Late 1960s

Deer begin dying in captivity from a mysterious wasting illness at Foothills Wildlife Research Facility in Fort Collins, Colo. Later, some of the deer are returned to the wild.

1977

Colorado State University graduate student Elizabeth Williams is the first person to identify the deer ailment as a type of brain disease known as a spongiform encephalopathy, similar to scrapie, a fatal illness reported in sheep since the 1700s.

1982

Stanley B. Prusiner, a microbiologist and neurologist at the University of California at San Francisco, reports evidence that scrapie is caused by a protein that replicates itself without genetic material. Prusiner calls his discovery a prion. Prions later will be linked to chronic wasting and mad cow diseases, as well as to variant Creutzfeldt-Jakob disease in humans.

1986

Bovine spongiform encephalopathy — “mad cow disease” — is reported in the United Kingdom.

1990

Chronic wasting disease is found in free-ranging white-tailed deer in Colorado and Wyoming.

1995

A variant of Creutzfeldt-Jakob disease appears in Britain. A year later, the government there acknowledges that mad cow disease has jumped the species barrier from cattle to humans.

1999 to 2001

During three consecutive fall deer hunts, Wisconsin tests a total of about 1,000 deer for chronic wasting disease and tuberculosis at numerous locations in the state.

2002

Feb. 28

The Wisconsin Department of Natural Resources announces that three deer killed the previous November near Mount Horeb test positive for chronic wasting disease. It’s the first discovery of the disease east of the Mississippi River and raises concern about the safety of Wisconsin’s dense white-tailed deer population.

March 5

The DNR and other state agencies designate a 415-square-mile surveillance area in parts of Iowa and Dane counties where deer will be shot and tested for the disease.

March 20

The state begins a round of public meetings on the disease in Mount Horeb. The gathering draws about 700 people. A little more than a month later, about 2,000 attend a second meeting in Mount Horeb, indicating the rising level of concern in the area.

April 4

The state department of agriculture imposes an emergency ban on deer and elk shipments into Wisconsin as part of a strategy to limit the state’s exposure to the disease.

April 18

With tests showing an estimated 3% of the deer in the area afflicted with the disease, the DNR announces a plan to kill most of the deer in a 361-square-mile zone. The eradication zone eventually grows to 411 square miles as more sick deer are discovered. The agency also proposes cutting the deer population by half in a broader region covering parts of 10 counties.

May 16

The Legislature approves $4 million in funding and grants wildlife officials new powers to battle the disease, including authority to shoot deer from aircraft.

June 25

The DNR bans baiting and feeding of deer and approves liberalized bag limits in the eradication zone and the surrounding 10 counties.

Sept. 13

The last of four weeklong special hunts in the eradication zone west of Madison ends. The total number of deer killed in the four weeks is nearly 1,500.

Sept. 19

The agriculture department announces that a buck on a hunting preserve in Portage County killed by a hunter earlier in the month tested positive for chronic wasting disease. It’s the first infected animal found on a Wisconsin game farm. By the end of the week, the agency has quarantined three game farms — the one in Portage County where the infected buck was killed, and two in Walworth County. Later, another is quarantined in Dane County.

Sept. 25

State officials begin another round of public hearings on chronic wasting disease. Three cabinet secretaries, along with representatives of several state agencies, make presentations and take questions on the state’s plan to control the disease.

Oct. 9

State lawmakers release another $2 million to help fund Wisconsin’s fight against chronic wasting disease.

Oct. 15

An agreement between the state and the U.S. Department of Agriculture gives Wisconsin hunters the ability to test an additional 200,000 deer for chronic wasting disease. The testing capability comes in addition to the 50,000 deer the state already wanted to test.

Oct. 17

A second game-farm deer is found infected. The total number of deer identified with chronic wasting disease stands at 42, with 40 from the wild.