TORONTO — The human food chain may not be as well protected from BSE as everyone hopes, scientists admitted Thursday in the wake of publication of new research showing the malformed proteins that cause the brain-wasting disease can be found in more tissues than previously thought.

Experts admit the findings are worrisome, but note the additional risk, if confirmed, may still be low because it is believed there is very little bovine spongiform encephalopathy -- mad cow disease -- in current cattle herds.

"I don't want to provoke hysteria here,'' senior author Dr. Adriano Aguzzi said in an interview from Zurich, where he is a researcher at the institute of neuropathology at University Hospital.

"The bad news is that the prions are likely to distribute in the body more broadly than we would have thought possible -- and that's obviously bad news.

"But ... the good news is there is very little BSE left in Europe and there has always been very little BSE in North America.''

A prion expert at the University of Toronto said if the findings are confirmed in cows -- the research was done in mice -- current regulations aimed at keeping high-risk meats from entering the food chain will have to be reconsidered.

"The specified risk material ban is to protect us from being exposed to BSE prions. If there's a way for BSE prions to circumvent this barrier to actually propagate in muscle (meat), then we're in trouble again,'' Dr. Neil Cashman said.

"I think it's a clear threat and it deserves ample consideration.''

But the director of animal health laboratory services at the Canadian Food Inspection Agency said it is too soon to conclude the risk of acquiring variant Creutzfeld-Jakob disease -- the human form of BSE -- from eating beef is higher than previously thought.

"Are we concerned about it? Too early to tell,'' Dr. Shane Renwick said.

"We certainly are very interested in it. And I think there'll be a lot of interest around the world in this research. But it is preliminary in nature.''

Renwick defended the current regulations, built around ensuring that tissues considered high risk -- brains and spinal cord, gut and lymphatic tissue -- don't enter the food chain.

"Given what we know I think the firewall is excellent,'' he said from Ottawa.

The research was published online Thursday by the journal Science.

Researchers from Zurich, the Institute of Neurology in London and Yale University School of Medicine set out to see if there was a link between inflammation and prions.

Their theory was that inflammation might provoke migration to and propagation of prions in tissues where they are not normally found. Inflammation would be found in animals sick with viruses or auto-immune conditions.

The scientists injected prions into mice suffering from one of five different conditions causing inflammation in the kidney, pancreas or liver. (Those organs, normally thought to be prion-free, were randomly selected.) They then looked to see if they could detect the misfolded proteins in those organs.

They did, in all of the mice.

"Three organs, five different inflammatory conditions -- this makes a very tight case,'' Aguzzi said.

"I have hardly any doubt that these findings can be extrapolated to additional organs as well.''

Cashman pointed out a caveat, calling it "a ray of hope.'' The prions used in the experiment were the type that cause scrapie, the brain-wasting disease that afflicts sheep.

Scrapie is believed to have jumped the species barrier to cows -- triggering BSE -- but has not been found to be a direct risk to humans.

The scrapie prion and the one that cause BSE don't work exactly the same way, Cashman noted. But it's crucial that additional research is done to see if what happens in mice will also happen in cattle.

"Clearly the experiments have to be done with inflamed bovine muscle,'' he said.

Aguzzi agreed, but said he cannot work with such large animals in the laboratories in Zurich. Instead, his team is testing the thesis in sheep.

"I predict that they (the results) are probably very well extrapolated to sheep,'' he said.

"I don't know how much of this will hold true for the cow and this needs experimentation. It could be either way.''

In the interval, authorities should stringently enforce regulations aimed at ensuring sick cows don't make it into the food chain, Aguzzi said. "If sick cows were reliably not entering the human food chain, then there would be no reason to worry because of our new findings.''