BSEの現況

The current situation of BSE（bovine spongiform encephalopathy）

　BSEは肉骨粉の給餌により広がったものと考えられている。2000年秋以降，BSE初発国が相次いで現れ，日本でも2001年9月に初発例が見いだされた。その背景には，1988年以後，英国から多量の肉骨粉が世界各国に輸出され，世界的BSE汚染が起きていることが存在する。BSE対策における食品の安全確保は，特定危険部位の除去と迅速BSE検査に基づいている。それらの科学的根拠についての解説を行った。

　BSE is considered to be caused by oral infection through the meat and bone meal（MBM）. Since late 1980s, large amount of MBM was exported from UK until 1996. Recent increase in number of countries where the first case of BSE is found indicates the spread of BSE worldwide through such export. In Japan, active surveillance for BSE was initiated in April 2001 to confirm the freedom from BSE by testing a total of 300 cattle with neurological signs. However, number of samples collected at the end of April was so few, therefore the criteria for neurological signs were extended as to include the animals that cannot stand. Incidentally, one cattle that could not stand was found at slaughter house, and was confirmed to be BSE-positive by both western blot and immunohistochemical staining for abnormal prion protein, albeit the histopathological changes in the brain were minimal. Subsequently established measures for the food safety consist of the removal of specified risk materials and testing the brain stem by rapid ELISA system on all cattle regardless of ages at slaughter house. Comprehensive ban of MBM was also started to prevent the spread of BSE among cattle. Scientific basis for these safety measures as well as remaining issues are mentioned.