May 2, 2002 United Press International by Arcella S. KreiterThe death of a Minnesota man from the brain-wasting Creutzfeld-Jakob disease merits further study to determine whether the devastating ailment was a result of consumption of deer meat from animals suffering from chronic wasting disease, a Johns Hopkins University neurologist says.
CWD is a member of a group of diseases -- transmissible spongiform encephalopathies -- that includes mad cow and scrapie. The ailments eat holes in the brain, leaving it spongy. All forms of the disease are fatal and so far have defied scientific efforts to determine exactly how they are spread. Dr. Richard Johnson, in a telephone interview with United Press International, said he is disturbed by recent news CWD has spread from eastern Colorado, across the Continental Divide and into Wisconsin.
"CWD is all the way into Wisconsin. It's been found in white tail deer, not just mule deer. It's crossed the Continental Divide -- I think those are really very significant changes," he said. "What does it mean to human disease? We have no idea. But with that much movement, we want to know if it's a threat."
What has researchers scrambling now is the question of whether D. Kevin Boss of Minneapolis, who died six years ago, contracted CJD from eating venison from Wisconsin deer.
"The very fact that he contracted CJD when he was young (39) -- it's worth looking at," Johnson said, at the same time emphasizing there is no evidence as yet of chronic wasting disease producing CJD in humans.
A study last October in the Archives of Neurology involved three cases of deer hunters under the age of 30 who contracted CJD. They were from Maine, Oklahoma and Utah and contracted the ailment between 1997 and 2000.
Diseases don't easily cross between species, making mad cow, or bovine spongiform encephalopathy, among the few exceptions. More than 100 people in Britain and a handful elsewhere have come down with what is referred to as variant-CJD, which they are believed to have contracted by eating meat from infected cattle. Variant-CJD differs from CJD in that its victims are younger, the progression of the disease is faster and the victims suffer pain.
Laboratory tests conducted by Byron Caughey and other researchers at the Rocky Mountain Laboratories in Hamilton, Mont., found there is a substantial molecular barrier preventing CWD prions from making normal human protein mutate but they eventually were able to accomplish the just that -- at about the same efficiency as mad cow prions.
"It's a low efficiency ... but it can happen," Caughey told the Milwaukee Journal Sentinel.
His research also indicated the CWD prions could convert cattle protein at a slightly more efficient rate.
There are no known incidents of people developing CJD from eating sheep infected with scrapie.
"In Australia and New Zealand, there is no scrapie," Johnson said. "The incidence of CJD of 1 per million per year is the same as elsewhere. ... All of us who eat meat have been exposed to scrapie. I'm sure we've all had mutton from animals that had scrapie."
Johnson also noted there have been cases of vegetarians developing CJD.
Like other TSE, CJD is believed caused by prions, a microscopic protein particle similar to a virus, but lacking nucleic acid, that cause other pieces of genetic material to misbehave.
Dr. Shu Chen, head of prion protein analysis at the National Prion Disease Pathology Surveillance Center at Case Western Reserve University, said research to determine whether CWD triggers CJD is incomplete.
In victims of conventional CJD, the damaging protein deposits are spread throughout the brain tissue while those suffering from vCJD exhibited damage that looked like a daisy, with a core in the middle and damage spreading from there.
"Our impression is these people (the hunters) have typical CJD although we do not know what kind of pathology would be seen if CWD ever passed to man," Chen said. "Looking at the pathology of these people, it doesn't give us some kind of warning sign. The issue has not been solved whether CJD was transmitted through CWD."
Unlike other infectious agents, prions cannot be killed with heat, ionization or radiation.
"Clorox works," Johnson offered. "Things we're used to thinking of as cleaning infectious agents don't (work on prions). Solvents work."
Johnson said the current theory holds vCJD is triggered by consumption of the brains or spinal cords from cattle suffering from mad cow. These "boneless" meats generally were ground up in sausage and hamburger.
"But nobody knows for sure," Johnson cautioned.
Currently, the only way to test animals for TSE is after death. A Swiss company announced this week it has started a joint development with Hadassah University Medical Centre in Jerusalem to create a live test for prion diseases, based on recent findings the disease is associated with a prion protein that shows up in urine.
The U.S. government has imposed strict measures to prevent mad cow from entering the United States, including forbidding the feeding of bone meal to cattle and other ruminants. Last year, two flocks of sheep were seized from Vermont farms because it was suspected some of the animals may have carried mad cow. The animals were slaughtered and tested but it may be another year before scientists can determine which TSE infected the flocks.
In Illinois and Missouri, agriculture officials are taking no chances with CWD either. The states have banned the importation of elk and ordered surveillance of both wild and captive herds already in the states.
"We don't have it, we don't want it and we think we can keep it out," Missouri Agriculture Director Lowell Mohler told the Kansas City (Mo.) Star.
CWD was first recognized in Colorado in the 1970s and there were indications as far back as 1986 that deer hunters had a higher risk of developing CJD than the general population. Spread of the disease in the wild was slow but with the advent of commercial game farms, infection rates have increased.
The Wisconsin Department of Natural Resources Wednesday ordered as many as 15,000 deer will have to be killed in a 287-square-mile area near Mount Horeb to prevent CWD from spreading throughout the state. Elsewhere, the herd will be cut to as few as 10 animals per square mile.
CWD was first detected in November in Wisconsin and since then 516 animals have been tested. Eleven were found positive for the infection.