Bad News on Mad Deer Disease

Diseased deer may pose risk to humans

Experts investigate link between infected venison and deadly brain illness

of the Wisconsin Journal Sentinel staff

April 28, 2002

Six years ago, D. Kevin Boss died of a rare disease, a degenerative disorder
that seemed to dewire the brain of the computer engineer, circuit by

Chronic Wasting Disease

Part 1: Deer strategy a guessing game (4/27/02)

The death of the former Minneapolis resident from Creutzfeldt-Jakob disease
(CJD) otherwise might be unremarkable except for this: Boss got the disease
at an unusually young age, 39, and he regularly consumed venison, including
deer meat from Wisconsin.

Last month, chronic wasting disease, an always-fatal brain disorder that
affects deer, elk and other cervids, was found in the Wisconsin deer herd.
The disease is similar to Creutzfeldt-Jakob disease, an always-fatal brain
disorder that affects several hundred people in the U.S. every year.

No one is saying that Boss got Creutzfeldt-Jakob disease from eating
infected venison. In fact, such a case has never been established in medical

But the emergence of chronic wasting disease in deer in Wisconsin and other
states has raised questions about whether eating meat from infected deer can
cause deadly brain illness in people.

It's an area that scientists now are actively investigating.

Already, several red flags have been raised.

A variant form of Creutzfeldt-Jakob disease has been linked to the
large-scale outbreak of bovine spongiform encephalopathy (BSE), also
known as mad cow disease, in cattle herds in Europe.

Bovine spongiform encephalopathy has been tied to the deaths of more than
100 people since 1995. It is believed that those people became ill after
eating beef from infected cattle.

Could a similar story be unfolding with deer meat and people?

"We really don't know," said Piero Antuono, a professor of neurology at the
Medical College of Wisconsin who has autopsied the brains of
Creutzfeldt-Jakob disease patients. "You wonder if there is a connection.
"This is very reminiscent of the BSE story in England in 1986 and '87 when
we didn't know."

In October 2001, a study in the journal Archives of Neurology reported on
the cases of three relatively young individuals who contracted CJD and who
also had been deer hunters or had regularly eaten venison.

The three individuals, who were from Maine, Oklahoma and Utah, all were
under the age of 30 and came down with the disease between 1997 and 2000.
The vast majority of CJD patients get the disease in their 60s and 70s.

The researchers, who included scientists from the U.S. Centers for Disease
Control and Prevention, concluded that although the circumstances suggested
a connection with chronic wasting disease, they could find "no strong
evidence of a causal link."

Such statements are far less emphatic than those made by British officials,
who in the mid-1990s tried to assure the public about the safety of beef by
having their children eat hamburgers in front of television cameras.

In 1995, then-Prime Minister John Major categorically stated that "humans
don't get mad cow disease," only to have his health secretary announce a
year later that BSE was spreading from cows to people.

In the U.S., no one is saying that chronic wasting disease can't jump from
deer to people.

They point out that the overall incidence of Creutzfeldt-Jakob in the U.S.
is about one in a million.

The annual incidence among people under age 30 is about 5 per billion, said
Lawrence Schonberger, a medical epidemiologist with the Centers for Disease
Control and Prevention. However, if you eliminate cases involving infections
caused in medical settings, such as cornea transplants and injections of
growth hormones obtained from cadavers, that rate drops to roughly 1 per
billion, Schonberger said.

In fact, only four such cases were found in the U.S. between 1979 and 1996.

So three cases of young hunters in just four years is cause for concern.

"There isn't any hard data, but what data there is suggests that humans may
be vulnerable," said Michael Hansen, a biologist and senior research
scientist with the Consumers Union, which publishes Consumer Reports.

The Union has been pushing the federal government to do more to prevent mad
cow disease from entering the U.S. and to limit the spread of other
so-called transmissible spongiform encephalopathies, or TSEs, such as
chronic wasting disease.

For instance, the Union says stricter rules are needed to ban the feeding of
meat from deer and elk possibly infected with chronic wasting disease to
other animals such as hogs, poultry and pets. That's because another big
fear is that chronic wasting disease may someday jump from deer to another
species such as cattle.

In a dairy state such as Wisconsin, that concern is especially relevant.

So far, no such cases have been found.

However, laboratory research suggests that it is possible.

TSE diseases such as chronic wasting are believed to be caused by prions,
mutant proteins that have the ability to cause normal proteins to mimic
their distorted shape, resulting in a buildup of sponge-like holes in the

Prions are particularly adept at infecting nerve cells such as those found
in the brain, spinal cord and eyes.

One reason prions are so feared as infectious agents is that they are highly
resistant to heat and other sanitizing methods. It is believed that they can
exist in the soil and other locations for years and resurface to infect

Two years ago, Byron Caughey and other researchers at the Rocky Mountain
Laboratories in Hamilton, Mont., analyzed prions from deer infected with
chronic wasting disease.

