What went wrong in BSE? From prion disease to public disaster

The recent report of 10 cases of a new variant of Creutzfeldt-Jakob disease (CJD) which could be related to bovine spongiform encephalopathy (BSE) has precipitated alarm throughout Europe. The beef trade in the UK has collapsed and the European beef market has been seriously damaged. What went wrong? Much of the difficulty of handling the BSE epidemic arose from the 4-5 year incubation period which made it difficult to ascertain whether measures taken to contain the epidemic had been effective. Public consternation and scientific equivocation arose because these prion diseases are unlike any other group of infectious diseases. Rather than being caused by a conventional micro-organism, the primary pathogenic event consists of the transformation of a normal protein (the prion protein) into an abnormal form, which can transmit disease. Prion disease is endemic in humans and sheep where it is associated with polymorphisms or mutations within the prion protein gene. Although the disease in these cases arises spontaneously, it produces an infectious prion protein. Under certain circumstances, abnormal prion protein contaminates other animals or humans resulting in epidemics of acquired prion disease. This review describes the events of the BSE epidemic and considers the difficulties in assessing the current risk to human health.