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?
