§ Mr. Martyn JonesTo ask the Minister of Agriculture, Fisheries and Food what plans he has to test randomly the brains of slaughtered dairy cows for BSE. [66503]
§ Mr. RookerA study of brain tissue from cattle slaughtered in the Over Thirty Months Scheme was started on 4 January 1999. The aim is to collect, by the end of March, samples from 4,000 animals. The brain samples will be tested for the presence of abnormal prion protein (PrPSc) by two or more of the recently developed diagnostic tests, and also studied by histopathology for evidence of vacuolation. In compliance with a recommendation from SEAC, the study is being confined, in so far as is possible, to animals 5 years of age or over. 5 years is the average incubation period of BSE and PrPSc has been detected in brain tissue only quite late in the BSE incubation period.
§ Mr. Martyn JonesTo ask the Minister of Agriculture, Fisheries and Food what methods are available to confirm the diagnosis of transmissible spongiform encephalopathy using brain materials from slaughtered animals. [66499]
§ Mr. RookerAt the moment, all diagnostic tests for BSE using brain tissue rely upon the infectious agent having reached the central nervous system. Current evidence indicates that this event occurs late in the incubation period, shortly before clinical onset. Any diagnostic test applied earlier in the incubation period is therefore likely to produce a negative result, even if the animal is infected. Once infectivity has reached the central nervous system, several diagnostic options are theoretically possible although none will be absolute. In other words, there may be some false negative results and interpretation of positive results is still open to question, given that some of the available tests have not been fully validated. The options available include mouse inoculation, which could take up to three years to give a result; histopathological examination of the brain stem; extraction of "scrapie-associated fibrils"; or one of a range of immunologically based tests for the detection of abnormal prion protein. None of the latter have been fully validated as yet.
§ Mr. Martyn JonesTo ask the Minister of Agriculture, Fisheries and Food if he will list the percentage of suspected BSE cases that have been subsequently confirmed in each year from 1988 to 1998. [66504]
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§ Mr. RookerOf the cases placed under restriction in each calendar year and subsequently slaughtered, the following percentages were confirmed:
Percentage Year of restriction Confirmation rate for Suspected BSE cases 1988 91.92 1989 88.54 1990 85.22 1991 86.24 1992 85.00 1993 83.66 1994 83.40 1995 83.36 1996 78.95 1997 81.30 1998 177.16 1The 1998 figure is provisional; some results are still pending. It is unlikely that the full figures for 1998 will be available before the end of May 1999. Note:
Data as at 8 January 1999