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    Mad Cow Disease May Be Transmitted Before Symptoms Appear



    The authors calculate that, based on when sheep ate the contaminated cattle tissue, the sheep must have been able to pass on the disease before it started showing symptoms -- something that has been suspected but never before proven.


    Bostock says he does not believe additional precautions need to be taken to safeguard the blood supply as a result of his findings. But he says they confirm the earlier measures, including the ban on U.S. blood donations from certain people.


    Paul Brown, PhD, of the laboratory of Central Nervous System Studies, under the National Institutes of Health, tells WebMD he does not think these early results from the British research should have been published. He wrote a commentary accompanying the research paper.


    "It doesn't change our fundamental way of thinking about this disease," Brown says. "Transfusion has been used for transmission and we know that the blood is infectious. It doesn't change a thing" in terms of the precautions required for blood donations.


    For him, the study's message is limited to its finding that mad cow disease can be transmitted during the disease's incubation period in an "experimental model" involving a blood transfusion from one sheep to another. This does not imply that a sheep could give the disease to a lamb, or that one sheep could naturally transmit it to another even though it shows no symptoms, Brown says.


    Bostock tells WebMD that he wanted to publish his early results because he believed they were in the public interest.


    "The fact is, this experiment in its entirety would take 10 years to complete," Bostock says. "If we were to keep the work secret, that we had a positive transmission, we would be in an extremely uncomfortable position.


    "We are also investigating whether [mad cow disease] can be transmitted between individuals -- either mother to lamb or sheep to sheep," Bostock adds.


    Roger Dodd, PhD, head of transmissible research at the Jerome Holland Laboratory in Rockville, Md. -- the primary research facility for the American Red Cross -- tells WebMD that the researchers' finding confirms expectations. The fact that the sheep developed mad cow disease during the disease's incubation period was the reason "precautions were put in place" for blood donations, he notes.

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