Brussels, 21 September 2000
EU scientists advise on BSE-related culling and review recent BSE research
The Scientific Steering Committee has today published an opinion on BSE-related culling, statements on recent publications on BSE related research as well as a positive opinion on the safety of bone-in-veal exports from the UK. After having evaluated recent studies about the possible endemic presence at very low levels of BSE in scrapie carrying sheep, and the possibility of BSE in other animals such as pigs, poultry and fish, the Committee does not see any cause for alarm, immediate action or a revision of its standing opinions. Its standing advice and recommendations on the risk of BSE type infections in sheep and other animals already take sufficient account of such possibilities insofar as they have been substantiated by currently available evidence or anticipated by the experts advising the Committee. The Committee will however continue to closely monitor any new evidence that may become available. The Committee considers that the conclusions of a recently published communication predicting significantly lower numbers of vCJD cases than previously assumed are premature.
BSE related Culling
The SSC adopted an opinion on culling strategies for herds with confirmed BSE cases. In most countries it is currently standing practice to slaughter the entire herd to which a confirmed BSE case belongs or was born in to prevent further propagation of the disease, as is the routine with other infectious animal diseases that are transmitted from animal to animal. These specific characteristics of BSE suggest that slaughtering entire herds is not necessarily a more effective strategy to root out a BSE epidemic than a more focused approach targeting all cattle fed from the same feed as a confirmed case ("feed-cohorts"). Birth-cohorts, including all animals born or raised in the same herd within a specified period before or after the birth of a confirmed BSE case, are found to be in most cases a more effective approximation to the ideal "feed-cohort" than the current and natal herd. The available data indicate that birth-cohorts cover most, if not all, additional cases that were found in herd culling exercises so far, the Committee states. Therefore a birth-cohort culling strategy would have very much the same beneficial effect as a herd-culling strategy while reducing the number of animals culled by two thirds.
Bone-in-veal exports from the UK
The Committee concluded that bone-in-veal exports from the UK within the framework of the DataBasedExport 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 its risk assessment. The SSC considers that the cow concerned was in any case 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 did however call for careful tracing and detailed study of such exceptional cases to precisely determine the origin of the infection. If evidence of a feed-borne origin were to be found, this would require a review of its risk assessment.
Presence of BSE prion in sheep
The Committee concluded that Prof. Prusiner's hypothesis that low levels of BSE prions could possibly be endemic in sheep carrying scrapie does not at this point provide grounds to review its standing advice concerning the need for measures to reduce the risk of Transmissable Spongiform Encephalopathies (TSE's) in sheep and goats. The Committee also said it intends to carefully monitor the further results of Prof. Prusiner and others in the context of its ongoing work to proactively assess the eventual risks if BSE in sheep would be confirmed under natural conditions. Prof. Prusiner's hypothesis was made public through media reports in July, but the research on which it is based has not yet been finalised or published.
Presence of TSE infectivity in poultry, fish and pigs
The Committee also reviewed a paper co-authored by Prof. Collinge on the possible presence of subclinical TSE infectivity in certain animals and its implications for the transmission of TSE's between different animal species. The Committee concludes that most of the scientific evidence on which this thesis is based has already been taken into account or anticipated in its standing opinions. The Committee has always based its advice on a very low barrier for transmission of BSE from one type of animal to another. It has therefore recommended measures such as removal of specified risk materials, safe geographical sourcing, appropriate production processes and exclusion of dead animals and fallen stock from the feed chain to avoid intra-species recycling. In the light of the Collinge paper the Committee is requesting the most up-to-date results of ongoing UK and European research into the presence of BSE type infections in pigs, poultry and fish.
Prediction of vCJD-cases
The Committee also reacted to a report published in 'Nature' in August by a UK research team directed by Prof. Anderson predicting significantly lower numbers of cases variant Creutzfeldt-Jacob Disease (vCJD) than assumed so far. The scientists found that the team's assumption that one infected cow would on average cause no more than two cases of vCJD is not supported by the published data and in itself questionable. Making such predictions remains very difficult given the many unknowns at this stage . It therefore stands by its relevant opinion on human exposure to the BSE agent of April this year.
The full text of the opinion on the safety of veal exports from UK and an extract of the minutes of the SSC meeting of 14-15 September containing the statements on new BSE research developments are available at http://ec.europa.eu/food/fs/sc/ssc/outcome_en.html
Released on 25/09/2000