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From: TSS ()
Subject: Suspect US animal may have rare mad cow strain
Date: June 16, 2005 at 11:14 am PST

Suspect US animal may have rare mad cow strain

Thu June 16, 2005 2:05 PM GMT-04:00
By Randy Fabi

WASHINGTON (Reuters) - A rare and puzzling form of mad cow disease that some believe arises spontaneously may have afflicted the U.S. animal that tested positive for the ailment last week, a senior Agriculture Department scientist told Reuters.

The USDA has sent a sample of the suspect animal's brain to an internationally recognized laboratory in England to pinpoint if the animal has bovine spongiform encephalopathy (BSE). The USDA said it could take another week to complete final tests.

Juergen Richt, a member of the USDA team in Ames, Iowa that already tested the animal, said the unusual test results could point to a relatively new strain of BSE that infects cattle sporadically, instead of from eating contaminated food.

But he said it was too early to draw a conclusion about the aging, beef animal was slaughtered last November and incinerated because it was a "downer" unable to walk, and banned from the human food supply.

"Nobody knows for sure yet, but the theory is it could be a spontaneous bovine disease," said the veterinarian medical officer. "There are some hallmark signs that this could be an atypical case."

The only confirmed U.S. case of mad cow disease was found in a Holstein dairy cow in Washington state in December 2003.

Since then, scientists in France, Italy, Japan and Belgium have discovered at least two new BSE strains that differ from the outbreak that swept European herds in the 1980s.

Cattle brains infected with the two new strains resemble brains of humans diagnosed with classical Creutzfeldt-Jakob disease, a rare and fatal form of dementia that infects one in a million people worldwide, researchers said.

Some experts believe the new BSE strains could arise naturally within cattle, for reasons that remain unknown.

"The jury is still out on this," Richt said. "Is it infectious? That's the $100,000 question."

Experts expressed concern about the possibility of an animal developing BSE spontaneously.

"If this is a sporadic case, then it would be very important to keep all of our current safeguards in place, and put in place additional ones," said Jean Halloran, director of food policy at Consumers Union.

More than 140 human deaths have been blamed on the original BSE outbreak in Europe, from people who ate contaminated beef. Since that outbreak, in the 1980s, most nations have banned the use of cattle remains as a protein supplement in cattle feed.


Richt said a naturally occurring BSE strain would probably infect other cattle. "Sporadic BSE in cattle would most likely be infectious for other cattle, but no one can tell you yet if it's infectious for humans," he said.

Scientists were years away from answering these questions, Richt added. But he said any carcasses infected with a new strain should be treated as any other BSE-infected animal and segregated from human and animal feed supplies.

Richt considered the current suspect animal a good candidate for the atypical strain, with conflicting test results similar to cases in Japan and Belgium.

A rapid screening test on Nov. 15 returned inconclusive results. A more sophisticated procedure, immunohistochemistry (IHC) tests, cleared the animal of any infection.

But last week, the USDA's office of inspector general ordered a third round of testing. The Western blot procedure used in Japan and Europe showed a "weak positive."

In atypical cases, weak test results were a result of a wider distribution of the abnormal or misshaped prion protein, the main signature of the disease, in an infected brain.

While USDA has refused to say where the animal was detected, some published reports say it was found in southern Texas, half a continent away from the only proven U.S. case.


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