Italian scientists have found a second form of mad cow disease more closely resembling a similar human disease than the one usually found in cattle, it was announced today.

A study of eight cows with mad cow disease found that two had brain damage resembling that in human victims of the standard "sporadic" form of CJD.

Salvatore Monaco, the new study's lead author, told the Associated Press he believed that the incidence among cattle with mad cow symptoms could be as high as 5%.

The unusual strain was discovered when the two cows, aged 11 and 15, were subjected to tests required for all cattle that are more than 30 months old and destined for human consumption.

In addition to the holes in the brain caused by BSE - the form of disease most often found in cows - the Italian researchers found, in their sample, an accumulation of the amyloid brain plaque that is an indication of Alzheimer's disease.

The scientists have named the new form BASE (bovine amyloidotic spongiform encephalopathy) to differentiate it from as BSE (bovine spongiform encephalopathy).

However, while "sporadic" CJD and the new form found in cows share several characteristics, the researchers have cautioned against assuming a link between the two.

"We don't know if this disease is passed to humans," Dr Monaco said.

A US brain disease expert said that the finding did not indicate an increased threat to humans.

Paul Brown, of the US National Institute of Neurological Disorders and Stroke, said that there should be an increase in the incidence of CJD if the new form of the disease was affecting humans.

Sporadic CJD is distinct from the human variant of the disease, which is linked to eating meat from BSE-infected cows.