A British health expert has thrown down the gauntlet to the medical establishment, attacking the belief that mad cow disease causes a fatal disorder of the human brain and branding the scare as "the epidemic that never was."
Variant Creutzfeldt-Jakob disease (vCJD) is the name conferred in 1996 to a type of spongiform encephalopathy -- a disease in which a rogue prion protein destroys brain cells, turning the brain progressively spongey.
Scientists considered it to be a new form of a rare condition, Creutzfeldt-Jakob disease, and linked it to the consumption of meat from cows infected with the bovine form of this ailment.
But George Venters, a public health specialist writing in Saturday's issue of the British Medical Journal (BMJ), says the medical profession has been stampeded into adopting this view.
He contends the condition called vCJD is not caused by eating bovine prions -- nor in fact is it new.
"What was initially a speculation has now evolved into orthodoxy among the medical profession in the United Kingdom if not the whole of Europe, although in the United States the question of causality remains more open," says Venters.
Venters, a member of a district health board in Lanarkshire, Scotland, puts forward this argument:
-- There is "no direct evidence" to prove that bovine spongiform encephalopathy (BSE), or mad cow disease, has leapt the species barrier to humans.
Prions produced by grazing animals are different to those in humans. And lab tests have shown that mice genetically engineered to carry the human prion gene cannot be infected with the BSE prion, even if this is injected directly into their brain.
-- For the BSE prion to be transmissible to humans, it would have to overcome an unbelievably tough series of hurdles.
"To be infectious, it would have to survive cooking, digestion and the human immune system ... also, ingestion is an inefficient route of transmission of prions other than by cannibalism."
-- Why, asks Venters, is the estimated number of vCJD victims so low? Normally, the toll from a foodborne disease rises very quickly. But in the case of vCJD, the rise is still very slow.
This, says Venters, suggests that cases that have been diagnosed as vCJD are in fact ordinary CJD, a rare condition first diagnosed in 1913.
In addition, doctors are now alerted to spotting brain disorders because of the scare and cases that previously would have been written off as dementia or senility are now being identified as prion casualties.
"I believe that the evidence now available casts serious doubts on the case for a causal link between bovine spongiform encephalopathy and 'new' variant Creutzfelt-Jakob disease," he says.
"The medical profession should, at least, be publicly debating this as an issue."
Mad cow disease has been one of the biggest and costliest health scares of modern times.
Experts in prion diseases generally concur that vCJD is new and that it is caused by the BSE agent.
They admit, however, that there are many gaps in the knowledge about how and why this prion leaps the species barrier.
Among the biggest unknowns are whether there is a genetic susceptibility to the agent -- whether some people are more vulnerable to it than others -- and how long the disease incubates before the first symptoms appear.
This, they say, explains uncertainty about the progression of the disease, because it is unclear whether the final toll, spread out over decades, will be in the hundreds, thousands or even higher.
The official toll, as of July, stood at 102 people in Britain, the epicentre of the BSE epidemic, plus three in France and one in Ireland, according to Britain's vCJD Surveillance Unit.
Hundreds of thousands of cows have been slaughtered in a bid to end the BSE epidemic, and the cost is estimated in the billions of dollars, in Britain and in continental European countries which imported contaminated British animals or cattle feed. Bureau Report