If lab tests can be both reassuring and chilling, that's what Caughey, a
National Institutes of Health researcher, found.

The analysis showed there was a substantial molecular barrier that helped
prevent chronic wasting prions from converting normal human protein to the
mutant form. However, despite the barrier, the deer prions ultimately were
able to convert human protein to the mutant form.

And it did so with about the same level of efficiency as mad cow prions.

"It is low efficiency . . . but it can happen," Caughey said.

Caughey, who obtained his doctorate from the University of
Wisconsin-Madison, also found that mad deer prions converted cattle protein
to the mutant form at a slightly higher efficiency than it converted human
protein, suggesting that cattle might be more vulnerable than people.

Jim Kazmierczak, an epidemiologist with the Wisconsin Division of Public
Health, said that while Caughey's research raises concern, it was done under
laboratory conditions that may or may not accurately mimic what occurs in

"I'm not saying it doesn't mean anything," he said. "To me it's not terribly

He noted that Creutzfeldt-Jakob disease has been around a long time, and the
incidence has not changed much. It is still a very rare disease, with only
about five new cases a year in Wisconsin.

However, he added, "We just can't reassure people the risk is zero."

State health officials now are on the lookout for suspicious
Creutzfeldt-Jakob cases and have asked hospitals to report any such patients
under the age of 55.

Several ways to infect

Another disturbing bit of science was presented in March by Stanley B.
Prusiner, the University of California at San Francisco researcher who won a
Nobel Prize for his study of prions.

Prusiner found that prions linked to mad cow disease were found in the
muscles of mice that were experimentally inoculated, suggesting that the
mutant agents can exist not just in nerve tissue, but also in meats.

The researchers noted that the pooling of prions in the muscles may vary
from species to species. Although disconcerting, the researchers said that
does not prove that eating muscle meat from infected cattle causes disease.

The study did not involve prions from infected deer.

However, the report and comments from health officials suggest that there
may be several ways that deer prions could infect people.

A bullet fragment could travel through prion-infected nerve tissue and into
muscle tissue.

Another possibility is in the processing of meat from diseased deer. Saws
and butchering equipment could cut through diseased nerve tissue and then
into meat.

Complicating matters further, butcher shop hygiene is a far cry from the
strict hospital standards required when invasive procedures are done on CJD

Prions from CJD are so infectious that rigorous rules are followed when
doing autopsies on the brains of CJD patients.

A 1999 World Health Organization report also noted that there have been
several cases of people being infected after coming into contact with
contaminated neurosurgical instruments. Cornea transplants also have
infected people.

For surgical and other invasive procedures, "Persons with confirmed or
suspected TSEs are the highest-risk patients," the report warned. "They must
be managed with specific precautions."

Lab work needed

As far back as 1986, studies had suggested a possible link between exposure
to deer and the risk of Creutzfeldt-Jakob disease.

That year, a small study involving 26 CJD patients by researchers at Temple
University and the National Institutes of Health found that exposure to deer
through a hobby such as hunting resulted in up to a ninefold increased risk
for the disease.

Chronic wasting disease was first recognized by biologists in Colorado deer
during the 1960s.

Ultimately, establishing a strong link between chronic wasting disease and
CJD will take extensive lab work.

Such work now is going on at the National Prion Disease Pathology
Surveillance Center at Case Western Reserve University in Cleveland.

For several months, researchers there have been looking for molecular
similarity between infected deer prions and prions from people who have died
from CJD.

It probably will be a couple months before any results are known, said Shu
Chen, an assistant professor of pathology at the university.

In the meantime, deer hunters and widows of CJD patients can only wonder.

Linda Boss Price, whose husband, D. Kevin Boss, died of CJD in 1996, said it
never occurred to her that there might be a connection to chronic wasting
until the disease was found in the Wisconsin deer herd last month.

She said her brother hunted deer in Minnesota and Wisconsin, mainly in
Barron County, and often supplied the couple with deer meat. Her husband was
a bird hunter and often returned the favor by giving his brother-in-law

The couple regularly ate venison in the form of steaks, chops and sausage.

Then, in 1994 he started having problems.

First he had trouble using his computer keyboard. He lost verbal skills. He
couldn't feed himself. He would walk outside in the winter without pants on.

"It was like a real fast Alzheimer's," said Boss Price, who has since
remarried. "It was like his brain was disconnecting."

Eventually, he had problems swallowing and breathing. He died in a nursing
home two years after the first symptoms appeared. He was 41.

She said she has no clue how her husband got sick or whether it was related
to chronic wasting disease.

But, she said, "He was far too young for it."

Appeared in the Milwaukee Journal Sentinel on April 29, 2002.

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