Brussels, 22/09/2000 (Agence Europe) - Asked to state its views on strategies for the slaughtering of herds contaminated with bovine spongiform encephalopathy (BSE), exports of bone-in veal from the UK and recent scientific publications concerning the possibility of the BSE agent of infection crossing species barriers, the EU's Scientific Steering Committee has issued the following opinions.
1. Slaughtering of herds. To eradicate an epidemic of BSE, the slaughtering of entire herds is not necessarily more effective than a selective approach targeting all cattle fed from the same feed ("feed cohorts").
According to the Committee, available findings reveal that birth cohorts (i.e. all the animals born or raised in the same herd within a specified period before or after the birth of a confirmed case of BSE) cover most if not all additional cases found in herd culling exercises so far. Consequently, a birth cohort culling strategy would have very much the same beneficial effects as a herd culling strategy, while reducing the number of animals slaughtered by two thirds.
2. Exports of bone-in veal from the United Kingdom. Exports within the framework of the data based export scheme (DBES) are to be considered safe. The discovery of a case of BSE in a cow born after 1 August 1996 did not influence the Committee's risk assessment. Indeed, the Steering Committee considers that the animal in question was not eligible under the DBES and that exceptional cases were to be expected as a result of transmission of BSE from cow to calf. The Committee nevertheless called for careful tracing and detailed study of such exceptional cases to determine precisely the origin of the infection. If evidence of a feed-borne origin were to be found, a review of risk assessment would be required.
3. Presence of BSE prion in sheep. Professor Prusiner's hypothesis that low levels of BSE prions could possibly be endemic in sheep carrying scrapie does not at this point justify a review of the Committee's opinion concerning the need for measures to reduce the risk of Transmissible Spongiform Encephalopathies (TSEs) in sheep and goats. The Committee intends to monitor carefully the findings of Professor Prusiner's research (which have been reported by the press but not yet finalised or published) to assess eventual risks, if BSE in sheep should be confirmed under natural conditions.
4. Presence of TSE infectivity in poultry, fish and pigs. After a review of the paper by Professor Collinge on the possible presence of subclinical TSE infectivity in certain animals other than bovine species, and its implications for the transmission of TSEs between different animal species, the SSC concluded that most of the scientific evidence on which this thesis is based has already been taken into account or anticipated in its standing opinions based on the hypothesis of a low barrier for transmission of BSE from one type of animal to another. The measures it recommended (elimination of specified risk material from the animal and human food chain, safe geographical sourcing, appropriate production processes and exclusion of dead animals and fallen stock from the feed chain to avoid intra-species recycling) were based on this hypothesis.
5. Prediction of cases of the human variant of mad cow disease. Reacting to the article published in August in the magazine "Nature" on the findings of research by a British team led by Professor Anderson predicting a lower number of cases of the new variant of Creutzfeldt-Jacob disease (vCJD), the SSC considers that: a) it remains very difficult to make such predictions given the many unknowns at this stage; b) the assumption that one infected cow would on average cause no more than two cases of vCJD is not supported by published data and is in itself questionable.
The Scientific Steering Committee therefore stands by its relevant opinion of April this year on human exposure to the BSE agent.
The full text of the opinion on bone-in veal exports from the United Kingdom and statements on the latest developments in BSE research are available at http: //europa.eu.int/comm/food/fs/sc/ssc/outcome.