations and, indeed, in pet (dog and cat) food. The Government's response has been to point to the lack of scientific evidence to warrant such a course. Clearly the situation has changed in that, for the first time, a transmissible spongiform encephalopathy has been recorded in a pig. Although the range of scientific and other arguments and counter-arguments do not, perhaps, point to this measure being necessary on strict scientific grounds or at least until more evidence becomes available from transmission studies, it would, in practice, simply add the weight of legislation to an arrangement which is already operating, de facto on a voluntary basis. This is the option that holds most attraction for the Ministry's veterinary advisers and would ensure that bovine offals that are not permitted to be used for human consumption are not used in the food of livestock or poultry either. Such action might defuse a situation in Germany whereby guarantees are now being sought that imported pet food does not contain any bovine material of UK origin.

Ban the use of ruminant-based meat and bonemeal as a feed ingredient in pig rations

18. This would represent the most radical solution. It would deal not only with concerns about BSE agent being re-cycled to pigs, but also the continuing exposure of pigs to the scrapie agent from sheep. The logic of such a course would, almost inevitably, require that such rations are also banned from use in other livestock - poultry and horses and also in pet food. In the latter case the evidence from the investigations arising from the ten cats which have succumbed to a spongiform encephalopathy is that we are probably witnessing a new disease in cats. However, it could be argued that pursuing such an option would be over-reaction since there is no evidence of a porcine encephalopathy under natural conditions and it is possible that pigs are not susceptible to BSE by the oral route but only when presented with a massive challenge.

19. The consequences of following this option are very serious indeed. There would be major repercussions for the rendering industry, which would reverberate throughout the agri-food cycle. There is currently no practical or viable alternative use for the 400,000 tonnes of meat and bonemeal which is produced annually. This would mean that it would have to be buried or incinerated after processing. Cost estimates put this at about £70 million using burial and £150 million using incineration. It would mean an increase of something between 1p-2p per pound of meat. But it is unlikely that all this additional cost would be borne by consumers. Even if it were, it would only have a small impact on the retail price index. This, in turn, would put further pressure on the meat market and place the UK industry at a competitive disadvantage even though we have in place far more comprehensive control measures than any other country. There would also be some spin off in Europe making it more difficult to export pig meat as the public would perceive such action as tantamount to an admission that pig meat presented a public health hazard.

4.302 At its meeting, SEAC accepted CVL's conclusion that the experimental result provided 'incontrovertible evidence' of the transmission of BSE to pigs. The points emphasised by SEAC included:

1. the pig had become infected after receiving a massive dose of BSE infected material by a highly efficient route, ie, intracebral, intraperitoneal and intravenous inoculation with brain tissue from cattle affected with BSE;
2. the clinical symptoms shown by the pig could not have been easily confused with those of any other condition and it would be unlikely that more than an occasional case had occurred and gone unnoticed in the field; and
3. many questions remained unanswered; for example, would smaller doses cause disease, would large doses given by mouth be effective and would scrapie produce spongiform encephalopathy in pigs under similar conditions? ¹⁶

4.303 The minutes of the meeting record that:

It was very difficult to draw conclusions from one experimental result for what may happen in the field. However it would be prudent to exclude specified bovine offals from the pig diet.

Although any relationship between BSE and the finding of a spongiform encephalopathy in cats had yet to be demonstrated, the fact that this had occurred suggested that a cautious view should be taken of those species which might be susceptible. The 'specified offals' of bovines should therefore be excluded from the feed of all species. ¹⁷

4.304 The Committee noted that pigs and other species would have been exposed, for many years, to material from scrapie infected sheep without apparently developing a spongiform encephalopathy. As a consequence they concluded that 'there were no grounds for extending the ban on the use of ruminant protein to non-ruminants, providing the specified bovine offals had been excluded'. ¹⁸

4.305 In general, the Committee felt that 'there were no implications for human health in the fact that a pig had shown itself susceptible under laboratory conditions'. The Committee stated that if there were a hypothetical risk, it would be greatest where porcine tissues likely to contain the agent were used in preparations which were injected or implanted into human beings or livestock. They recommended that this possibility should be brought to the attention of the Medicines Control Agency, the Medical Devices Directorate, and the Veterinary Medicines Directorate. This matter was discussed by the BSE Working Group and is discussed in vol. 7: Medicines and Cosmetics.

4.306 On 14 September 1990, Mr Lowson put a submission to Mr Gummer setting out the proposed action in light of experimental transmission of BSE to a pig. ¹⁹ He noted that SEAC were due to meet in the following week to finalise their advice. He said:

They can be expected in particular to recommend that the specified [bovine] offals excluded from human consumption and protein derived from them, should be banned for use in feeding to animals as well. A separate submission will be coming forward seeking Ministerial approval to an Order which achieves this. The aim will be that it should come into force as soon as the decision is announced. ²⁰

4.307 It continued:

A ban on the use of specified offals in animal feed will no doubt lead to claims for compensation from the Industry, as it will effectively make meat and bone meal derived from them unsaleable . . . It is therefore recommended that when this point is raised we should take a negative line. Nevertheless the ban can be expected to lead to further costs being passed onto slaughtering and livestock industries by renderers and knackers.

