- NEW YORK (Reuters
Health) - New research suggests that the errant proteins that cause "mad
cow" disease in cattle and a similar brain disorder in humans can
travel from the tongue to the brain and vice versa.
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- The experiments were performed in hamsters, and did not
use the same type of abnormal proteins that cause mad cow disease.
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- However, if similar findings are discovered in animals
that can sicken humans, it would suggest that eating beef tongue and products
that contain beef tongue may put people at risk of the deadly human ailment
known as new variant Creutzfeldt-Jakob disease (vCJD).
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- What's more, the researchers found that placing the prions
on a small wound in the tongue was a highly efficient way to spread the
disease, more so than actually eating the proteins.
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- Mad cow disease, or bovine spongiform encephalopathy
(BSE) as it is officially called, is an incurable brain-wasting disease
in cows, which Britain first detected in herds in1986. Since then, more
than 100 people in Europe, almost all of them in Britain, have developed
vCJD from eating BSE-infected meat.
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- BSE, vCJD and other related illnesses, such as the animal
disease scrapie, are marked by the build-up in the brain of abnormal versions
of proteins called prions.
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- Although people fall ill after eating infected meat,
in the January issue of the Journal of Virology, Dr. Richard Bessen and
his colleagues report that not all hamsters that consume foods that can
lead to prion disease become sick as a result.
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- However, when the researchers injected the prions into
the tongues of hamsters, they found that all animals became infected with
prions, and did so more quickly than if they had eaten disease-causing
food.
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- "Inoculation into the tongue was more efficient
than ingestion," Bessen told Reuters Health.
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- Bessen and his colleagues also discovered that all hamsters
with a small lesion on their tongues became infected with the disease after
eating infected food. These hamsters became infected more slowly than when
the prions were injected into the tongue, but faster than if they had eaten
the food without a tongue lesion.
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- These findings suggest that cuts in the mouth put eaters
of foods that can cause prion disease more at risk of disease than otherwise,
Bessen noted.
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- The researchers also found that after injecting prions
into the brains of hamsters, prion infection spread to the animals' tongues,
indicating that the tongue can serve as a reservoir for prion disease.
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- In an interview, Bessen explained that prions travel
along nerves, and the tongue is attached to a vast network of nerves. He
noted that prions likely move between the tongue and the brain using that
nerve highway, by traveling along the nerve that enables the brain to control
the movement of the tongue, and the nerves that reach the tastebuds.
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- Bessen said that the next step is to determine whether
the same process occurs in sheep and cows, the animals whose prion diseases
may put humans at risk. In the new study, the researchers used a type of
prion known to cause disease in mink.
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- "Whether (these experiments) have relevance in natural
infections, we really don't know," Bessen said.
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- SOURCE: Journal of Virology 2003;77:583-591.
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