NR ASFP
AU anonym
AK WHO - World Health Organization
TI Fact Sheet 113 (revised) April 1996 - BOVINE SPONGIFORM ENCEPHALOPATHY (BSE)
QU Internet
IA http://www.who.ch/programmes/inf/facts/fact113.htm
PT WHO - Fact Sheet
VT
Bovine Spongiform Encephalopathy (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. Between November 1986 and May 1995 approximately 150 000 cases of this newly-recognized cattle disease were confirmed from approximately 33 500 herds of cattle in the UK. Epidemiological studies in the United Kingdom at that time suggested that the source of disease was cattle feed prepared from carcasses of dead ruminants, and that changes in the process of preparing cattle feed introduced in 1981-1982 may have been a risk factor. Speculation as to the cause of the appearance of the disease in the food chain of cattle has ranged from spontaneous occurrence in cattle, the carcasses of which then entered the cattle food chain; to entry into the cattle food chain from the carcasses of sheep with a similar disease.
BSE is associated with a transmissible agent, the nature of which is not yet fully understood. The agent affects the brain and spinal cord of cattle and lesions are characterized by sponge-like changes visible with an ordinary microscope. It is a highly stable agent, resisting heating at normal cooking temperatures and to even higher temperatures such as those used for pasteurization, sterilization at usual temperatures and times, as well as to freezing and drying. The disease is fatal for cattle within weeks to months of its onset.
By May 1995, BSE had been reported from 10 countries and areas outside the United Kingdom. In one group of countries - France, Portugal, Republic of Ireland and Switzerland - the disease occurred in native cattle, and this was thought to be in part related to importation of cattle feed from the UK. In another group - Falkland Islands (Las Malvinas), Oman Sultanate, Germany, Canada, Italy and Denmark - cases were only identified in cattle imported from the UK.
In July 1988 the UK banned the use of ruminant proteins in the preparation of cattle feed, and in November 1989 the UK banned the use of brain and spinal cord - as well as tonsil, thymus, spleen and intestine - of cattle origin (known as Specified Bovine Offals or SBOs) in foods for human consumption. Cattle are continuously monitored for BSE in all affected countries, and BSE is decreasing in the UK.
BSE is one of several different forms of transmissible brain disease of animals. Others include scrapie, a disease common in sheep; a similar neurological disease in animals such as the mink, and in North America in mule deer and elk; and, recently, neurological disease in household cats, and in captive bovine and feline species, the majority of which appear to have been in the United Kingdom.
Diseases in humans with sponge-like findings in brain under the microscope, and with severe and fatal neurological signs and symptoms, include kuru, a disease which appears to be transmitted by human ritual handling of bodies and brains of the dead; and Creutzfeldt-Jakob disease (CJD). CJD occurs in a form associated with a hereditary predisposition (approximately 10% of cases); and in a more common, sporadic form that accounts for the remaining 90%. In recent years, it has been shown that CJD can be transmitted to humans by treatment with natural human growth hormone or grafting of tissues surrounding human brain, and these means of transmission have now been controlled in the industrialized countries where these procedures were practised. Another similar human disease is Gerstmann-Sträussler-Schenker (G.S.S.) syndrome which appears to be familial, occurring in persons with an apparent hereditary predisposition.
After the identification of BSE, and as a regular activity to continue the study of the possible hazards of BSE for humans, WHO held three meetings on the spongiform encephalopathies in 1991, 1993 and 1995; and one in collaboration with the Office of International Epizootics in 1994. The purpose of these meetings was to review the existing state of knowledge on spongiform encephalopathies including BSE, to evaluate possible means of transmission, and to identify risk factors for infection. An express purpose of these meetings was to review the possible human public health implications of animal spongiform encephalopathies, with special emphasis on BSE.
