Day 107 - 24 Mar 95 - Page 34


     
     1        or less?
     2
     3   MR. JUSTICE BELL:  Are we not back where we were early
     4        yesterday?
     5
     6   MR. MORRIS:  I just do not think we actually had a figure, or
     7        some kind of approximate figure, or percentage, of
     8        identifiable cases, whether rightly or wrongly, but a
     9        source has been identified?
    10        A.  To save time, if I may, I will answer very, very
    11        quickly because it can be disposed of very quickly.  The
    12        only way you get a source is when you have an outbreak.
    13        You cannot identify the sources by and large of the
    14        sporadic cases or of the family outbreaks.  So, you are
    15        talking about 200 general outbreaks where there may be
    16        sufficient evidence to track down the source.
    17
    18        My own work on that suggests that of those 200, the sources
    19        are reliably ascertained in less than 10 per cent. So, the
    20        number of reliable source reports is actually very, very
    21        small.  In fact, the authorities tend to rely on a less
    22        rigorous definition of source.  They make certain
    23        assumptions as to source very often.
    24
    25   Q.   So, of salmonella, for example, out of something between
    26        300,000 and 3,000,000, we are talking about, in your
    27        opinion, something like 30 or 40 might actually be
    28        successfully identified?
    29        A.  Yes.
    30
    31   Q.   Do those kinds of figures apply also to the other types of
    32        food poisoning that we have discussed with the beef and
    33        chicken products served by McDonald's, the risks?
    34        A.  Sorry, you have changed halfway through.
    35
    36   Q.   We are talking about salmonella.
    37        A.  In terms of source tracing?
    38
    39   Q.   Yes.
    40        A.  There are differences.  Salmonella is an extremely --
    41        salmonellosis is an extremely difficult, presents an
    42        extremely difficult epidemiological exercise because they
    43        are a multisource and the organism is widespread in
    44        the environment.  Take E.coli which so far has only one
    45        known source, one known source of any great significance,
    46        and is a very specific strain which is not
    47        widespread  -----
    48
    49   Q.   The one known source is?
    50        A.  Is cattle, although it has been found in pigs 
    51        occasionally.  But, so far, the predominance of the strain, 
    52        that particular strain, 0157, has been associated with 
    53        cattle.  Therefore, you are entitled to make certain
    54        assumptions as to source, so that if you find 0157 in, say,
    55        a beef product in a restaurant, you are fairly well
    56        entitled to say with a good degree of support that the
    57        source of that was cattle from whatever source.
    58
    59   Q.   And the other organisms that we have mentioned,
    60        campylobacter, listeria?

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