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20 March 2003
Food Standards Agency Review of OTMS:
a follow up
James Irvine
FRSE, DSc, FRCP(Ed), FRCPath, FInstBiol, FIsntDirectors
Teviot Scientific Consultancy, Edinburgh
Teviot Agriculture, Cultybraggan Farm, Comrie, Perthshire
Scotland
© Teviot Scientific Consultancy
Filed 20 March 2003
Earlier this month (12th March) Land-Care carried
an article by myself regarding the announcement by the Food Standards
Agency (FSA) that it was going to review the Over Thirty Months
Scheme (OTMS) whereby (with few exceptions) cattle over 30 months
old are prevented from entering the food chain (1).
In that article a number of questions were raised
for which Land-Care has sought some answers. The purpose of this
article is to make available to Land-Care readers the results of
our endeavours so far. Although some questions remain unresolved,
the information that has been forthcoming is quite informative in
some important aspects that at least I was not previously aware
of.
Land-Care e-mailed Professor Neil Ferguson and,
on his recommendation, also Professor John Wilesmith. We are grateful
to them for taking time to reply.
Information about the Basis for the Models
used
The correspondence with Professor Neil Ferguson
is shown HERE.
Unfortunately we are as yet none the wiser about
the basis for the model that Neil Ferguson and his colleagues have
used to predict what would happen under various scenarios whereby
the OTM rule was relaxed. It looks as though the information is
tied up in papers that have been submitted for publication.
Let us hope, therefore, that once the journal/s
involved in the peer-review have decided about publication that
this can be done on-line without further delay. There is little
point in the FSA making a public announcement and holding a public
meeting if the evidence on which an essential part of what is proposed
is not available for public assessment. People are now much more
wary about the predictions by modellers than they used to be. They
will want to know what assumptions have been made, and whether or
not they are credible.
Further information on the testing for BSE
in cattle before they enter the food chain
The correspondence with Professor John Wilesmith
is shown HERE.
His response is very helpful and much appreciated.
The references to which he refers are given below (2,
3). A further relevant reference is also given
(4).
Professor Wilesmith confirms that the currently
used tests that have the approval of the EC are all of the post-mortem
variety. Antemortem tests, such as recently published online by
Professor Ebringer et al (5),
have still to be evaluated.
According to Professor Wilesmith the postmortem
tests can be carried out overnight, and that contamination between
carcases (in the event of a positive test being recorded next morning)
can be dealt with by discarding from the food chain the carcase
in line before the one with a positive test and the next two. Somehow
I think we should know more about the logistics of all this when
it is operating in practice in a large (or indeed small) abattoir.
Where are these laboratories in relation to the abattoirs? How many
days can a carcase be there, waiting for the laboratory results:
and are the results of the tests really back from the lab the next
day (or do they need to be)? Are the precautions to prevent cross-contamination
in the abattoir sufficient?
When assessing the practical application of a
test, it would be standard practice in the field of clinical medicine
to do the assessment in two stages. The first stage would be to
do what is described in ref 3, whereby known positive
and negative samples were sent to participating laboratories. The
second stage would be to see how the tests actually work out in
routine practice. What seems to me to be lacking is any documented
evidence of the latter. Many tests behave well under test conditions,
but fail to live up to expectations when all the hassles, inconveniences
and slip-ups of routine practice come into play.
Professor Wilesmith makes it quite clear that
there is no satisfactory information about how accurately any of
the three currently recommended Kit tests (BioRad (CEA), Enfer and
Prionics) for the post-mortem detection of BSE in cattle could pick
up early disease. Could early stage BSE pose a danger to man should
the meat enter the food chain?
References
1. Irvine, James
(2003). The Food Standards Agency reviews the OTMS rule - are they
going to scrap it?
(Filed 12 March 2003, www.land-care.org.uk,
click here to view).
2. Moynagh J.
& Schimmel, H. (1999). Tests for BSE evaluated. Nature, 400:
105. (Download
PDF). Reproduced with permission.
3. European
Commission (1999). Preliminary Report: The Evaluation of tests for
the diagnosis of transmissible spongiform encephalopathy in bovines.
8 July 1999. (Download
PDF).
4. Butler, D.
(1998). Brussels seeks BSE diagnostic test to screen European cattle.
Nature, 395: 205. (Download
PDF). Reproduced with permission.
5. Wilson, C.,
Hughes, L. E., Rashid, T., Ebringer, A. and Bansal, S. (2003).
Antibodies to Acinetobacter Bacteria and Bovine Brain Peptides,
Measured in Bovine Spongiform Encephalopathy (BSE) in an Attempt
to Develop an Ante-Mortem Test.
J. Clin. Lab. Immunol. Published online, 13 March 2003. (Download
PDF).
Further Reading Recommended by Land-Care
Irvine, James (2003). Current Assessment of the Future Prevalence
of vCJD in the UK.
(Filed 12 March 2003, www.land-care.org.uk,
click here
to view).
Detection of Prions: Developing Technology
(Filed 12 March 2003, www.land-care.org.uk,
click
here to view).
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