The most recent WHO meeting compared the annual number of cases of CJD in France, Germany, Italy, Netherlands and the United Kingdom. This comparison showed that rates were similar in all these countries (approximately 1 per million), as was the age distribution and duration of illness prior to death, and conclusions of this meeting were that the epidemiological evidence in Europe did not indicate a change in the incidence of CJD that could be attributed to BSE. Cases reported from the United Kingdom were those which were identified through routine reporting and from an intensified surveillance system for CJD-like illness which had been set up in 1990.
A newly recognised variant form of CJD was identified in 10 patients in the UK during the 12 month period after this most recent WHO meeting and was first reported by the United Kingdom in March 1996. In contrast to typical cases of sporadic CJD, this variant form affected young patients (mean age 26.3 years) with a relatively long duration of illness (mean 14.1 months).
The characteristic neuropathological profile in this variant consists of numerous widespread Kuru-type amyloid plaques with surrounding vacuolation and severe cerebellar lesions. No abnormalities in the prion protein gene have been demonstrated so far in any of the cases.
Case definition for V-CJD. To date, so far all patients identified in the UK who have died were 41 years of age or less.
A suspect case shows the following clinical features:
A psychiatric presentation with anxiety, depression, withdrawal and other behavioural changes with progression to neurological abnormalities.
Onset of a progressive cerebellar syndrome within weeks or months of presentation.
Forgetfulness and other memory impairment, with dementia in the late stages.
Myoclonus in the late stages.
The EEG does not show the changes normally observed in classical CJD. Less common features include early onset of dyasesthesia in limbs and face at presentation, and chorea, extrapyramidal and pyramidal signs later in the illness. Neuropathological diagnosis is mandatory for confirmation of suspected V-CJD cases. Confirmatory examination of the brain should show the following neuropathological features:
Numerous widespread Kuru-type amyloid plaques surrounded by vacuoles.
Spongiform change most evident in the basal ganglia and thalamus.
Prion protein accumulation in high density shown by immunocyto-chemistry, particularly in the cerebellum.
At present there have been 10 cases of V-CJD reported in the UK and one case reported in France; its geographical distribution, however, needs to be better defined.
A link has not been proven between V-CJD and the effect of exposure to the BSE agent, although this is the most likely hypothesis. Further data are urgently required from scientific studies on these variant cases. More retrospective and prospective monitoring and surveillance studies on all forms of CJD, modelled on current European collaborative studies, are required throughout the world.
At a consultation organized by WHO on 2-3 April 1996, the following recommendations for the protection of public health were made:
1. No part or product of any animal which has shown signs of a TSE should enter any food chain (human or animal). In particular:
All countries must ensure the killing and safe disposal of all parts or products of such animals so that TSE infectivity can not enter any food chain.
All countries should review their rendering procedures to ensure that they effectively inactivate TSE agents.
2. All countries should establish continuous surveillance and compulsory notification for BSE according to the recommendations of the International Animal Health Code of the Office International des Epizooties (OIE).
In the absence of surveillance data the status of a country with respect to the occurrence of BSE must be considered as unknown.
3. Countries should not permit tissues that are likely to contain the BSE agent to enter any food chain (human or animal).
4. All countries should ban the use of ruminant tissues in ruminant feed.
5. With respect to specific products:
Milk and milk products, even in countries with a high incidence of BSE, are considered safe. There is evidence from other animal and human spongiform encephalopathies to suggest that milk does not transmit these diseases.
Gelatin in the food chain is considered to be safe if produced by a manufacturing process utilizing production conditions which has been demonstrated to significantly inactivate any residual infectivity that may have been present in source tissues. Tallow is likewise considered safe if effective rendering procedures are in place .
6. The risk, if any, of exposure to the BSE agent in countries other than UK is considered lower than in UK. Exposure to the BSE agent in UK was likely to be higher prior to the current BSE regulations. More studies are required to allow a full risk assessment. Incomplete risk assessment hinders accurate risk communication and perception.
The risks at present associated with exposure to the BSE agent from beef and beef products will be minimized if the recommendations of the present group are implemented.
