Volume 3: The Early Years, 1986-88
3. Epidemiology
Covert investigation of the feed theory

3.18 On 15 December 1987 another meeting was held at Tolworth, chaired by Mr Rees, at which Mr Wilesmith was present. The note of the meeting records:

Studies appear to show that there may not be a genetic link in relation to this condition. However, there was some evidence that feed (meat and bone meal including material from sheep) might be a factor. ¹

3.19 This significantly understated the position. Mr Wilesmith told us that by this stage he was sufficiently confident that BSE was associated with a feed-borne source and that there was no longer any need to canvass some of the other possibilities in the questionnaires that were addressed to affected farms. Commercial concentrates, either as finished rations - such as pelleted calf feed and dairy cow cake - or as protein supplements used in home-mixed rations, had been fed at some time to all the cases for which accurate records were available. ² Mr Wilesmith concluded that the source of infection was most likely to be meat and bone meal (MBM), although other animal-derived products such as blood and tallow could not be excluded at that stage. ³

3.20 Mr Rees told us that by 15 December 1987 they were fairly sure that MBM was indeed the cause. ⁴ The note of the meeting goes on to record that it would be useful to have more information from the feed industry and that Mr Keith Meldrum (at that point Director of the Veterinary Field Service) would arrange an 'off-the-record' meeting with his contacts.

3.21 Mr Wilesmith prepared a report covering the period up to the end of December 1987: 370 clinically suspected cases had been reported on 237 farms. Of these, 132 cases on 113 farms had been histopathologically confirmed. Completed questionnaires had been received for 90 of these herds. The source of the commercial dairy concentrates used was recorded for 60 of those herds. No single compounder was common to all herds. Mr Wilesmith commented:

Although epidemiological findings support the introduction of a transmissible agent via cattle feedstuffs, it is not obvious, at the present time, how and why this has occurred. The most likely vehicular constituent of cattle feedstuffs is meat and bone meal or other animal derived products such as tallow or blood. Meat and bone meal has been used in cattle feedstuffs for some time usually at an inclusion rate of 3-5%. The analyses of data, in progress, arising from surveys of the composition of cattle feedstuffs will provide evidence of changes in this inclusion rate. At present it is not possible to determine whether the exposure of cattle to a foodstuff-borne agent was for only a short period or is continuing. The studies in progress will assist in this respect. ⁵

A footnote to the report emphasised that:

The abstract should not be entered on the database. There must be no possibility that the feedstuffs industry becomes aware of the current hypothesis. ⁶

3.22 We were puzzled by the reticence shown by MAFF officials in making confidential enquiries rather than a direct approach to UKASTA for assistance. Mr Rees in his written statement to the Inquiry said:

The investigations into the origin of BSE infection were concentrating on contaminated meat and bone meal ('MBM') and tallow in feedingstuffs as being the possible vehicle of infection. In order to find out more about the use of MBM and tallow, the co-operation of the feedingstuffs industry was needed. Advisers to the feedingstuffs industry were very reluctant to assist at first, because of their need to keep the commercial confidence of the various companies they worked for. However, in these early stages we did manage to have some very informal discussions with a few advisers who we knew on a more personal basis, to determine the extent of the use of MBM in commercial feedingstuffs, and the distribution of MBM. These were really very informal chats as no one wanted to meet formally with MAFF at this stage. I was hoping I would eventually be able to persuade the industry to help MAFF more formally in the future. ⁷

3.23 When we pursued this with Mr Rees in oral evidence, it transpired that any reluctance on the part of the feed industry to assist MAFF was more apprehended than real. Mr Rees told us of a single conversation that he had, on a personal and confidential basis, with an adviser to a feed manufacturer. While willing to assist, the adviser was not able to give very sound information as to the content of animal feed four or five years in the past, which was when Mr Wilesmith had calculated most instances of infection must have taken place (see paragraph 3.28 below). ⁸

3.24 We asked Mr Meldrum why it had been agreed that he would meet his contacts on an 'off-the-record' basis. He explained that Mr Wilesmith's attribution of the cause of BSE to meat and bone meal was only a preliminary view:

When you are dealing with a very early investigation or some very early reports, it is better to keep the investigation to yourself and release the information in a proper and reasoned and planned way when it becomes substantive. ⁹

3.25 Mr Meldrum told us of a detailed discussion that he had with Mr Paul Foxcroft of Prosper De Mulder (the leading renderer in England and Wales) about current rendering practices. ¹⁰ It may be that he did not disclose the reason for his interest, or it may be that the conversation took place a little later in the story. Either way, Mr Foxcroft informed us that he was absolutely certain that he was not aware of any suggestion of a link between BSE and animal feed until March 1988. ¹¹

