PINE ISLAND, MINN. - Wednesday morning, a chilled breeze found its way down the main drag of this southeastern Minnesota town. But John Mohlke and his son, Jeff, had been bundled warmly enough while hunting deer that morning, and seemed not to mind the cold as they leaned against a trailer that toted the fruits of their labors: two deer, a doe and a buck.

Longtime hunters, the Mohlkes were participating in a novel autumn undertaking.

Their deer -- killed in a special chronic wasting disease (CWD) zone in southeast Minnesota -- were being cut open with near surgical precision, and a sample of their lymph nodes removed.

The man with the scalpel was DNR wildlife technician Anthony Wolf of Glenwood, Minn.

"Now if you'll show me on the map where you shot your deer," Wolf said, walking to a large diagram of the countryside surrounding Pine Island.

The Mohlkes are two of more than 1,000 hunters who have submitted deer for CWD testing since the state's firearms whitetail season began Saturday. Samples of the animals' extracted lymph nodes have been sent either to the University of Minnesota or a similar laboratory in Colorado for testing.

Results for the 290 deer whose tests have been completed have been negative.

"It's going as well as can be expected," said DNR wildlife research manager Lou Cornicelli, noting the testing effort is time-consuming, manpower-intensive and costly.

Chronic wasting disease became a concern in Minnesota a year ago when a doe killed by an archer not far from Pine Island was found to carry the disease -- the first wild whitetail known to be afflicted in Minnesota.

Previously, CWD in the state had been limited to a relative handful of captive elk, the first in a herd near Aitkin in 2002, and most recently at an elk farm near Pine Island that is now closed.

CWD is an always-fatal brain disease that also afflicts moose. It is not believed to affect humans.

In January, the DNR enlisted hunters in a special deer culling operation in the southeast. The intent was to harvest enough deer for testing to determine if CWD infection was widespread.

In all, about 1,180 deer were killed, many by DNR contract sharpshooters, of which 750 were tested (the rest were fawns, which typically aren't tested). All tests were negative. (Test results and other CWD information are at www.dnr.state.mn.us/cwd.)

Wanting to check still more deer this fall, the DNR established a special hunting zone -- Permit Area 602 -- in the southeast in which licensed hunters can purchase nominally priced permits to kill as many deer as they want (only one buck; typical hunting regulations apply).

The idea, said Cornicelli, is again to determine whether CWD exists in the region's wild whitetails, and if so, how widespread it is.

"We want to check as many deer as possible," he said. "We set a target of 600 for the [special permit area], but maybe it'll be 800 or so."

Five DNR registration stations are located in area 602. Surrounding it are another 21 DNR sampling stations, all of which also extract lymph nodes of harvested deer for testing.

Special restrictions this year require hunters who kill deer in 602 to keep their carcasses in the area until negative test results for their animals are returned via the DNR website.

"Some hunters had to wait in line last weekend because so many deer were brought in, but hunter cooperation has been incredible," said CWD surveillance coordinator Dave Pauly of the DNR.

A few animals brought to sampling stations since the opener have been trophies that hunters intended to mount, Pauly said. Before lymph node samples were collected from them, taxidermists were allowed to remove their hides, or "cape" them.

Lymph node samples from animals killed in 602 so far have been sent to the U, with results returned in about three days. Testing of deer harvested just outside that zone is being done in Colorado, with a result turnaround time about twice as long.

On Wednesday, John and Jeff Mohlke waited patiently while Wolf, the DNR wildlife technician, leaned over their deer with a scalpel in hand, performing his precision handiwork.

Pleased that they had bagged a couple of deer, they nonetheless were concerned that the culling operation last winter, combined with the area's liberal hunting regulations this fall, might result in too many whitetails being killed, depleting the herd.

Cornicelli doesn't expect a long-term deer population problem.

"Assuming we don't find more CWD in the area, any deer reductions will be temporary," he said.

Dennis Anderson • danderson@startribune.com