Annual report : 1997-1998 / Spongiform Encephalopathy Advisory Committee.

  • Great Britain. Spongiform Encephalopathy Advisory Committee
Date:
1998
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Credit: Annual report : 1997-1998 / Spongiform Encephalopathy Advisory Committee. Source: Wellcome Collection.

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    date of BSE onset in the dam. For calves born before onset, the risk was lower, and diminished as the interval between birth and onset increased, and no risk was apparent more than two years before onset (see next paragraph). Thus, although possibly subject to some biases, these analyses also suggested that enhanced BSE-risk in the offspring of BSE dams involves a low level of direct maternal transmission in the late stages of the incubation period. 10. __In view of the findings of the analyses that are summarised above, the subcommittee concludes that there is some evidence for direct maternal transmission of BSE at a low level, but some variation in genetic susceptibility to BSE following feed-borne exposure may occur. The risk of transmission of BSE from dam to calf is likely to be less than 10%, and appears to be confined. to animals born after the onset of BSE in the dam or up to two years beforehand. This level of transmission is not sufficient, by itself, to perpetuate BSE in the cattle population and is likely to have only a minor effect on the rate at which the incidence of BSE declines. It is inevitable that cases infected via animal feed will continue to appear in diminishing numbers for several years. Therefore, although the number of cases infected maternally will be small, they may represent an increasing proportion of the remaining cases detected. 11. Given the evidence that variation in genetic susceptibility may have contributed to the results of the cohort study, and of the importance of genetic factors in TSEs in other species, the subcommittee considers that further research is necessary to clarify whether or not variations in the PrP gene or other genes may be influencing the transmission of, or susceptibility to, BSE in cattle. Research should seek to identify polymorphisms of the PrP gene which may be associated with BSE susceptibility, including stored samples from the cohort study. There should also be a search [AVMC1]for other genetic markers, outside the PrP gene, which may be associated with an increased BSE risk in cattle. SEAC CONCLUSIONS OF 23 MAY 1997 The Committee reviewed the position since the advice it tendered to Government in July 1996 on the precautions necessary to protect the public from the theoretical risk of BSE in sheep. At that time it recommended action on brains, which was taken by the UK Government in September 1996, and that the issue be considered further with EU partners. The Committee noted that the EU Commission tried to introduce measures which would go beyond those adopted in the UK in that they would: 1) prohibit the use in human or animal feed of: (a) the spinal cord from older sheep and goats (those with one or more permanent incisors); (b) the spleen from all sheep and goats;
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