WORLD TRADE
ORGANIZATIONG/SPS/GEN/221
5 December 2000
(00-5249)
Committee on Sanitary and Phytosanitary Measures Original:  English
BOVINE SPONGIFORM ENCEPHALOPATHY (BSE)
Submission by the World Health Organization (WHO)1
1. Bovine Spongiform Encephalopathy (BSE) is a fatal, neuro-degenerative, transmissible brain
disease of cattle.  The disease is fatal for cattle within weeks to months of its onset.  BSE first came to
the attention of the scientific community in November 1986 with the appearance in cattle of a newly-
recognized form of neurological disease in the United Kingdom.
Source of the epidemic2. Epidemiological studies conducted in the United Kingdom suggest that the source of BSE
was cattle feed prepared from carcasses of ruminants, and that changes in the process of preparing
cattle feed may have been a contributing risk factor.
3. Speculation as to the cause of the appearance of the agent causing the disease has ranged from
spontaneous occurrence in cattle, the carcasses of which then entered the cattle food chain, to entryinto the cattle food chain from the carcasses of sheep with a similar disease, scrapie.
Cause
4. BSE is associated with a transmissible agent.  The agent affects the brain and spinal cord of
cattle and lesions are characterized by sponge-like changes visible with an ordinary microscope.
5. The agent is highly stable, resisting freezing, drying and heating at normal cooking
temperatures, such as those used for pasteurization and sterilization at usual temperatures and forusual times.
6. Under investigation, the nature of the BSE agent is still a matter of debate.  According to the
prion theory, the agent is composed largely, if not entirely, of a self-replicating protein, referred to as
a prion.  Another theory argues that the agent is virus-like and possesses nucleic acids which carry
genetic information.  Although strong evidence collected over the past decade supports the priontheory, the ability of the BSE agent to form multiple strains is more easily explained by a virus-like
agent.
Cases of BSE
7. Between November 1986 and November 2000 ap proximately 180,000 cases of this newly
recognized cattle disease were confirmed in the United Kingdom.
8. Since 1989 when the first BSE case was reported outside of the United Kingdom, relatively
small numbers of BSE cases (in total approximately 1,500) have also been reported in native cattle in
                                                     
1 Fact Sheet N° 113, revised November 2000.G/SPS/GEN/221
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Belgium, Denmark, France, the Republic of Ir eland, Liechtenstein, Luxembourg, Netherlands,
Portugal and Switzerland.  However, all but a couple of dozen have been reported in four countries –
Ireland, Portugal, Switzerland and France.  Small numbers of cases have also been reported in
Canada, the Falkland Islands (Islas Malvinas), Germany, Italy and Oman, but solely in animals
imported from the United Kingdom.  The International Office for Epizootic Diseases (OIE) reportsthese cases on their web site: www.OIE.int
Measures taken to prevent the spread of BSE
9. In July 1988, the United Kingdom banned the use of ruminant proteins in the preparation of
animal feed.  The use in the food chain of bovine offals considered to pose a potential risk to humans
was also banned in the United Kingdom in 1989, and the list was revised and expanded on several
occasions as new information became available.  In other countries, including European countries,measures taken, the date of implementation and the extent of enforcement vary from country to
country.
10. Starting in 1996, bans prevented the sale of f ood and food products containing beef from the
United Kingdom to other countries.  Other products (e.g. tallow, gelatin) derived from bovine tissues
were also prohibited from sale from the United Kingdom to other countries.  However, the EuropeanUnion recently lifted the ban for meat fulfilling specific requirements; for example, de-boned beef
from animals from farms where there have been no cases of BSE and where the animals are less than
30 months of age at slaughter.
11. Cattle are continuously monitored for BSE and BSE is decreasing in the United Kingdom.
New monitoring programmes using newly developed tests for the diagnosis of BSE in dead cattlehave been introduced in Switzerland and France, and may be expected throughout the European
Union.
Transmissible Spongiform Encephalopathies (TSEs) in animals
12. TSEs are diseases characterized by spongy degeneration of the brain with severe and fatal
neurological signs and symptoms.  BSE is one of several different forms of transmissible brain
disease affecting a number of animal species.  Scrapie is a common disease in sheep and goats.  Mink,
as well North American mule deer and elk, can contract TSEs.  A neurological disease in household
cats and in ruminant and feline species in zoos has been linked to consumption of food contaminated
by BSE; most cases in such animals appear to have occurred in the United Kingdom.
Creutzfeldt-Jakob disease13. While several human TSEs exist, Creutzfeldt-Jakob disease (CJD) is the prototype human
TSE.  CJD occurs in a form associated with a hereditary predisposition (approximately 5-10 per cent
of all cases) and in a more common, sporadic form that accounts for 85-90 per cent of cases.
14. A small percentage of cases (less than 5 per cent) are iatrogenic (resulting from the accidental
transmission of the causative agent via contaminated surgical equipment or as a result of cornea ordura mater transplants).  It has also been shown that CJD can be transmitted to humans as a result of
treatment with natural human growth hormone.  Such means of transmission have now been
controlled in the industrialized countries where these procedures were practised.
