Field Note - Searching for CWD

Two and a half years of surveillance and the intensive effort to test about 4,400 deer harvested during the past firearms hunting season failed to turn up any sign of chronic wasting disease, but DNR wildlife research manager Mike DonCarlos isn’t breathing a sigh of relief. Hunters voluntarily allowed DNR staff to remove the heads of harvested deer in 17 antlerless permit areas, where about 10 percent of the wild deer in Minnesota reside. The search for chronic wasting disease, or CWD, in Minnesota’s wild deer herd, he said, has just begun.

This year testing will be done until samples have been taken from wild deer in all of the state’s 130 permit areas. Samples of deer lymph nodes will be extracted from the heads and tested at the University of Minnesota. Hunters who volunteer their deer for testing will be notified individually of the results by mail.

With a few changes to increase the efficiency of the process, DonCarlos said that within three years DNR staff hope to collect the 30,000 samples necessary to assess the likelihood that CWD exists in Minnesota’s wild deer herd.

If CWD is discovered in Minnesota’s wild deer, DNR staff will work aggressively to contain the disease by culling wild deer using special hunts, DonCarlos said.

The inevitably fatal disease attacks brain tissues in deer and elk, causing lethargy, disorientation, and emaciation. CWD is similar to mad cow disease in cattle and Creutzfeldt-Jakob disease in humans. Researchers suspect deer and elk pass the infection from animal to animal, but they don’t know how.

So far, CWD in Minnesota has been limited to farmed elk. One elk tested positive for CWD after it died on an Aitkin County farm in August 2002. A second elk, which was part of a herd exposed to the Aitkin elk, tested positive after it was quarantined and killed for testing on a Stearns County farm in January 2003.

Just as important as finding out whether the disease is present in Minnesota’s wild deer is preventing it from entering Minnesota, said DonCarlos. At the urging of the DNR, Board of Animal Health, and Department of Agriculture, the state Legislature has passed laws aimed at keeping CWD out of the state.

Beginning this fall hunters will no longer be allowed to bring whole elk and deer carcasses from other states into Minnesota. However, hunters will be allowed to bring meat, hides, and antlers with clean skull plates. The restrictions will help keep CWD-infected spinal and brain tissues out of the state.

Currently, the DNR is responsible for regulating certain deer and elk farms. In January 2004 all regulatory authority for deer and elk farms will be transferred to the Board of Animal Health. Deer and elk farmers will be required to submit for CWD testing any captive deer or elk that is slaughtered or dies if it is older than 16 months. Farmers will also be required to keep records of sales and transfers of deer and elk.

Despite the intensive testing and new legislation, DonCarlos remains concerned.

"The risk factors are all still there," he said. "So far the news has been good, but we’ve still got roughly 90 percent of the wild deer herd to test in the next two to three years."

And even if the disease isn’t found in the next few years, DonCarlos noted that’s not definitive.

"Testing is time sensitive," he said. "Right now CWD could be moving into a permit area we sampled during last fall’s hunting season. Monitoring and following up on reports of deer that show symptoms of CWD will continue to be a priority for a long time."

Meanwhile, hunters are encouraged to wear gloves when field dressing deer and avoid eating brains, spinal tissue, and lymph nodes of deer, DonCarlos said.

Jason Abraham