Supplementary memorandum submitted by
Professor David King, Chief Scientific Adviser, Office of Science
and Technology
Thank you for your letter of 7 November, in
which you asked me to provide further material relating to the
answers I gave at the evidence session earlier that day. I apologise
for the delay in replying. This was caused by having to obtain
further information from various sources.
First; on testing for BSE in sheep. Between
November 2000 and the end of September 2001, 465 sheep scrapie
suspects have been tested at the Veterinary Laboratories Agency
using a molecular testing method based on a modified version of
a Western blot test used to detect BSE in cattle. 284 were found
to be positive for scrapie; none have given results that suggest
BSE. However, this test remains unvalidated for distinguishing
between BSE and scrapie.
Scrapie-infected sheep brains, collected since
1996, are also being strain-typed at the Institute for Animal
Health, using mouse bio-assay. In about 180 cases this work has
reached the first point at which, if BSE were clearly present,
it should have become apparent. It has not done so, but the work
is still ongoing and these experiments cannot yet be interpreted
as being definitively negative for BSE.
The second query was about the current incidence
of BSE in cattle. The BSE epidemic peaked in the UK during the
winter of 1992-93, when over 1,000 suspected cases were being
reported each week. In the current year, clinical BSE cases are
likely to be around 750 and the epidemic appears to be declining
broadly in line with epidemiological predictions. Active surveillance
checks have been, or are being, carried out by MAFF/DEFRA to find
levels of sub-clinical disease in cattle. These are:
— Surveys of animals aged 5 years and
over, presented for slaughter under the Over Thirty Months Slaughter
Scheme from January to March 1999 and from May to December 2000.
— Since 1 January 2001, any animals
aged over 30 months and slaughtered for human consumption must
be tested for BSE before the carcass is released. In the UK, this
relates to a small number of animals from herds belonging to the
Beef Assurance Scheme.
— A voluntary survey of fallen stock
aged 30 months and notified to the department from January to
July 2001, superseded by a compulsory survey that began on 1 July
2001.
— A survey of animals aged 30 months
or over and subject to emergency slaughter (casualty animals)
also began on 1 July 2001.
— Cattle born between 1 August 1996
and 31 July (the year after the effective feed ban) as they enter
the Over Thirty Month Scheme. This testing began in September
2001.
— Testing the offspring of BSE cases
aged over 30 months from 10 September 2001.
— From January 2002, 24-30 months fallen
stock and casualty cattle will be tested.
This testing has found pre-clinical cases of
BSE, but not at a level so far to indicate that the disease exists
widely in an undetected state.
The Committee's third request was for my comments
on a written answer given by Elliot Morley (HC Deb, 6 November
2001, 146W) relating to the number of premises culled out as Dangerous
Contacts and Slaughter on Suspicion cases which were found subsequently
to have Foot and Mouth Disease. I understand that DEFRA will shortly
be issuing a corrected answer and that the relevant figures are:
284 premises currently classified as Slaughter on Suspicion and
396 premises currently classified as Dangerous Contact had laboratory
tests conducted for the presence of Foot and Mouth Disease. Of
these, one returned an initial positive result.
The fact that all but one of the premises have
tested negative does not mean that the policy of culling out Dangerous
Contacts and Slaughter on Suspicion cases is too stringent. FMD
is an extremely infectious disease and, in order to bring the
epidemic under control, it was necessary to get ahead of the infection
by removing animals that were potentially already incubating the
virus and, if not slaughtered, would themselves pass the infection
on. Currently available diagnostic tests are not fast or sensitive
enough to spot incubating infection quickly enough to prevent
it becoming a risk to surrounding farms.
13 December 2001
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