A NEW FORM of CJD identified in Britain six months ago is probably caused by eating BSE-infected meat, new research indicates. In a paper in today's issue of the science journal Nature, a team at Imperial College in London says it has found the first direct evidence that BSE has crossed the species barrier and been transmitted to humans. However, the study concludes that the majority of CJD cases is not linked to BSE.
The Department of Health said last night that it would refer the new findings to its advisory group on CJD so that the evidence could be fully evaluated.
To date, 14 cases of the "new variant" form of CJD have been confirmed in Britain, most of them in the past 12 months. Called vCJD, it affects younger people (the average age at death is about 27). Patients also take twice as long to die (13 months compared with six months for sporadic CJD).
The latest research confirms that vCJD is different from other known forms of the disease. Although the scientists say they believe it is caused by BSE, their study sheds no light on how effective the transmission is. They cannot therefore indicate how many more cases of vCJD can be expected.
Significantly, however, they also report that sporadic CJD, which currently accounts for the majority of CJD cases, does not appear to be associated with BSE, despite initial fears among the public that this could be so.
The scientists studied the "biochemical signature" of the rogue prion proteins thought to be the root cause of these diseases. Samples were taken from 26 people with sporadic CJD, six with iatrogenic CJD (acquired, for example, during a transplant operation) and 12 people with vCJD.
These "signatures" were compared to those from cattle, cats and antelope which had BSE and from macaque monkeys infected with BSE experimentally. They report said that the signatures seen in the 12 cases of vCJD were unique. Most importantly, the vCJD signature was the same as that seen in the animals with BSE.
The scientists suggest that it is "extraordinarily unlikely" that the same rogue form of the prion protein could occur spontaneously in 12 individuals. They conclude that there has to be a common source and that this is presumably BSE-infected meat.
The team hopes its technique for comparing protein signatures may one day form the basis for a diagnostic test for the disease.