msnbc.com staff and news service reports
updated 2/17/2004 7:14:24 PM ET 2004-02-18T00:14:24

Italian scientists have found a second form of mad cow disease that resembles a human form of Creutzfeldt-Jakob Disease, rather than the cow form of the illness.

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Bovine spongiform encephalopathy (BSE), the fatal brain ailment more commonly known as mad cow disease, and human CJD are caused by different forms of mutant proteins called prions. Hundreds of people, primarily in England, have suffered from what is called variant CJD, a human form of BSE thought to be acquired by eating meat from infected cows. No Americans cases of variant CJD have been documented.

Now, the team of Italian researchers reports a study of eight cows with mad cow disease found that two of them had brain damage resembling that found in human victims of the standard form of CJD, known as sporadic CJD. The researchers' cows were infected with prions that resembled those found in human cases of sporadic CJD, rather than the variant caused by eating infected meat.

Salvatore Monaco, lead author of the new study, said the findings may indicate that cattle can also develop a sporadic form of the disease, but it might also be a new foodborne form of the illness.

To that end, the finding highlights a long-standing mystery among researchers about the causes of sporadic CJD, which accounts for more than 80 percent of CJD cases worldwide.

While variant cases of the illness have been traced back to tainted meat, many scientists believe the sporadic form that has been found all over the world is caused by spontaneous genetic mutation; to date, no specific cause for sporadic CJD has been documented. About one in a million people in the United States are found to have traditional CJD.

But the discovery of a similar form of the disease in cattle leaves open the possibility that the sporadic form of the disease could be transmitted through food. If such a connection were to be confirmed, it could drastically change governments' risk assessments for mad cow disease.

"There's a lot of science that has to be done in order to make a link, if one exists, but it does open that concern," said Dr. Neil Cashman, a professor and researcher at the University of Toronto's Center for Research in Neurodegenerative Diseases.

However, Dr. Paul Brown of the National Institutes of Health said the finding does not indicate an increased threat to humans.

If a new form of mad cow disease had been affecting humans, Brown suggested, it should be reflected in an increased incidence of CJD. Yet European scientists tracking all cases of sporadic CJD for the last decade have not found an increased incidence, said Brown, an expert in prion diseases at the National Institute of Neurological Disease and Stroke who was not part of the research team.

Similarities to human strain
Both the human and cattle diseases cause holes to form in the brain. The Italian researchers found that, in addition to the holes, two cows had an accumulation of amyloid plaque in their brains. Amyloid plaques are an indication of Alzheimer's disease in humans. They have also been found in people with sporadic CJD but had not been found in cattle, the researchers said.

Sporadic CJD functions not unlike degenerative brain diseases like Alzheimer's. It results in a gradual breakdown of neurological functions and, for most patients, death within a year of the disease's onset. There is no known cure for any form of CJD.

The Italians named the new form of the disease BASE, similar to mad cow disease's official acronyn BSE.

"Although observed in only two cattle, the BASE phenotype could be more common than expected," they reported.

Monaco said in an e-mail interview with The Associated Press that he believes the incidence could be as high as 5 percent among cattle with mad cow symptoms.

But while human CJD and BASE share several characteristics, the researchers and others who reviewed their work cautioned against assuming a link between the two.

The findings of the team led by Monaco, of the Department of Neurological and Visual Science, Policlinico G.B. Rossi, in Verona, Italy, are reported in this week's online edition of Proceedings of the National Academy of Sciences. 

Brown said there have also been some unpublished reports from Japan of cows with a different form of mad cow disease.

And in 1998, three of the Italian researchers documented a case of CJD in an Italian man whose cat was simultaneously stricken with a feline form of the disease.

Cattle are believed to develop BSE from eating infected tissues of other animals. Such feed has now been banned in many countries, including the United States -- which in 1997 banned its use on cows and some other livestock but still allows it on certain animals.

However, Cashman noted, the Italian scientists' discovery resurfaces earlier considerations that the first case of BSE might have been spontaneous generated, rather than a result of feeding cattle protein to other cows, as has been suspected.

'More suspicious'
Dr. Michael Hansen, who researches prion diseases for Consumers Union, said the new findings cast additional skepticism on the long-held notion that all mad-cow cases stem from the same aberrant proteins uncovered in British cattle. While researchers have generally drawn a clear line between sporadic and variant forms, more attention may now be paid to possible links between the two types.

"People always thought it strange that all these cases of mad cow so far were one strain," Hansen said. "It doesn’t prove anything, but it's more suspicious. We need to pay more attention to all forms of CJD," not simply the form tied to mad cow disease.

The first case of mad cow disease in the United States was reported in December in Washington state, involving a cow imported from Canada.

An investigation seeking other cattle from the same herd ended last week with Agriculture officials saying they had located all but 11 suspect animals and concluding the rest could not be found. U.S. officials plan to test 40,000 head of cattle this year for signs of mad cow disease, out of some 35 million slaughtered annually.

By comparison, the Italian scientists discovered the aberrant cases through the use of rapid BSE testing kits used to test 1.6 million Italian cows between January 2001, when the Italian government mandated testing on all older cattle, and August 2003.

The use of rapid tests and of more widespread testing on the U.S. herd has been widely suggested. Most recently, a panel of House lawmakers Tuesday told the U.S. Department of Agriculture that it needed to expand its testing to at least 200,000 head of cattle.

The USDA has said the current plans for testing are sufficient.

The researchers in Italy did not indicate that the cows in the study exhibited outward signs of illness at slaughter, though they were between 5 and 15 years old -- older than most cattle intended for human consumption.

MSNBC's Jon Bonné and The Associated Press contributed to this report.

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