Mad cow strain found in Tulare County mysterious
Much is unknown about type of infection found last week in dairy cow.

By Barbara Anderson – The Fresno Bee 

출처 : Sunday, Apr. 29, 2012 | 12:05 AM Modified Sun, Apr 29, 2012 09:40 AM

http://www.fresnobee.com/2012/04/29/2818170/rare-mad-cow-strain-found-in-tulare.html

Federal officials have been quick to reassure the public that there is no health threat from the mad cow disease discovered in the carcass of a Tulare County dairy cow.
But there is a lot they don’t know about the type of infection in that carcass — including how the cow got the disease, how long it was ill, and the risk to the public if that strain gets into the food supply.
The infection in the 10-year-old cow was found when the carcass was brought to a Hanford processing plant for rendering. Its brain was among those randomly screened for the disease. The carcass was not destined for human consumption.
The U.S. Department of Agriculture said lab tests found a rare “atypical” strain of bovine spongiform encephalopathy, which attacks the brain and is fatal to cows. The strain — one of two rare types — is different from the more common “classic” mad cow disease, which has been spread in the past by feed contaminated with animal protein. Such feed was banned in the United States in 1997.
The good news, researchers and agriculture officials say, is that the two strains of atypical mad cow disease are very rare. Officials don’t know what causes atypical mad cow disease, but it appears to occur sporadically and maybe even spontaneously. And the current method for screening cattle for the disease has been able to catch it.
But all of the unknowns about the disease have some people worried that more widespread testing of cattle is needed to keep diseased beef out of the food supply.
“We have concerns and questions about the fact the USDA is stating this is definitely not something the animal contracted from food,” said Florence Kranitz, president of the Creutzfeldt-Jakob Disease Foundation, an organization for people with degenerative brain diseases and their families.
A nagging question, Kranitz said, is how infectious is the disease? Some studies have indicated that atypical mad cow disease could be a more serious health risk than classic mad cow disease if it enters the food chain of animals or people, she said.
Officials with the U.S. Department of Agriculture said consumers are being protected.
“Our surveillance system is effective in identifying animals that are at risk [of mad cow disease] and will tell us if there is a problem in a herd,” agency officials said by email, responding to questions from The Bee.
Atypical mad cow cases have not been high on the government’s radar. Since the 1990s epidemic of classic mad cow disease, governments worldwide have focused on stamping out the brain-wasting disease in cattle by banning the feeding of animal protein.
The contaminated feed has been linked to not only the infection in cattle but to a human degenerative brain disease known as variant Creutzfeldt-Jakob in people who ate infected beef.
The effort has been a success: Classic cases have dropped — from 37,311 cases worldwide at its peak in 1992 to a total of 29 cases worldwide in all of 2011, the USDA said.
Now, the few incidences of atypical mad cow disease have gained in importance.
Of the four mad cow cases in the United States since 2003, three have been of atypical origin, including the Tulare County cow — California’s first case of mad cow disease. The one classic mad cow case was in a cow brought in from Canada.
The discovery of the three atypical cases shows the surveillance system works, the USDA said.
Federal inspectors randomly sample carcasses at rendering plants, looking for the tell-tale misshapen proteins, called prions, that leave spongy holes in the cows’ brains.

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