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
"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.