Scientist says CWD efforts on target

Correspondent

Madison Beth Williams, DVM, Ph.D., from the University of
Wyoming Department of Veterinary Sciences, told a packed auditorium
on the UW-Madison campus that Wisconsin is acting correctly in its
efforts to rid the state of chronic wasting disease (CWD).

“Wisconsin seems to be on the right track, and has been brave in
stepping forward to try to control CWD,” Williams said.

“I am quite supportive of what the Wisconsin DNR is doing, and I
would advise them to keep on doing it. I think it’s important to
the rest of the country that you have the opportunity. It seems
that it is fairly localized here, which is good to know, and if
they don’t do anything, I have no doubt that it will spread and go
other places.

“Their (DNR) approach may not work, but if they don’t try, then
you know that it will be everywhere, so what they’re doing is
important.”

Williams is considered by many to be the primary “U.S. expert”
on transmissible spongiform encephalopathies (TSEs), which includes
CWD. She was the first researcher to describe a “chronic wasting”
syndrome in captive mule deer in Colorado and has now studied CWD
for more than two decades. She served on a panel of experts who
attended two days of meetings in Madison to learn about efforts of
the Wisconsin DNR to rid the state of CWD. She then was the keynote
speaker for the Aldo Leopold Lecture Series in Natural Resources on
April 24, providing a general overview of human and animal
TSEs.

Williams noted that Wisconsin has a strong background in
wildlife disease studies, as Dr. Dan Trainer (then UW-Madison
professor of wildlife diseases who went on to become dean of the
College of Natural Resources at UW-Stevens Point) was the first
editor of the wildlife disease bulletin in the 1970s, and the late
Dr. Richard Marsh of UW-Madison was an earlier researcher of
TSEs.

“Wildlife in general is very healthy (in the state),” she
said.

TSEs are an unusual group of diseases that affect humans and
animals. The diseases are transmissible and affect the central
nervous system.

Several of theses diseases are:

Scrapie which has been known for 300 years and affects sheep and
goats.

Bovine spongiform encephalopathy (BSE) came on the scene in the
1980s in the United Kingdom.

Kuru Affected tribal members in New Guinea who practiced
cannibalism, and the incubation period can be as much as 40
years.

Creutzfeldt-Jakob Disease (CJD) Occurs about one per million in
the human population.

CWD The origins may never be known, and it’s a disease in deer
and elk. There is some evidence that it came from a scrapie
agent.

“We may never know where CWD came from,” Williams said. “There’s
a lot that we don’t know, but we do know it’s a disease of
white-tailed deer, mule deer, and Rocky Mountain elk. There is
question of whether it occurs in red and fallow deer.”

Using unnatural inoculation, it has been shown through
intercerebral inoculation to be transmitted to cattle, sheep,
goats, ferrets, mink and mice. It is not known if oral inoculation
will provide the same transfer.

Williams showed where CWD was in captive animals in Colorado and
Wyoming in 1980, and a few mule deer in the Ontario Zoo. The
distribution hadn’t changed by 1985, but by then it also was seen
in free-ranging deer and elk in Colorado and Wyoming.

By 2000 it also was found in Montana, Nebraska, South Dakota,
and Saskatchewan. By 2003 it was found in Korea, Wisconsin,
Minnesota, Illinois, New Mexico, Kansas and Utah.

“There is a pattern here, and it is not good,” she said. “I
don’t know about the future, but it’s a good bet that it will be
found elsewhere.”

Williams suggested that in some animals that died in earlier
years because of initial symptoms it may have been diagnosed as
aspiration pneumonia instead of CWD.

The standard laboratory technique used to study the brain is
immunohistochemistry. There is no live animal test available yet. A
tonsil biopsy is being used now and is useful for research, but
it’s not considered efficient, and a better technique is
needed.

CWD is found in lymph nodes and the central nervous system, and
recent work has shown that the abnormal protein, when ingested
orally, can be found in the skeletal muscle of mice and hamsters.
Williams said that it has not yet been seen in skeletal muscle of
deer or elk.

Another question is transmission. Scrapie is transmitted through
the placenta, but this has not yet been detected in deer or elk
although placental samples are being tested in Wyoming.

“There is an abundant amount of evidence of horizontal
transmission from animal to animal,” Williams said. “There is
concern over saliva, feces, urine and what role decomposing
carcasses play in spreading CWD. We don’t yet know.

“Transmission and epidemiology of what we see in Colorado may be
different than in Wisconsin,” she said. “It is different habitat
and the densities of mule deer (2 to 5 per square mile) and
white-tailed deer (up to 100 per square mile of habitat) in the two
states are extremely different. We need to have local
information.”

Williams said that environmental contamination plays a role
based on anecdotal information. “Multiple occurrences of animals
coming from areas where CWD does not occur, they move into areas
where animals with CWD were present, and the disease occurs. That
has been anecdotal and we have on-line transmission studies
established that should shed more light on that.”

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