Bovine Spongiform Encephalopathy: Atypical Pros and Cons

摘要

Transmissible spongiform encephalopathies (TSEs) are fatal neurologic diseases that affect several mammalian species including human beings. Four animal TSE agents have been reported: scrapie of sheep and goats; chronic wasting disease (CWD) of deer,elk, and moose; transmissible mink encephalopathy (TME) and bovine spongiform encephalopathy (BSE). In comparison with contagious bacterial, viral and parasitic infectious diseases, TSEs typically do not present with high morbidity or mortality rates inlivestock, wildlife or human populations. The TSEs, however, remain important because of public health and international or domestic trade issues involving movement of animals. In response to the discovery of BSE, governments around the world began investing in research to determine the origin of BSE and the host range of the recognized TSEs. The prevailing theory at the time of the BSE discovery was that it had resulted from transmission of scrapie from sheep to cattle. Once the original interspeciestransmission event had occurred it was then amplified by the subsequent feeding of meat and bone meal (MBM), a supplement that normally contains central nervous system (CNS) tissues, which inevitably became contaminated with CNS tissues from BSE affected cattle. Such practice precipitated more BSE cases, thus resulting in greater volumes of contaminated MBM supplement assisted by growing inventories of contaminated MBM prior to its discovery.