The cause of the original case or cases of BSE is currently unknown. Sheep scrapie or a previously undetected bovine transmissible spongiform encephalopathy (TSE) that arose spontaneously have long been considered as candidates. However, no convincing evidence to support these proposals has been found.
Alan Colchester (University of Kent, UK) and Nancy Colchester (University of Edinburgh, UK) propose a new theory consisting of three hypotheses, that human TSE-contaminated material was the cause of BSE; that this was transmitted orally via animal feed; and the infective material originated from the Indian subcontinent. The authors present substantial circumstantial evidence to show that human material was imported into the UK from India with other animal remains for the production of animal feed over a long period. They also argue that human TSE and BSE strain characteristics have sufficient similarities to be consistent with their hypothesis.
Professor Colchester concludes: "Further investigations are needed into the sources of animal by-products used in animal feed manufacture, and into the transmissibility of human TSEs to cattle… Within as well as between countries, it will be particularly important to establish cooperation between public health, agricultural, and industry organisations, as well as researchers, to try to ensure that further investigations are sufficiently thorough. WHO might be the best international body to coordinate this collaboration."
In an accompanying comment Susarla Shankar (National Institute of Mental Health and Neurosciences, Bangalore, India) states: "So far not a single case of BSE or scrapie had been reported from India, except for one case of scrapie from the Himalayan foothills in a sheep, which was probably imported…Scientists must proceed cautiously when hypothesising about a disease that has such wide geographic, cultural and religious implications. We agree that the idea proposed by the Colchesters needs to be probed further. Facts to support or refute their hypothesis now need to be gathered with urgency and great care."
Contact: Professor Alan Colchester by calling Posie Bogan, Media & Communications Manager, University of Kent T) +44 (0)1227 823581/ 01227 823 100
Comment: Dr. S.K. Shankar, Professor and Head, Department of Neuropathology, NIMHANS, Bangalore 560 029, Karnataka, India. T) 91-080-26995130 shankar@nimhans.kar.nic.in
Journal
The Lancet