June 12, 2006

 

Researchers say mad cow disease may occur spontaneously

 

 

Two previous cases of mad cow disease in Texas and Alabama seem to have resulted from a strain that could appear spontaneously in cattle, researchers say.

 

Government officials are trying to play down differences between the two US cases and the strains that killed thousands of cattle in Britain in the 1980s.

 

However, it is those differences that are complicating efforts to understand the disease, researchers said.

 

Still, the strains are regarded as one and the same unless proven otherwise, the Agriculture Department's chief veterinarian, John Clifford said.

 

The Texas and Alabama cases - confirmed last year and this year, respectively - are piquing the interests of scientists.

 

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.

 

In the two US cases, researchers did not detect the usual lesions caused by prions, the misfolded proteins that deposit plaque on the brain and kill brain cells. The prions in the US cows also seemed to be distributed differently from the typical form.

 

Scientists think the atypical strain might have infected cattle through a different channel other than feeds.

 

Mad cow disease is believed to spread through feed contaminated with tissues of other cattle.

 

Humans can get a related disease, variant Creutzfeldt-Jakob Disease, by eating meat contaminated with mad cow. While mad cow usually afflicts older cattle, mad cow in humans affects younger people.

 

However, a more common form of CJD, unrelated to mad cow, can happen spontaneously and is reported in nearly 300 people in the US each year. This form occurs mostly in older people.

 

Some scientists say that the atypical strain might happen spontaneously in cattle.

The Texas and Alabama cows were older animals, as were some of the other animals in Europe with seemingly atypical cases.

 

The US government said it has no plans to change federal testing or measures at the moment.