WHAT ARE PRION DISEASES?

Prion diseases are otherwise known as transmissible spongiform encephalopathies (TSE), which are fatal neurodegenerative disorders that occur in many species of mammal, including humans. They include the cattle disease bovine spongiform encephalopathy (BSE) and the human form Creutzfeldt–Jakob disease (CJD). The oldest recognised TSE is scrapie in sheep and goats which has been recorded in these animals albeit under different names since the eighteenth century. Other species that have since been diagnosed with a specific form of TSE disease are included in the list shown in Table 13.1. The list has been divided into two groups, those that are host specific and those that have occurred as a consequence of the United Kingdom's highly publicised BSE outbreak of the 1980s–1990s.

The name TSE is derived from the fact that these diseases are transmissible from one animal to another and among species, and they are pathologically defined by the appearance of spongelike vacuolation in the gray matter of the brain.

Experimental animal transmission studies in primates and rodents have been performed using material from cattle diagnosed with BSE. This has indicated, to the acceptance of the majority of the scientific community, that the latest form of TSE in humans, variant Creutzfeldt–Jakob disease (vCJD), is attributable to infection by the bovine prions found in cases of cattle with BSE. The route of infection from contaminated bovine products is as yet undetermined but is most probably through dietary consumption.