Transmissible Spongiform Encephalopathies in sheep and goats
- answers from the European Commission
The European Commission has issued a series of answers to
a selection of questions on Transmissible Spongiform Encephalopathies (TSE),
the family of illnesses that includes Creutzfeldt Jakob Disease (CJD) in
humans, Bovine Spongiform Encephalopathy (BSE) in cattle, and scrapie in
sheep and goats (http://europa.eu.int/rapid/start/cgi/guesten.ksh?p_action.gettxt=gt&doc=MEMO/03/157|0|RAPID&lg=EN&display
The document states that scrapie is not considered to be transmissible to
humans or to pose a risk to man on the basis of the available data. European
Union (EU) legislation to prevent the spread and transmission of BSE, however,
does apply also to sheep and goats as a precautionary measure (for example,
removal of specific risk material like brain and spinal cord since 2000,
ban of feeding mammalian meat and bone meal (MBM) to ruminants since 1994).
The principal transmission route of BSE is thought to be MBM derived from
material from infected animals. BSE has never been found in sheep living
in fields. During the 1980s and early 1990s sheep in the United Kingdom
and elsewhere were partially fed with feedstuffs containing the same type
of contaminated MBM that was responsible for causing the spread of BSE in
cattle. This has caused scientists to question whether BSE might also have
infected the population of small ruminants. The feeding of MBM to ruminants
has been forbidden in the EU since 1994 (1) and a total ban on feeding MBM
to farmed animals has been in place since January 2001 (2).
It has also been known for some time that a BSE-like disease can be experimentally
transmitted to sheep by feeding them material derived from the brains of
BSE-affected cows. This artificially produced disease in research trials
cannot be distinguished from scrapie by examination of clinical symptoms
or by rapid tests on the brains. It can only be distinguished with certainty
from scrapie by the use of a mouse bioassay, a testing technique that may
take up to two years to complete. The limited number of mouse bioassays
that have been done on natural scrapie cases so far have failed to yield
a BSE-like strain, and to date there is no evidence of the existence of
BSE in the sheep and goat population under natural conditions. New evidence
is constantly being reviewed by the EU scientific committees.
The most recent opinions of the Scientific Steering Committee
(SSC) on BSE in small ruminants were adopted in April 2002 (http://europa.eu.int/comm/food/fs/sc/ssc/out257_en.pdf
updating previous opinions of October 2001 (http://europa.eu.int/comm/food/fs/sc/ssc/out234_en.pdf),
February 2001 (http://europa.eu.int/comm/food/fs/sc/ssc/out170_en.pdf),
and September 1998 (http://europa.eu.int/comm/food/fs/sc/ssc/out24_en.html).
The opinion reaffirms the SSC's view that there is no evidence that BSE
is present in small ruminants under field conditions. It issues a range
of recommendations in terms of specified risk material, use of rapid tests,
individual identification, breeding for resistance, flock certification,
and culling measures. It also describes how a combination of approaches
might be used to protect public health in the event of BSE being confirmed
in small ruminants under field conditions.
More information on TSE and BSE is available from the Food Safety section
of the European Commission website (http://europa.eu.int/comm/food/fs/bse/index_en.html).