Results from 5 wild whitetails could prompt new strategy by state.

For the first time, chronic wasting disease has been found in wild deer killed outside the 411-square-mile eradication zone southwest of Madison, suggesting that the state may have to broaden its strategy against the disease.

The Department of Natural Resources announced Friday that four deer in Iowa County and one deer in Richland County, all killed during the fall hunt, had tested positive for the fatal brain disease.

All were found outside the zone near Mount Horeb where the disease was discovered in Wisconsin and where officials plan to wipe out the entire deer herd in a bid to prevent the disease from spreading.

“It’s a disappointment,” said Tom Hauge, the DNR’s wildlife director, about Friday’s test results.

“Finding any more (new cases of the disease) is problematic,” said Jeff Davis, a spokesman for Whitetails Unlimited, a national deer hunting group based in Sturgeon Bay. “Finding any outside the zone is certainly not good news. . . . I imagine they’ll extend the eradication zone, and the larger the zone gets, the harder it is to manage.”

A concentrated area But the news was not entirely disheartening.

The new cases were all found in an area immediately surrounding the zone, an area officials were already focusing on as the most likely new location for the disease.

So far, infected deer have not been found all over the state, a scenario that has haunted hunters and wildlife officials since Wisconsin announced the discovery of its first cases in February.

But test results on more than 29,000 deer have yet to come in. And the majority of the deer awaiting testing come from counties outside the eradication zone and the surrounding area.

For now, Hauge said, the disease “still appears to be fairly concentrated in the southwest corner of the state.”

The new cases were all found to the west of the eradication zone. The farthest afield was the deer in Richland County, which was killed about 16 miles from the border of the zone.

Hauge said it would have been worse if the new cases had been dispersed to all sides of the zone.

But the first cases of infection outside the zone are “potentially very significant,” said Judd Aiken, a professor in the Department of Animal Health and Biomedical Sciences at the University of Wisconsin-Madison.

“It’s pretty clear that the DNR will have a decision to make at some point,” Aiken said. “Do you expand the eradication zone? Create a second eradication zone?”

Aiken said the new cases outside the zone were not totally unexpected, particularly after the disease was found in farmed deer in Walworth County. Deer have escaped from farms in the state, including one infected deer that roamed for six months after escaping into the wild. Officials have feared that escaped captive deer might spread the infection to wild deer in areas previously considered free of chronic wasting disease.

“Once we started seeing the disease in those game farms, when that happened, I went from cautiously optimistic to pessimistic,” Aiken said.

Hauge said there is no evidence that deer farms played any role in the new cases of infection outside the zone.

Early study of the disease suggests that it probably entered Wisconsin in 1996 or 1997, Hauge said, adding that, as more information comes in, it may turn out that the disease arrived here even earlier.

No immediate zone change For now, Hauge said the eradication zone won’t be expanded based on the new cases. But the state will offer landowners in the new areas the chance to shoot more deer. Officials want to kill more deer in the new areas so they can test them and get a better sense of how much of the deer population there is infected.

So far, tests indicate that just over 2% of the deer in the eradication zone have the disease.

But Hauge said the state isn’t likely to consider changes such as expanding the eradication zone or creating new zones for another eight to 10 weeks, until a clear picture has emerged of precisely where the disease has spread. By then, all the test results should be in from samples of deer killed outside the eradication zone.

Another concern for Wisconsin has been the counties bordering Illinois, which reported its first case of chronic wasting disease in November.

One of Illinois’ infected deer was found in northwest Boone County, within five miles of the Wisconsin border.

But Hauge said results have come back on more than 80% of the samples of deer killed in border counties such as Green, Rock and Walworth. So far, none of those deer has been infected.

With the results release Friday, about 24% of the 38,000 samples being tested for chronic wasting disease have been analyzed.