By STEVE KARNOWSKI | Associated Press

MINNEAPOLIS (AP) — Tests on more than 750 ducks shot by Minnesota hunters this fall have turned up no signs of the kind of bird flu that devastated the Midwest poultry industry earlier this year, according to data released by the Department of Natural Resources on Thursday.

Wildlife agencies are testing wild waterfowl to see if ducks and geese flying south for the winter are carrying highly pathogenic forms of avian influenza such as H5N2, which could provide an early warning if the disease returns. Scientists believe that wild birds, primarily ducks, are the main carriers of the dangerous H5 bird flu viruses that began showing up in North America last November.

Wild waterfowl don’t normally get sick from these viruses, but they’re deadly to domestic poultry. Bird flu cost producers more than 48 million chickens and turkeys before the outbreak ended with the onset of warm weather in June. Minnesota and Iowa were by far the hardest hit states.

DNR wildlife research manager Lou Cornicelli said none of the 753 Minnesota duck samples tested so far came back positive for highly pathogenic flu strains. About 19 to 21 percent tested positive for low pathogenic bird flu, which isn’t considered a threat. Those “low path” figures are “completely normal” and actually validate the agency’s sampling methods, he said. Results from 100 more samples submitted Wednesday are pending.

The tests had a 95 percent chance of detecting the disease if it was present in 1 percent of the population, Cornicelli said, so it’s possible that the survey missed some infected ducks or that other infected ducks will arrive later.

Cornicelli was reluctant to draw conclusions about what the absence of findings so far means for a poultry industry that has been bracing against the possibility that migrating birds could bring the disease back to the Midwest or spread the disease to major poultry states in the South and East that escaped earlier.

“I don’t know if it’s good news or if it’s not good news,” Cornicelli said.

The fact that highly pathogenic viruses weren’t found in these samples doesn’t mean they’re not present in wild birds, said David Halvorson, professor emeritus of avian health at the University of Minnesota. There could be a lot of explanations, he said. There might be a problem with the sampling method, maybe it’s too early in the season, or perhaps mallard ducks aren’t the main carriers and some other bird species is responsible, he said.

Poultry producers certainly aren’t ready to relax.

“We aren’t letting our guards down any time soon and we continue to be vigilant so that we are as ready as we can be for any future introductions of avian influenza,” said Steve Olson, executive director of the Minnesota Turkey Growers Association. “We obviously hope we won’t see it but we want to be prepared.”

For all the losses the poultry industry has suffered, comparatively few cases of H5 viruses have been found in wild American birds in the past year. U.S. Department of Agriculture biologists and their state partners began a major national wild bird surveillance effort July 1, but the agency has confirmed only one positive case from more than 13,700 samples so far, USDA spokeswoman Gail Keirn said. That was a mallard duck in Utah that tested positive in August. Before that, only 100 wild birds had tested positive in the U.S. since last December, including only two in Minnesota, a hawk in April and a chickadee in June.

The DNR plans to collect at least 200 more samples as the hunting season continues to get more data on late-migrating ducks, Cornicelli said, focusing on vulnerable poultry-producing counties.