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7-02-2002
Interesting story about research being conducted and planned at the NIH lab in Hamilton, Montana (and some of you thought Montana was a remote isolated location). Note the work done on hamster to mice, another example of interspecies transmission which apparently has a "skip generation" component to it.
Thomas J. Roffe, PhD, DVM
USGS-BRD
Northern Rocky Mountain Science Center
FWP Bldg, 1400 S. 19th Ave.
Bozeman, MT 59718-5496
T: 406-994-5789
F: 406-994-4090
Cell: 406-539-4955
Supporting Documents:
Primate studies to focus on CWD
Researchers trying to find out if humans can catch disease plaguing deer,
elk populations
By Lou Kilzer, News Staff Writer, Rocky Mountain News
June 29, 2002
The race is on to find out whether a fatal brain disease in
deer and elk poses a risk to human venison eaters.
"That's what everybody is trying to find out,"
said Dr. Pierluigi Gambetti, head of a national team studying the occurrence of
the deadly protein disease.
Perhaps most significantly, a National Institutes of Health
laboratory in Montana is planning to experiment with primates to try to
determine human susceptibility to chronic wasting disease.
"Primate research is the most direct way to find out if
people are susceptible," said NIH research scientist Richard Race.
"It's the species that's most closely related from an evolutionary point of
view to people. You cannot inoculate humans on purpose, so the next best thing
is some kind of a non-human primate."
But even with the groundbreaking research, Race said,
answers are unlikely to come anytime soon. The process could take years, he
said. Meanwhile, Gambetti's group and others are gearing up for studies of
genetically manipulated mice to see if they can be infected with chronic wasting
disease.
"We don't know whether it can be transmitted to humans
and if it is transmitted, what it's going to look like," said Gambetti.
There are no proven cases of CWD infecting humans, but
concern has intensified as the disease has spread from its endemic areas in
Colorado and Wyoming to several other states and two Canadian provinces.
There have been several cases reported in which human
venison eaters have contracted Creutzfeldt-Jakob disease (CJD), which, like CWD,
is a transmissible spongiform encephalopathy (TSE), but one that occurs
naturally in humans.
Gambetti said that these cases seem to fit into known
subtypes of CJD, but he added that the assumption that human cases from deer or
elk would look different upon microscopic examination than ordinary CJD is just
that -- an assumption.
Most scientists believe all TSEs -- CWD, CJD and mad cow
disease in cattle -- are all caused by a mutant protein called a prion.
Most scientists believe there is a strong barrier preventing prions from one
species from infecting another. But 131 European human eaters of beef have
contracted a variant of CJD caused by eating cattle suffering from mad cow
disease, or bovine spongiform encephalopathy (BSE).
That has sparked concern that other spongiform
encephalopathies, including CWD, could jump to humans or livestock. Some
mice experiments already under way have not detected human susceptibility, said
Patrick Bosque, a Denver neurologist who conducted some of the research in the
San Francisco laboratory of Nobel laureate Stanley Prusiner.
Bosque said those mice have been manipulated to contain a
human gene that produces human protein. After inoculation with CWD, the protein
has not changed to the deadly mutant prion form after more than 600 days.
However, Bosque said the mice model in the experiment might
be flawed. A control group of mice was simultaneously injected with mad cow
prions directly into their brains. Those mice also did not show susceptibility,
even though it is known that humans are in fact vulnerable to mad cow.
That raises red flags about the findings, Bosque said.
More studies with more mice are necessary, most agree.
"Not many people have done much study on a molecular
basis in terms of what the migration pattern would be," if CWD crossed to
humans, said Dr. Shu Chen, the protein expert at Gambetti's lab, the National
Prion Disease Pathology Surveillance Center.
Of human susceptibility, Chen echoed a familiar refrain in
prion research: "The problem is that nobody knows."
Using primates to search for answers is a costly and
potentially controversial step, acknowledged Bruce Chesebro, head of the
laboratory of persistent viral diseases at the NIH facility that will conduct
the research.
Race, the chief scientist involved, knows the pitfalls.
"No matter what the outcome, there are going to be people who fault how it
was done," he said. "One of the reservations we have is that there are
no right answers. Whatever you give the primates some people are going to say
you gave them too much. Some people will say you didn't give them enough."
And there's a political aspect, as well, Race acknowledged.
"If word gets out that it's actually being done, you get all the animal
protest groups and people like that bugging you all the time," he said.
"One thing about it if we do it here (at the lab in Hamilton, Mont.) is
that security is really tight."
Race is the lead researcher on a continuing mice experiment
that has shaken the prion field. In it, hamster prions were injected into
mice, which then showed no outward or microscopic sign of the disease. However,
when brain matter from those mice is injected into another set of mice and
hamsters, they become sick from mutant prions and die.
No one knows how these "sleeper carriers" stay
healthy, or why subsequent test animals become sick. But it raises the concern
that if CWD infected other animals, it is possible that at least the first
generation of the infected species might not get sick.
"It used to be thought the hamster (prion disease)
didn't go into mice. There was a species barrier," said Anne Raines, a
fellow scientist at Rocky Mountain Laboratory. "And now we have some of
those mice going down in a short amount of time; 100 days or so."
"It's such a cool study," said Raines. "Most
people wouldn't do it, because if you're a post-doc or a young investigator it's
really hard to take three or four years to get results," she said, noting
that Race is nearing retirement.
"But (Race) is the sort of person that can dork around
and do something like this and not be under pressure. We're up to fourth or
fifth pass on these guys (mice) now. It's really interesting what we're finding.
It (the prion disease) appears to be possibly sorting out into different
strains."
Race said that while he might begin the primate research, he
would leave it to others to finish it. "There will be somebody here
to see it through," Race said.
Contact Lou Kilzer at (303) 892-2644 or kilzerl@RockyMountainNews.com.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://biology.usgs.gov/cro/CWD7-02-02.htm
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