CWD down in Wisconsin, according to DNR - WQOW TV: Eau Claire, WI NEWS18 News, Weather, and Sports

CWD down in Wisconsin, according to DNR


Madison (AP) - Wisconsin Department of Natural Resources officials say 6 percent of deer tested last year were infected with chronic wasting disease.
According to DNR data presented to the agency's board Wednesday, 593 of 9,685 deer tested between April 1, 2017 and Feb. 10, 2018 tested positive for the disease, a prevalence rate of 6.1 percent. The testing season runs from April through March.

In 2016, 7.3 percent of deer tested positive for the disease in Wisconsin. The 2015 rate was 9.4 percent, the highest since the disease was discovered in Wisconsin in 2002.

The DNR has analyzed 209,615 deer since the disease first appeared in the state, with 4,175 testing positive.

Bryan Richards, Emerging Disease Coordinator for USGS National Wildlife Health Center provided News 18 the following comment on the story.

"The title of the article is more than slightly misleading.

To suggest that somehow CWD is actually "down" in Wisconsin is likely incorrect, and mis-characterizes the data collected by the Wisconsin Department of Natural Resources. 

The term "prevalence" is more than a simple numerator and denominator.

One must consider where deer were sampled, and what deer were sampled, before an assessment can be made about "prevalence."

For instance, if we sampled 100 deer in the Apostle Islands and did not find any CWD, would the statewide prevalence be zero (0/100)?

And if we sampled 100 deer in Iowa County and found 25 positives, could we say that statewide prevalence of CWD is 25%?

Last year the DNR designed much of their surveillance effort to look for disease on the outskirts of where it had previously been found.

So it is reasonable to assume that proportionally you might find fewer positives.

But this does not reflect a statewide average value as the DNR does not have the fiscal capacity to look "statewide" in any one year.

Here's what might be more interesting.

The sate found ~593 positives last year, the most ever found in Wisconsin.

Yes, the total amount of surveillance increased last year, so we have to put the total in perspective.

That's why we need the denominator as well (~10,000 samples).

But we cannot over simplify, and draw conclusions (as your title did).

Nearly 600 positives is a large number, more than ever found in Wisconsin, or any other state in a single year.

CWD is almost certainly not "down in Wisconsin."

People look to the media for accurate information, and when they read headlines, it helps them form opinions.

I suggest it is the responsibility of the media to assure that they are not misleading the public."

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