Fears that mad cow disease, or bovine spongiform encephalopathy (BSE), might be spreading to humans have grown over the past couple of years because the incidence of the human disease had been rising since the Creutzfeldt- Jakob Disease Surveillance Unit starting compiling statistics in 1990.
But the researchers believe that many elderly people are now being properly diagnosed as having CJD where once they might simply have been categorised as going demented in old age.
Dr Rob Will, from the Western General Hospital in Edinburgh, who heads the unit, said yesterday that there had been a significant increase in people aged 75 or over being diagnosed as having CJD. This probably did not reflect a real increase in the number of cases, but simply a better identification of the cause of death.
Dr Will was speaking at a press conference in London to mark publication of the unit's third annual report. It remains a rare condition: in 1993, there were 40 cases, whereas in 1992, there were 51. Other European countries are also studying the incidence of CJD, although widespread mad cow disease is largely confined to Britain and has not spread to the continent. The rate of CJD in Britain is similar to that in other European countries.
Dr Will said: 'We do not believe that these results demonstrate any risk to the human population from BSE.'
However, CJD takes a long time to develop from initial infection to clinical symptoms of disease. Dr Will warned that, because of the lengthy incubation period, the unit's study would have to continue for at least 20 years before the possibility of a link between the bovine and human diseases could be conclusively proved or disproved.
The statistics also showed an apparent association between the regular eating of veal or venison and the incidence of CJD. But this was not evidence of cause and effect, Dr Will said.
'If you eat it (veal) more than once a year this is apparently associated with a 13-fold increased risk of CJD,' but, he said, the result is almost certainly a statistical freak and the result of unconscious bias in the way that family members recalled the dietary habits of those who had died of CJD.
Last year's report had shown a possible association between CJD and the eating of black puddings. This year, however, the statistical connection had disappeared.
Dr Kenneth Calman, the Chief Medical Officer, said: 'I continue to be satisfied that there is no scientific evidence of a link between meat eating and development of CJD and that beef and veal are safe to eat.'Reuse content