15. A newly recognized form of CJD, variant Creutzfeldt-Jakob disease (vCJD) was first reported
in March 1996 in the United Kingdom (cf. WHO Fact Sheet N° 180 on variant Creutzfeldt-JakobDisease).  In contrast to classical forms of CJD, vCJD seems to affect mainly young patients and has a
relatively long duration of illness.  In contrast to the traditional forms of CJD, vCJD has affectedG/SPS/GEN/221
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younger patients (average age 29 years, as opposed to 65 years), has a relatively longer duration of
illness (median of 14 months as opposed to 4.5 months) and is strongly linked to exposure, probably
through food, to a TSE of cattle called Bovine Spongiform Encephalopathy (BSE).
16. From October 1996 to early November 2000, 85 cases of vCJD have been reported in the
United Kingdom, three in France and a single case in the Republic of Ireland.  Insufficientinformation is available at present to make any well-founded prediction about the future number of
vCJD cases.
17. Since few countries have surveillance systems, the geographical distribution of the incidence
of vCJD needs to be better defined.
18. Recent studies have confirmed that vCJD is due to a strain of agent which is distinct from that
of sporadic and acquired CJD.  Similarities observed between the strain of the agent responsible for
vCJD and those of BSE and closely related agents transmitted naturally and experimentally todifferent animal species, are consistent with  the hypothesis discussed during two 1996 WHO
consultations: that the cluster of vCJD cases is due to the same agent that caused BSE in cattle.  The
route of exposure is unknown, but seems likely to be through food.
19. Further data are urgently required from scientific studies on vCJD cases.  More retrospective
and prospective monitoring and surveillance studies on all forms of CJD, modelled on currentEuropean collaborative studies, are required throughout the world.
World Health Organization (WHO) work on TSEs
20. Since 1991, WHO convened nine scientific consultations on issues related to human and
animal TSEs; the ultimate goal of the meetings was to better protect human and animal health.Experts who participated reviewed the possible human public health implications of animal TSEs,
with special emphasis on BSE.  The consultations al so reviewed the evolving state of knowledge on
these diseases, evaluated possible means of transmission and identified risk factors for infection.
21. The group of independent experts assembled by WHO is continually updating the state-of-
the-art as more scientific information on BSE and vCJD becomes available.  WHO provides a neutralscientific forum in which scientific questions related to BSE and vCJD can be reviewed, evaluated
and debated.
22. Advancing current knowledge about TSEs through research will permit the best possible
decisions to be taken to safeguard public health, while securing consumer confidence so that national
economies dependent on the beef industry can be maintained and developed.  Therefore, research on
all TSEs is promoted by WHO, especially on early diagnostic procedures and epidemiology.  WHO
has published a comprehensive priority list for new research.  One question which needs investigationis whether or not BSE has infected sheep populations.
23. WHO is helping to expand standardized surveillance of CJD and its variants in order to better
understand the disease's geographic spread in the world and to better protect public health globally.
From 1997-2000, WHO held a series of training c ourses worldwide, particularly in developing
countries, with the intention of helping individual countries establish national surveillance of CJD andits variants.
24. WHO published guidelines for infection control of TSEs in 2000.  The full text is available at
http://www.who.int/emc-documents/  under the heading "TSE".G/SPS/GEN/221
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WHO conclusions and recommendations to reduce exposure to the BSE agent
25. Recent studies have confirmed that vCJD is due to a strain of agent which is distinct from that
of sporadic and acquired CJD.  Similarities observed between the strain of the agent responsible for
vCJD and those of BSE and closely related agents transmitted naturally and experimentally todifferent animal species, are consistent with  the hypothesis discussed during two 1996 WHO
consultations, that the cluster of vCJD cases is due to the same agent that caused BSE in cattle.  The
route of exposure is unknown, but seems likely to be through food.
26. BSE must be eradicated.  All countries must pr ohibit the use of ruminant tissues in ruminant
feed and must exclude tissues that are likely to contain the BSE agent from any animal or human food
chain.  All countries are encouraged to conduct risk assessments to determine if they are at risk for
BSE in sheep and goats.  It is advised that any tissue which may come from deer or elk with Chronic
Wasting Disease (CWD is a transmissible spongiform disease of mule deer and elk) is not used in
animal or human food; however, at this time there is no evidence to suggest that CWD in deer and elk
can be transmitted to humans.
27. Human and veterinary vaccines prepared from bovine materials may carry the risk of
transmission of animal TSE agents.  The pharmaceutical industry should ideally avoid the use ofbovine materials and materials from other animal species in which TSEs naturally occur.  If
absolutely necessary, bovine materials should be obtained from countries which have a surveillance
system for BSE in place and which report either zero or only sporadic cases of BSE.  These
precautions apply to the manufacture of cosmetics as well.
28. Milk and milk products are considered safe.  Tallow and gelatin are considered safe if
prepared by a manufacturing process which has been shown experimentally to inactivate the
transmissible agent.  No infectivity has yet been detected in skeletal muscle tissue.  Reassurance can
be provided by removal of visible nervous and lymphatic tissue from meat (skeletal muscle).
Note:  For further information, journalists can contact the Spokesperson’s Office, WHO, Geneva
Telephone (+41 22) 791 2599. Fax (+41 22) 791 4858. E-mail: inf@who.int .  All WHO Press
Releases, Fact Sheets and Features can be obtained on Internet on the WHO home page: www.who.int .
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