White-tailed deer populations in parts of Eastern Montana and elsewhere in the Northern Plains could take years to recover from a devastating disease that killed thousands of the animals in recent months, wildlife officials and hunting outfitters said.

In northeast Montana, officials said 90 percent or more of whitetail have been killed along a 100-mile stretch of the Milk River from Malta to east of Glasgow. Whitetail deaths also have been reported along the Missouri and Yellowstone rivers in western North Dakota and Eastern Montana and scattered sites in Wyoming, South Dakota and eastern Kansas.

The deaths are being attributed to an outbreak of epizootic hemorrhagic disease, or EHD. Transmitted by biting midges, EHD causes internal bleeding that can kill infected animals within just a few days.

"I've been here 21 years and it was worse than any of us here have seen," said Pat Gunderson, the Glasgow-based regional supervisor for Montana Fish, Wildlife and Parks. "Right now it's going to take a few years to get things back to even a moderate population."

In North Dakota, state wildlife chief Randy Kreil described the outbreak as the most extensive and deadly in two decades.

Mule deer, bighorn sheep, elk and pronghorn also are susceptible to EHD, but it is particularly damaging to whitetail herds, animal health experts said. Livestock can be infected but typically show few symptoms.

Researchers say the virus that causes EHD does not infect people and there is no risk of eating or handling infected deer,

More precise estimates of the number of whitetail killed are expected after agencies conduct winter population counts and survey fall hunter success.

Periodic outbreaks of EHD occur in whitetail herds across the country. Wildlife officials say the outbreak in the Northern Plains stands out for the high number of deaths and wide area affected.

Animal health experts suspect it was triggered by an exceptionally wet spring that led to lots of muddy breeding habitat for the biting midges that carry the disease. A warm fall meant the midges lingered and continued transmitting EHD to deer.

The outbreak followed a harsh winter that already had knocked down deer numbers across the region.

In response to those winter deaths, Gunderson said the number of hunting tags offered in northeast Montana was reduced from 5,000 to 4,000. After the EHD outbreak began in late summer, sales of another 2,000 tags were suspended.

In western North Dakota, 1,500 licenses were suspended and the state offered refunds for deer tags already sold. More than 630 people took advantage of the refunds, said Randy Meissner, license manager for North Dakota Game and Fish.

Hunting outfitter Eric Albus in Hinsdale said his business ran one archery hunting trip along the Milk River this fall, compared to 40 or 50 hunts in prior years.

"It was horrendous," Albus said, "especially when you couple it with the fact that we lost 40 to 45 percent of our whitetail in the winter."

To satisfy his customers, Albus said he leased alternate properties to hunt on that were up to 350 miles away from Hinsdale.

In southern states where deer have a history of exposure to EHD, death rates from the disease are relatively low, said David Stallknecht with the Southeastern Cooperative Wildlife Disease Study, which has been tracking EHD for more than 30 years.

Whitetail in northern states are more likely to die because they lack the antibodies from previous exposures needed to help fight off the disease, said Stallknecht, a professor in the College of Veterinary Medicine at the University of Georgia.

He said a better picture of the outbreak will come later this year, after state wildlife agencies from across the country submit annual animal mortality data to the Southeastern Cooperative

Notwithstanding the disease's economic impacts to the region's hunting industry, Gunderson said the loss of so many deer along the Milk and Missouri rivers could have an upside.

Along some stretches of the river, a combination of animal grazing and ice jams scraping the riverbank each winter have prevented cottonwood trees from regenerating for decades.

After the region's record spring floods allowed seedlings to take root high up on the banks, where they are more protected, Gunderson said a new crop of trees could thrive with so many whitetail gone.

"We won't have the tremendous deer population browsing on them, so hopefully we'll get the cottonwoods along these river bottoms that will take us through the next 100 years," he said.