witness statement

name: Stephen Dealler
section: Food Poisoning
for: The Defence
experience: Medical Microbiologist


The witness in his capacity as a medical microbiologist provides essentially what is a scientific report on the issues surrounding BSE and the risk posed to humans. The statement is uncompromising in its stance.

It was therefore known at that time that a risk was present to humans and that the calculation of this risk was currently impossible.


Not available for this witness

Full cv: (not available for this witness)

full statement:

Concerning the Development of Bovine Spongiform Encephalopathy. It is thought that the presence of pesticides in the tissues of bovines may be a contributory factor to the outbreak of BSE in the UK.

The worry is that the pesticides (in this case organophosphate insecticides) may act on the animal tissues to produce a transmissible spongiform encephalopathy, which may in turn be a risk to human health.

Proof for this is not available at this point and research into it is continuing.

Investigation is underway into the medical ethics of whether things that are not adequately certain to be safe to humans should be banned. This is particularly important here in that, should BSE (or the insecticides that may be associated with it), cause a fatal human disease as a result of eating beef products, probably after the year 2000, the action necessary to prevent it could only have been taken before there was proof that this would happen, i.e. while there was no certainty of the safety of the food. I will try to give a better description of this below.

In medical practice, drugs and actions must be shown with specific animal and human tests to be either:

  1. not a risk to humans at all or

  2. of adequate advantage that this outweighs the risk to humans. While such evidence is not available the drugs or actions are assumed to be too great a risk to be acceptable.
The reason for this assumption is that very large numbers, indeed a large section of the population, receive certain drugs (etc). If a drug should turn out to be fatal then this would be such an enormous catastrophe (e.g. thalidomide) as to be unacceptable as a risk. The same ethics applies to food additives (and, presumably artificial chemicals present in foods), and they, as a result are treated in the same way by various foreign governments (e.g. the Food and Drugs Administration in the United States). In the UK it is not clear how ethical decisions are made concerning these chemicals in food.

The major problem with BSE is that there is no evidence that BSE will not infect humans to produce a similarly untreatable, undiagnosable, fatal disease (indeed we can estimate that there is a 70% chance that humans could be affected). The ethical question about this is as to whether such a large part of the population should be put at risk of a fatal disease before evidence is available that humans are not at risk. This question is the moral one that was being considered widely in 1988- 1991 and would not have required MAFF direction.

supplementary statement:

Concerning Bovine Spongiform Encephalopathy and its relevance to beefburger production.

  1. BSE became known to the Central Veterinary Laboratory in 1986 and had not been diagnosed in the world previously. In 1993 there were over 36,000 cases.

  2. This type of disease (called a transmissible spongiform encephalopathy or TSE) is known to be fatal, there is no treatment, there is no adequate method of diagnosis before death, they are passed from one animal to another by the eating of infected tissue.

  3. TSEs have been either found naturally or produced by experiment in over 48 species. At the time of the first report of BSE a TSE had been known in the same way in approximately 37 species, many of them monkeys.

  4. BSE has now been transmitted to 18 different species and 16 of them have been by the presence of the agent in food.

  5. In 1988 there has a Working Party on BSE (known as the Southwood Cormmittee) organised by the Ministry of Agriculture Fisheries and Food (MAFF) in the UK.

    At this time it was known,that infectivity was found in almost all tissues of an infected animal with a TSE but in some tissues in greater quantities than in others. It was also known that there was an approximately 70% chance that a TSE could be transmitted to any other particular mammal (i.e. if inoculated in some way into 10 different species a TSE would be expected to infect 7 of them.) It was also known that infectivity of tissue started early in the incubation period with peripheral tissues (liver, lymph nodes, spleen etc) and later, probably at half the incubation period for nervous tissue.

    Of the committee's major recommendations those relevant here were that no bovine brain be put into baby food, that clinically Infected animals be destroyed, that the feeding of cattle with potentially infected material be stopped, and that bovine material not be injected into humans.

    The committee decided that bovine brain/ spleen/ thymus/ liver/ gut/ lymphoid tissue/ bone marrow/ lung/ nerves were not a risk to humans as it decided that infected animals were being adequately destroyed, and that, as BSE was derived from scrapie in sheep (a reasonable presumption but without any evidence) and scrapie did not infect humans, neither would BSE.

    These aspects of logic were untenable at that time because:

  6. It was therefore known at that time that a risk was present to humans and that the calculation of this risk was currently impossible. Tyrrell would have been told this by any independent (i.e. external to MAFF employment) advisor.

  7. In 1989 an announcement was made by MAFF that the Southwood committee had not recommended adequately safe procedures and banned the presence of specific offals in humans (and later animal) food. This was introduced in November 1989 in England and Wales and in February 1990 in Scotland. Liver, kidneys, lung, bone marrow, nerves, all known to be infective in animals infected with a TSE were not included in this list of banned offals.

  8. In 1990 I published a scientific article calculating the potential risk to humans and showing it to be high but assuming specific levels of infectivity in tissue.

  9. In 1993 I published a more precise scientific article, fully based on MAFF data and published scientific facts, and using conservative assumptions, and standard epidemiological and mathematical techniques to calculate the risk to humans. This assumed that all cattle with disease were reported by farmers, that all cattle with BSE disease were diagnosed, and that BSE behaved like any other TSE. This showed to the risk to be unacceptably high.

  10. It also included calculations of the number of infected cattle that would have been eaten. I now know that this figure is about 1,800,000 cattle by the year 2000.

    Data were delivered in advance of publication to members of the Tyrrell Committee (the Spongiform Encephalopathy Advisory Committee).

  11. The action that McDonald's should, during the period relevant to this case, have taken concerning the risk from BSE to their customers is unclear currently as, although scientific data showed human risk to be ethically unacceptable, the repeated reports by the MAFF that the risk was 'minimal'.

  12. I believe that this is their current opinion despite data now indicating that BSE was not derived from scrapie, the numbers of infected cattle eaten being very large and that calves claimed earlier to lack infectivity have now been indicated (retrospectively) to have been infected (and eaten).

  13. It would only have been if McDonalds had sought independent medical advice concerning food safety that they should have received full warnings concerning BSE and its risk to humans. As far as I am aware there are very few people working on risks and epidemiology in the UK outside MAFF/Tyrrell Committee.

  14. It would only be between the appearance of the disease (1987) and the release of the Southwood Report (June 1989, although given to Government several months earlier), that McDonalds could not have taken action that was indicated by Government and might have sought external advice.

date signed: 10 Feb 1995
Reading of this statement in Court as evidence was dissallowed by the Judge
references: Not applicable/ available
exhibits: Not applicable/ available

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