Professor James Ironside is Professor of Clinical Neuropathology at the University and Director of the MRC Network of UK Brain Banks. Prions attack the brain, leading to such diseases as CJD in humans and BSE in cattle. Unlike bacteria and viruses, prions cannot be seen under a microscope, so we have to use detective skills to identify the traces they leave. There is no blood test to detect prion infections and no cure exists at present. This lecture will detail the detective work used to try to find answers to these problems. This lecture is part of the Medical Detectives, a series of public lectures that show how keen detective work is still essential for 21st century doctors: http://www.ed.ac.uk/news/events/medical-detectives/ Recorded on Thursday 4 November 2010 in the Anatomy Lecture Theatre at the University of Edinburgh.