Paul A. Smith
Tom Carlson, a biologist with the Department of Natural Resources, holds a lymph node taken from a deer at a chronic wasting disease check station in 2013.
By Paul A. Smith of the Journal Sentinel July 22, 2015
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The 2002 discovery of chronic wasting disease in wild white-tailed deer near Mt. Horeb was a watershed event in Wisconsin wildlife history.
Tom Heberlein, a sociologist at the University of Wisconsin-Madison, referred to it as "Fire in the Sistine Chapel."
The finding led to an upheaval in deer management, with an initial goal to drastically reduce deer numbers in the endemic area in an effort to eradicate the disease.
Chronic wasting disease, a contagious, fatal disease to deer and elk known as a transmissible spongiform encephalopathy, also caused concern for the future of the state's deer herd, the foundation of a $1 billion annual impact to Wisconsin's economy.
Since CWD was in the same family as mad cow disease and Creutzfeldt-Jakob (both of which are fatal to humans), it also led to questions about the disease's impact on human health.
Was it safe, for example, to consume CWD-positive deer?
Over the last 13 years, scientists have found no evidence that CWD has caused illness in a human. The abnormal prion that causes CWD has not been shown to cross the species barrier, according to multiple studies.
However, researchers from Case Western Reserve University presented results at a prion conference in late May that are likely to ratchet up concerns over human illness and CWD.
The study, which used humanized transgenic mice, found signs of CWD infection in a small percentage of the test animals.
"These results indicate that the CWD prion has the potential to infect human (central nervous system) and peripheral lymphoid tissues and that there might be asymptomatic human carriers of CWD infection," the researchers summarized.
A peer-reviewed paper of the findings is expected to be published later this year, perhaps as early as next month.
To be clear, there is still no known case of CWD in a human. But the U.S. Centers for Disease Control has long issued strong advice against eating venison from CWD-positive animals.
And since 2003, the Wisconsin Division of Public Health has recommended "venison from deer harvested inside the CWD Management Zone not be consumed or distributed to others until CWD test results on the sources deer are known to be negative."
The Wisconsin guideline says venison from multiple deer should be kept separate and labeled before freezing so any meat from a CWD-positive animal can be discarded.
"Some might call the recommendation overly cautious," said James Kazmierczak, state public health veterinarian for the Wisconsin Division of Public Health. "But the CWD prion has been found in muscle tissue. So from a public health perspective, the safest path is to test your deer and not consume meat from a CWD-positive animal."
Only a small fraction of the state's 600,000 hunters are heeding this advice, however.
If all deer killed last year in the state's 35 CWD-affected counties had been tested, the number would have exceeded 160,000.
But only 5,412 deer were tested last year in Wisconsin. For the record, 327 (or 6%) were positive.
And to be realistic, the state isn't prepared for a crush of deer for testing.
For 2015, the Department of Natural Resources plans to test 4,000 deer for CWD, according to wildlife health section chief Tami Ryan.
The test costs about $90 for each deer; the DNR has budgeted $320,000 for CWD testing this year. The funding will come from a combination of Federal Aid in Wildlife Restoration funds (also known as Pittman-Robertson) and $5 from each antlerless deer tag sold in CWD-affected counties, Ryan said.
The cost and logistics would be daunting for testing even 10 times more deer than were screened for CWD in 2014. Since the disease was discovered in Wisconsin, the most deer tested in a single year was 40,117 in 2002, according to DNR records.
Several sources of federal funding that helped to pay the cost in the early years of Wisconsin's plunge into CWD management are no longer available.
My hunting companions span the range of concern about CWD to confident it's identical to scrapie in sheep (not shown to cause a human illness in more than 200 years) to convinced it's an animal rights group plot to end hunting.
I've had most deer I've shot in the last 10 years tested for CWD. The information (all were negative) put my mind at ease for eating the meat as well as provided landowners with a valuable data point on the health of the local herd.
But I'm in the minority.
"The decision to test is personal," Ryan said. "And the level of concern resonates differently across the state."
Ryan said the DNR plans to do increased surveillance in two areas of the state this year, as well as again work with taxidermists to obtain samples.
In addition, the DNR plans to continue its policy of providing CWD testing at the request of hunters anywhere in the state; contact a local DNR office for details.
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