- WASHINGTON - Rogue proteins
like those that cause mad cow disease -- found previously only in brain,
nerve and lymph tissues -- have now been located in the liver, kidney and
pancreas in a study of rodents.
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- While the discovery raises the possibility that similar
proteins could move into unanticipated parts of farm animals that have
similar diseases, it is not a reason for alarm, says researcher Adriano
Aguzzi of the University Hospital of Zurich, Switzerland.
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- But, he adds, "There is reason to reappraise critically
the way regulations that are already in place" are enforced.
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- Sick animals such as sheep and cows should not enter
the human food chain, Aguzzi, the lead researcher in the study, said in
a telephone interview.
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- "I think what is probably worth doing is to recheck
whether all these regulations are implemented properly," he said.
"But, I think this is nothing that should provoke a wave of panic."
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- Rogue proteins called prions are blamed for several brain-wasting
diseases, including mad cow disease, scrapie in sheep and variant Creutzfeldt-Jakob
disease in humans.
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- These proteins had only been found in the brains, spinal
cord and lymph tissues of infected people and animals. But Aguzzi's report,
being published online Thursday by the journal Science, indicates that
in at least some cases they can move to other parts of the body.
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- Inflammation, characterized by swelling, redness and
pain, occurs in a number of diseases, such as hepatitis, which affects
the liver.
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- "I think it certainly raises questions as to the
current classification of risk organs, which essentially says the brain
and lymphatic tissue is at risk, whereas everything else is rather safe,"
Aguzzi said. "So, I think that in the case of an inflammatory condition,
I think that is no longer valid."
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- The finding "reinforces that you never say never,"
said Dr. William Hueston, director of the University of Minnesota's Center
for Animal Health and Food Safety.
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- Hueston, who was not part of Aguzzi's research team,
agreed that the finding isn't cause for alarm, saying it reinforces the
reasons for inspecting animals in the food chain.
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- Dr. Robert B. Petersen, a professor of neuropathology
at Case Western Reserve University in Cleveland, agreed that any risk is
low since screening procedures would identify infected animals.
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- In addition, considering the low incidence of prion diseases,
"it is unlikely that you would find an animal with chronic viral or
bacterial infection and prion infection simultaneously," said Peterson,
who was not involved in Aguzzi's research.
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- Jim Rogers, of the Agriculture Department's Animal and
Plant Health Inspection Service, said the agency already targets high-risk
animals and won't need to change its procedures.
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- In the study, Aguzzi's team, which included researchers
at the Institute of Neurology in London and at Yale University, raised
mice that had chronic inflammatory disease of the liver, pancreas or kidney.
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- These mice were injected with prions from sheep suffering
from the disease scrapie, and when the mice were studied the researchers
found at least some of the prions had accumulated in the diseased organs.
Aguzzi said he is planning similar experiments on sheep.
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- Mad cow disease is formally known as bovine spongiform
encephalopathy, or BSE. The brain-destroying illness raised great concern
when a form of it passed to humans in England in the 1980s and 1990s. It
has killed more than 140 people in Britain and at least 10 others in other
parts of the world. The only U.S. death, last June, was a woman who had
been infected in England years earlier.
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- When BSE is passed into humans it is known as variant
Creutzfeldt-Jakob disease. There is also a brain-wasting disease called
sporadic Creutzfeldt-Jakob disease that occurs in humans, but is not caused
by BSE. Both, however, are caused by prions, proteins that fold incorrectly.
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- Only a single case of mad cow disease has been reported
in the United States, in Washington state, prompting federal regulators
to ban certain portions of cows from human food and to tighten rules on
use of sick animals.
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- The research was supported by the Swiss Federal Office
for Education and Science, Swiss National Science Foundation, Swiss National
Center for Competence in Research, University of Zurich, a grant from the
Catello family, the Association for the Promotion of the Academic New Generation,
the Medical Research Council of the United Kingdom and the U.S. National
Institutes of Health.
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