Volume 2: Science
2. The Spongiform Encephalopathies - knowledge existing in 1986
Introduction

2.1 In 1986, when the disease later known as BSE was first recognised in cattle, much knowledge had already accumulated, in the UK and elsewhere, about the group of diseases known as the transmissible spongiform encephalopathies (TSEs). Extensive work had been carried out on scrapie, a TSE commonly found in sheep in the UK, as well as on similar diseases in other animals and in humans. Parallels had already been drawn between scrapie and human TSEs, as early as 1959. ¹ This existing knowledge was available for use by those investigating the new disease.

2.2 This chapter concentrates on the state of scientific knowledge in 1986, highlighting the factors relevant to those investigating BSE. However, several of the conclusions reached by 1986 have subsequently been found to be incorrect. Where misconceptions have been corrected by subsequent research, this has been indicated in the text.

2.3 We begin by describing the animal and human TSEs known in 1986. We then explain what was known about the nature of the TSE agent and its mode of replication, before moving to genetic aspects, transmission and pathogenesis. The chapter ends with a brief account of post-1986 knowledge of prion gene mutations in human TSEs.