Consultation has so far been restricted to a very limited circle. However as the ban on the use of the specified offals for animal feed will apply throughout Great Britain, and will need to be mirrored in Northern Irish legislation too, I hope that the Minister will agree to our telling colleagues from the other Agricultural Departments about what is happening. We will also, if the Minister agrees, set up a meeting for interested industry organisations as soon as the information is released. ²¹

4.308 SEAC issued formal advice on 20 September 1990, following its meeting on the previous day. The advice stated:

Since this result shows that pigs can get spongiform encephalopathy, even though there is no evidence that they have done so in the field, we believe that pigs should no longer be fed with protein derived from bovine tissues which might contain the BSE agent, ie, those 'specified' bovine offals that are already excluded from human consumption. It would make sense to extend this prohibition to feed for all species, including household pets, as other species have now developed spongiform encephalopathies. We are aware that many animal feed compounders and pet food manufacturers are already applying such a ban on a voluntary basis. ²²

4.309 In a statement to the Inquiry, Dr Tyrrell said:

It was the rapid increase in the BSE epidemic, the occurrence of more cases of FSE and the results of the pig transmission experiment which led SEAC to give the advice we did on the extension of the SBO ban. Before then (September 1990), we were not asked to advise on the extension of the SBO ban.

It was important to consider humans before other animals. It should be remembered that prior to the test results of the pig transmission experiment, pigs and poultry were not known to be susceptible to TSEs. Breeding pigs, in particular, were thought to have received a very high exposure to the same type of contaminated MBM as cattle but without any evidence of the occurrence of TSE. The issue of symptom-less hosts was considered very carefully because it could apply to all domestic and farmed animal species. ²³

4.310 Mr Meldrum concurred that the result from the pig experiment had also changed the landscape for MAFF:

It was not until . . . August 1990, that the result from the pig persuaded both SEAC and us to change our view and to take out of pig rations any residual infectivity that might have arisen from the SBOs. ²⁴

Discussion

4.311 Policy decisions in relation to the practice of incorporating animal protein in animal feed called for a number of factors to be weighed in the balance. On the one hand was the risk that this practice might result in the transmission of the BSE agent. On the other hand were the following facts:

• Converting animal offal into animal feed was a large and profitable industry.
• Converting animal offal into animal feed solved what would otherwise be a massive and costly waste disposal problem.

4.312 Until the experimental transmission of BSE to a pig, MAFF officials and Ministers were in no doubt as to how the balance tilted. Experience strongly suggested that pigs and poultry were not susceptible to TSEs. There was no justification for the costs that a ban on the use of SBO for non-ruminant feed, let alone a total ban on feeding animal protein to animals, would involve.

4.313 The Southwood Working Party had shocked MAFF officials when they appeared to be challenging the practice of feeding animal protein to animals. They, and their Ministers, were anxious that SEAC should not advise against this practice without appreciating fully the implications of doing so. It was for this reason that Mr Andrews remarked that the issue would need to be carefully handled. No doubt it was for this reason that the paper for SEAC dealing with the issue was submitted to Mr Gummer himself for approval.

4.314 The paper prepared for SEAC had annexed to it a paper on the rendering industry describing the 'crucial service' that it performed for abattoirs and the value of the industry. The paper set out in detail MAFF's reasons for concluding that BSE was not transmissible to pigs or poultry and invited SEAC to endorse their conclusions.

4.315 It seems to us that this manner of approaching SEAC came close to delegating to SEAC the policy decision. SEAC was in a position to offer expert advice on the likelihood that BSE might be transmissible to non-ruminant animals. Whether that likelihood would justify the consequences of an SBO ban, or a total ban on feeding animal protein to animals, was essentially an issue for Government in the light of SEAC's expert advice. It was something that could profitably have been discussed with SEAC in a dialogue. This would have been a preferable course to advancing their case on paper for SEAC to accept or reject.

4.316 In the event, the draft paper was overtaken by the experimental transmission of BSE to a pig. It is interesting that at that point, the MAFF veterinarians submitted a paper advancing as their preferred option a ban on incorporating MBM derived from SBO in pig rations. MAFF officials' previous line had been that experimental transmission to a pig would not justify this step. Once again SEAC was asked to take the policy decision, with a very firm steer from MAFF.

Feeding porcine MBM to cattle

4.317 In September 1992, MAFF received a report that a company was looking at the feasibility of producing porcine meat and bone meal to sell for incorporation into cattle feed. ²⁵ The Minister's view of this was that 'we should not take a neutral line, but should actively discourage, and be seen to discourage this practice'. ²⁶ As neither the Lamming Committee nor the Tyrrell Committee had identified the feeding of pig material to ruminants as a matter that required action, SEAC was asked to consider this question at its next meeting on 15 October 1992. ²⁷

4.318 SEAC advised that:

While there was at present no way of assessing the risk that the use of porcine material in cattle feed might lead to the transmission of an SE agent, and while it was reasonable to assume that any risk was low, it was not possible to say there was no risk. The Committee noted that in practice porcine material was not being fed to cattle and felt that it was advisable for this situation to continue. ²⁸

4.319 At its next meeting, on 22 April 1993, SEAC was informed that MAFF Ministers had accepted the advice that porcine protein should not be fed to cattle. MAFF felt that a statutory ban was unnecessary but the industry would be told that legislation would be introduced if there were any indications that such material might be used in practice. ²⁹

Discussion

4.320 It is not easy to follow the precise nature of risk evaluation that led to Mr Gummer's reaction or SEAC's endorsement of it. We suspect that the former was a broad reaction against reinstituting the 'unnatural practice' of feeding animal protein to ruminants and that SEAC were happy to endorse a precautionary approach that did no more than continue the existing position.