Roger Morris shocked many in a University of Saskatchewan lecture theatre May 13 when he said the prion believed to be responsible for BSE and its human counterpart might be transferred through blood.
Until recently it was believed that bovine spongiform encephalopathy could be practically spread only by eating specified risk materials such as brain, nerve and lymphatic tissues from infected cattle.
Scientists nearly all agree that variant Creutzfeldt-Jakob disease, or vCJD, is how BSE shows up in a human.
Morris said that while infection was possible via blood products, it was far more likely that “you might be hit by a meteorite.
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“This affects so few people or cattle worldwide that the response to the problem has been grotesquely out of proportion to the risk itself.”
Morris is one of the world’s top researchers in their field of prion diseases and molecular neurobiology. The King’s College professor from London, England was in Saskatoon for a forum dealing with BSE and its impact in Canada over the past year.
He said the risk to humans of BSE infection via doctors is far greater than through cows.
“If we are keeping score, which we are, infections by clinicians 312, cows 146.
If we were going to have a cull based on this reality, it wouldn’t necessarily be the cows that needed to go.”
Human error by health-care providers and new approaches to screening for BSE need further research, said Morris.
In Japan, vCJD has been caused by transplanting BSE-infected human tissue during brain surgery. In France, it was caused when “questionably obtained” human growth hormone was injected into children.
Morris said there have been no reported cases of transfer through blood transfusions.
Most western countries prevent blood donations from people who have spent long periods of time in higher risk countries such as the United Kingdom.
Chris Clark teaches at the Western College of Veterinary Medicine in Saskatoon and was studying and practising in the United Kingdom during the height of that outbreak. He said the spread of BSE was caused by human error through adding infected animals’ tissues to feed.
“It was a cheap source of high protein feed. In the U.K. we can’t grow alfalfa and other high protein feeds, so we turned to another source,” he said.
Morris said feeding rendered bovine meat and bone meal to cattle hasn’t been as widespread in North America and bovine feeding bans in 1997 have further restricted the chance of the disease spreading.
“It just isn’t likely the same threat in North America,” he said. “We created the scrapie problem in the U.K., too.”
In the 1930s the British sheep population was inoculated against a disease not related to scrapie, but later it was discovered the inoculant itself was infected with scrapie.
