Faster CWD test selected to screen deer tissue samples

by Rachel Patzer

News Reporter

A new and rapid test responsible for testing deer-tissue samples for Chronic Wasting Disease will soon replace the time-consuming test the Wisconsin Veterinary Diagnostic Laboratory has been using since CWD was first found in Wisconsin in February 2002.

The new test, made by IDEXX, Inc., was selected from five other competing tests as the fastest, cheapest and most precise test for sampling the frozen-tissue specimens of deer for CWD-positive tissues.

There were a number of companies working on simpler diagnostic tests to improve the one used last year. The previous test, known as Immunohistochemistry (IHC), is extremely accurate with almost zero false positives for CWD, but the test requires a fair amount of process time, said Bob Manwell, Public Affairs Manager of the Wisconsin Department of Natural Resources.

The Veterinary Diagnostic Laboratory decided to perform a side-by-side comparison of competing tests to look for the best test to use for this year’s hunting season.

“There is a big advantage to this test. We are strictly focused on the job ahead of us, and the job will be completed in roughly half the time,” said Robert Schull, the Veterinary Diagnostic Lab Director.

The target date for completion of this year’s tests is Jan. 31, whereas the testing went well into April with the IHC test last year, Schull said.

The DNR, the agency responsible for the management plan to combat CWD, is the biggest client for the new test.

With the aid of veterinarians, wildlife biologists, medical scientists and other experts across the country, the DNR has devised a plan for a drastic herd reduction in the area of CWD infection.

“There is no vaccine or treatment for CWD, so according to medical-science expertise, the only practical way to address this health problem is to reduce the population of the deer,” Manwell said.

Because 97 percent of the infected land is privately owned, there has been a significant amount of input from citizens who are directly affected by the reduction plan. A number of town meetings held in the area provided the DNR with the idea of a cash reward for harvesting the deer.

The DNR recently announced a CWD reward program to provide an incentive for individuals to remove CWD-positive deer from the land. Funding of $250,000 is available from DNR funds and private donations, and a reward of $400 will be given for each CWD-positive deer. Much help is needed to aid in the testing process for about 20,000 deer, officials said.

“Shooting this many deer goes way beyond tradition and recreation. It’s a job and not necessarily a pleasant one,” said Manwell.

The Veterinary Diagnostic Lab also performs the CWD tissue test for private citizens who hunt deer. Veterinarians throughout the state will collect the tissue. The lab will use the IHC method for these tissues because of the difficulty in shipping frozen tissue samples.

Although the IDEXX test has not yet been approved by the U.S. Department of Agriculture, the agency who oversees the testing, the test will most likely be authorized by Nov. 1, Manwell said. This leaves plenty of time for testing during the busiest part of the season for hunting.