3.26 Early in January 1988 Mr Wilesmith and Mr Meldrum had a meeting with Dr Laurson-Jones, a veterinarian who had worked for BOCM Silcock (a feedstuff manufacturer), and Mr Mike Stranks of the Bristol regional office of ADAS. Each confirmed that significant amounts of UK-produced MBM were included from time to time in compound rations of both calves and adult cattle. ¹²

3.27 On 17 December 1987 Mr Wilesmith had asked Mr Gallehawk, of the Statistical (Agricultural Commodities) Division of MAFF, for information on the composition of commercial cattle feed over the previous ten years. The data that he supplied showed that there had been no increase, or new use of MBM, in cattle feed between 1979 and 1987. ¹³ This information gave no indication of any new factor to explain the emergence of BSE at the end of this period. An important question in this context was the date at which cattle were first subjected to infection. This was a matter to which Mr Wilesmith had been giving consideration.

3.28 By the end of 1987 there had been a sufficient number of victims of BSE to enable Mr Wilesmith to carry out what he described as 'relatively simple simulation studies' based upon the age-specific incidences of BSE. He assumed that the incubation period had a log normal distribution, in line with common incubation periods for infectious diseases. Applying this assumption, the simulation suggested that effective exposure of the cattle population was likely to have begun in the winter of 1981-82 and continued until the end of 1984 at least, and that the risk of effective exposure was considerably greater for calves than adults. Calves were either exposed to more of the infectious agent or more susceptible to the exposure, or a combination of both. ¹⁴

3.29 The results of these studies led Mr Wilesmith to look for some change or changes of exposure in or about 1981. The data received from Mr Gallehawk appeared to rule out any change in diet at this time, ¹⁵ which led him to consider whether any of the processes in the animal feed industry had changed at the relevant time.

3.30 As to these, Mr Gallagher of the Starcross VIC had been making enquiries about processing at a large renderers in Exeter, which formed part of the Prosper De Mulder Group. He reported that the plant received a large intake of sheep material from both south-west England and South Wales from which an average weekly production of 200 tonnes of MBM was extracted. The temperatures reached during the processing would not destroy the scrapie agent. Distribution from the plant was widespread, although a large bulk was taken up by compounders in the South West. ¹⁶

3.31 Mr Gallagher ended his report with the observation that, clearly, a central initiative to the industry was the next step. ¹⁷ Mr Wilesmith had reached the same conclusion. In a note to Dr Watson dated 14 February 1988 Mr Bradley stated that Mr Wilesmith now had enough data to go to the industry with specific questions to answer about feed. He added: 'Clearly this needs delicate handling.' ¹⁸

3.32 Meanwhile, at the end of January 1988 Mr Wilesmith received some information which tended to confirm his hypothesis that MBM was the source of infection of BSE. In July 1986 a nyala at Marwell Zoological Park in Hampshire had succumbed to a scrapie-like spongiform encephalopathy. In June 1987 a gemsbok succumbed to a similar condition in the same zoo. Investigation showed that between March 1986 and March 1987 the pelleted antelope diet in use, manufactured by Bockley Mills, contained a meat-based product supplied by Prosper De Mulder in Exeter. ¹⁹

3.33 MAFF officials set out the position with a degree of caution in a submission sent by Mr Andrews (MAFF Permanent Secretary) to the Minister, Mr John MacGregor, on 24 February 1988. This stated:

Although it is not possible to draw conclusions from the work carried out so far a plausible hypothesis is that BSE may be caused by an unconventional transmissible agent which could have been introduced into affected animals through feedingstuffs derived from the carcasses of animals such as sheep which are known to be susceptible to encephalopathies. ²⁰

3.34 Mr Andrews added this comment in a covering minute:

There are a number of reasons for thinking the disease may have originated from some change in feeding practice, possibly as a result of the incorporation of animal residues in feedingstuffs. This line of inquiry is being explored and I am sure that we need to pursue these investigations urgently in order to decide whether some action should be taken to modify the ingredients in animal feedingstuffs. ²¹

3.35 On 26 February 1988 Mr Wilesmith produced a report on his investigations to date. This explained that the only relevant factor common to all BSE cases appeared to be that commercial concentrates were fed to the adults in all affected herds, although no one compounder was common to all herds. In respect of calf feeding, some form of concentrate was the regime in all but one farm. He concluded:

The finding of scrapie-associated fibrils (SAFs) in a proportion of histopathologically confirmed cases is undoubtedly significant in terms of the aetiology; SAFs have only been observed in encephalopathies associated with transmissible agents. The absence of any evidence from the epidemiological investigation of other sources of such an agent together with the occurrence of a common source epidemic strongly suggests the introduction of an infectious agent via commercial cattle feedstuffs. ²²