NEWS: Atypical strain of Mad Cow reported -- Kansas City Star06/12/06

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Posted on Mon, Jun. 12, 2006

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'Atypical' strain of mad cow reported

*Two U.S. cases have scientists pondering whether the disease can

develop spontaneously.*

*By LIBBY QUAID*

*The Associated Press*

 

*WASHINGTON | - *WASHINGTON | Two cases of mad cow disease in Texas and

Alabama seem to have resulted from a mysterious strain that may appear

spontaneously in cattle, researchers say.

 

Government officials are trying to play down differences between the two

U.S. cases and the mad cow epidemic that led to the slaughter of

thousands of cattle in Britain since the 1980s.

 

It is precisely these differences that are complicating efforts to

understand the brain-wasting disorder, known medically as bovine

spongiform encephalopathy, or BSE.

 

"It's most important right now, till the science tells us otherwise,

that we treat this as BSE regardless," said the Agriculture Department's

chief veterinarian, John Clifford.

 

The Texas and Alabama cases -- confirmed last year and this year,

respectively -- are drawing international attention.

 

At a meeting in London last month, experts presented research on the

U.S. cases and on similar ones in Europe.

 

These cows appear to have had an "atypical" strain that scientists are

only now starting to identify. Such cases have been described in about a

dozen cows in France, Italy and other European countries, as well as in

Japan.

 

In the two U.S. cases, researchers did not detect the telltale spongy

lesions caused by prions, the misfolded proteins that deposit plaque on

the brain and kill brain cells. Also, the prions in brain tissue samples

from the Texas and Alabama cows seemed to be distributed differently

from what would be expected to be found in cows with the classic form.

 

Laboratory studies on mice in France showed that both the classic and

atypical strains could be spread from one animal to another. But

scientists theorize the atypical strain might have infected cattle

through an unusual way.

 

Mad cow disease is not transmitted from cow to cow like the flu. It is

thought to spread through feed, when cows eat the contaminated tissue of

other cattle. That happens when crushed cattle remains are added to feed

as a protein source. This practice ended in the U.S. in 1997.

 

Some scientists are raising the possibility that the atypical strain

might happen spontaneously in cattle. The Texas and Alabama cows were

older animals.

 

No matter what the origins might be of an atypical strain, the

government says, there is no reason to change federal testing or

measures that safeguard animals and people from the disease.