Dr Dealler, a senior registrar at Burnley General Hospital, has made a detailed study of the epidemiological risks to humans, assuming varying levels of infectivity from BSE-infected beef. In a wide-ranging study, he has also visited meat markets, auctions and abattoirs to find out at first hand whether farmers and slaughterhouse workers were really following the Government's guidelines. He often found that they were not.
Richard Lacey, a microbiologist at the University of Leeds, has claimed since 1989 that BSE would be passed on to humans, and that an epidemic was on the way.
However, he was repeatedly dismissed as a scaremonger, even though he had been proven correct in previous years when he warned of the risks posed by salmonella. He is predicting that hundreds of thousands of people could develop CJD as a result of consuming BSE-infected foods.
But colleagues say that Professor Lacey was too ready to talk to the media when his research was incomplete.
Scientists generally prefer to carry out their arguments through the pages of scientific journals rather than through newspapers and television channels.
Dr Narang is also a microbiologist. He has alienated many other scientists by putting forward a theory for BSE - that it is caused by a "slow virus" which takes decades to act - that conflicts with a number of peer-reviewed experiments.
Based in Newcastle, he is now funded by a private businessman, having been fired from the Government's Public Health Laboratory Service in the 1980s.
He claims to have developed a urine test for both BSE and CJD which can diagnose the disease while the victim is still alive. He claims, though, that he has been the victim of a witch-hunt in which his car's tyres have been slashed and his house broken into.
However, other scientists point to what they see as inconsistencies in Dr Narang's work. One is that BSE has not been linked to any cases of CJD until 10 unusual deaths in humans, apparently from a new strain of the disease, which occurred in the past two years. This, they say, shows that Dr Narang's evidence for a link in 1990 cannot be valid.Reuse content