7. Risks from medicinal products and medical devices containing bovine tissues:
The importance of obtaining bovine materials destined for the pharmaceutical industry only from countries which have a surveillance system in place and which report either no or only sporadic cases of BSE is reiterated.
Removal and inactivation procedures contribute to the reduction of the risk of infection but it must be recognized that the BSE agent is remarkably resistant to physico-chemical procedures which destroy the infectivity of common microorganisms.
Measures recommended to national health authorities to minimize the risk of transmitting the agent causing bovine spongiform encephalopathy via medicinal products, in particular parenteral products, which were developed at the WHO Consultation in 1991 (Bulletin of the World Health Organization, 1992; 70, 183-190) continue to be generally applicable.
It is recommended that these measures be reviewed and, if necessary, strengthened, as more information becomes available.
8. Research on TSE should be promoted especially as regards rapid diagnosis, agent characterisation, and epidemiology of TSEs in humans and animals.
For further information, please contact Health Communications and Public Relations, WHO, Geneva, Telephone (41 22) 791 2535. Fax (41 22) 791 4858.
All WHO Press Releases, Fact Sheets and Features can be obtained on Internet on the WHO home page http: //www.who.ch/
IN
Eine von der WHO am 2. und 3. April 1996 organisierte Versammlung angeblicher BSE-Experten sprach folgende Empfehlungen aus:
1. Von Tieren mit Anzeichen für eine übertragbare schwammförmige Gehirnschädigung darf in die Nahrungsketten von Menschen oder Tieren gelangen. Sie sollen getötet und sicher entsorgt werden. Alle Länder sollen die Effektivität ihrer Tierkörperbeseitigungsanlagen bezüglich der Inaktivierung der Überträger schwammförmiger Gehirnschädigungen überprüfen.
2. Alle Länder sollen den Normen des Office International des Epizooties (OIE) BSE-Überwachungssysteme einrichten. Solange dies nicht geschehen ist, muß ihr BSE-Status als ungeklärt gelten.
3. Gewebe, die BSE-Erreger enthalten könntn, sollen in keine Nahrungskette gelangen.
4. Die Verwendung von Wiederkäuergewebe in Wiederkäuerfutter sollte in allen Ländern verboten werden.
5. Milch und Milchprodukte werden von den WHO-Experten selbst dann für sicher gehalten, wenn sie aus England stammen. Sie behaupten, es gebe Hinweise von tierischen und menshlichen spongiformen Enzephalopathien, die gegen eine Übertragbarkeit durch Milch sprächen. Das es einen gegenteiligen Beweis gibt, erwähnen sie nicht. Gelatine in der Nahrungskette wird für sicher erklärt, sofern sie mit einer Methode produziert wird, welche nachweislich alle Errger inaktiviert. Analog wird auch die Sicherheit von Talg bescheinigt, sofern er durch eine effektive Tierkörperverwertungsprozedur produziert wird.
6. Das BSE-Risiko ist außerhalb von England größer als in England, falls es überhaupt besteht. Zudem halten die WHO-Experten eine Verminderung des BSE-Risikos durch die aktuellen BSE-Schutzmaßnahmen für wahrscheinlich. Für eine noch bessere Risikoanalyse benötigen sie mehr Studien. Was für eine Erleuchtung!
7. Die pharmazeutische Industrie soll Rinderprodukte nur aus erwiesenermaßen praktisch BSE-freien Ländern beziehen, da der Erreger extrem resistent ist. Die Schutzregelungensollen verschärft werden, wenn neue Erkenntnisse dies nahelegen. Dies ist gerade keine vorbeugende Gesundheitspolitik.
8. Natürlich verlangen die Superexperten mehr Forschungsmittel.
AD Health Communications and Public Relations, WHO, Geneva, Telephone (41 22) 791 2535. Fax (41 22) 791 4858.
PO Internet
SP englisch