All it took was one sick doe.

The Michigan Department of Natural Resources had watched in recent years as instances of chronic wasting disease, or CWD, had appeared in surrounding states. As far back as 2002, the DNR and the Michigan Department of Agriculture had plans to attack the disease swiftly if it popped up in the Wolverine State.

It happened at the end of August this year when a single whitetail in a Kent County breeding facility was diagnosed with CWD.

Within days, the state had moved to "depopulate"  slaughter  the other deer at the facility, and temporarily ban baiting and feeding of deer throughout the state's Lower Peninsula.

On Thursday, when a judge rejected a challenge to the baiting and feeding ban, the DNR extended it indefinitely.

DNR commission chair Keith Charters said after that vote: "The disease is horrendous. We have to take draconian measures."

Farmers expecting to sell sugar beets, apples and corn as deer feed "have been impacted pretty heavily in a negative economic way," said Rebecca Park, the associate legislative counsel for the Michigan Farm Bureau. "We hear from those members, but we hear from our other members as well who say this is just the right thing to do."

Barely a month before firearms season begins in Michigan  one of the most deer-obsessed states in the country  the state hasn't turned up any more cases of CWD, even after testing (which requires killing) the other penned deer and more than 500 wild ones.

The DNR also ordered mandatory deer checks in a surveillance zone around Kent County, which contains the city of Grand Rapids. It also locked down the entire deer-farming industry until it can complete tracebacks on all animal purchases and sales that may have cross-contaminated deer. Further, it's now illegal to possess any wild deer.

The response has been swift and direct, because when the disease reaches the wild, it's not likely to be eradicated.

"Our history of successful management of chronic wasting disease in free-ranging deer populations is very short," said Bryan Richards, the CWD project leader for the U.S. Geological Survey's National Wildlife Health Center. "Once CWD gets established in a free-ranging population, it's probably there forever. I don't want to say it's impossible, but let's say nobody has done it yet, and it would be extremely expensive, time-consuming and difficult to pull off."

First fully identified in Wyoming in the late 1970s, CWD is a transmissible spongiform encephalopathy, meaning it, like Mad Cow Disease (bovine spongiform encephalopathy), attacks the central nervous system. It's caused by prions  malformed proteins, essentially  that spread through deer-to-deer contact.

No research has yet tied CWD to any disease in humans.

But the disease has been confirmed in elk and moose, and is debilitating in deer. After an incubation period of perhaps 18 months to five years, it will reach a clinical level in which an animal is in obvious distress: emaciated, staggering, drinking large amounts of water, slobbering. Death soon follows.

The prions are durable buggers. Soil taken from pens has been shown to be able to transmit the disease to other deer even years after its last contact with infected animals. A late-stage CWD-infected deer drooling on a baitpile is likely to render the food "hot," or potentially infectious to other deer.

"Getting rid of these things that artificially congregate animals to the same space seems like a reasonable action," Richards said.

A state seeing CWD gain a toehold in its wild population is in for grim and costly work to control it. Take the province of Alberta. It knew it was at risk from infected wild deer in Saskatchewan, to the east. In 2002, it found CWD in farmed elk and two farmed whitetail deer. The next year, it started sampling wild deer.

In 2005, a wild CWD case turned up. Since then, Alberta has culled deer in an area near the Saskatchewan border and required hunters killing deer in those areas submit the head for disease testing. Now hunters can drop off their deer heads at designated trailers and 24-hour freezers.

Hunters have turned in 17,000 heads, a dozen of which tested positive for CWD. Game agents have taken another 5,000 heads, 36 of which returned positive results. Said Darcy Whiteside, a spokesman for Alberta Sustainable Resource Development: "It's not pleasant work."

Those disease rates are still quite low, comparatively. At the upper end are herds of wild mule deer in Wyoming found to have infection rates around 35 percent.

Michigan marks the 14th state to find a case of CWD, after Wyoming, Colorado, South Dakota, Oklahoma, Kansas, Wisconsin, West Virginia, New York, Minnesota, Nebraska, Illinois, Utah and New Mexico.

To avoid spreading the disease, Richards said, hunters should be aware of transporting those parts of a deer  fluids, organs, brain tissue and spines  most likely to spread the disease.

"The risk of inadvertently transporting the disease home is low," he said. "But the consequences are gargantuan."