A deadly disease that likely would devastate Indiana's deer population is knocking at the door. And experts say it is a matter of when — not if — it comes barreling in.

Chronic Wasting Disease, which is fatal for any deer that contracts it, has been found in three neighboring states. In two of them, Michigan and Illinois, deer with CWD have been found within 30 miles of the Indiana border.

"Indiana cannot be surrounded on three sides and not have it come in at this point," said Joe Bacon, an avid hunter and president of the Indiana Deer Hunter's Association. "Hunters and Hoosiers are and should be scared of the disease reaching Indiana."

"Someone once told me this is Pandora's box opened up," he added, "and I believe it."

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Bacon is not alone in his concern of the devastation the disease can bring.

Deer numbers will dwindle, either through the disease itself or efforts to control its spread. With that, experts worry that hunting will also take a dive and businesses or communities that rely on hunting could struggle. And other programs and services could suffer as funds are diverted to disease management.

"We view the disease as being one of the most pressing threats to hunting and deer management in the U.S. We fully believe it is that big of an issue," said Kip Adams, the conservation director for the Quality Deer Management Association.

"As soon as it arrives, it changes everything for hunters," he added. "All of the additional regulations it brings are necessary to protect future herds, but suddenly deer season and hunting as you remember it is gone."

Humans help spread deadly disease

CWD is a contagious neurological disease that affects deer, elk and moose. When an animal is infected, its brain degenerates, which often results in emaciation, abnormal behavior, loss of bodily functions and ultimately death.

The disease has no cure or preventative measures at this time, according to Emily Wood, executive director of the Indiana Wildlife Federation. So if an animal is infected, it will die.

The exact origin of CWD is unknown, but it was first found in Colorado in the 1970s. Many believed that it would take more than 100 years for the disease to work its way east, the Mississippi River serving as a natural border. That, however, was not the case. CWD made it across the river and landed in Wisconsin in 2002.

"Since then it has grown very rapidly to be in more than 25 states and seems to grow almost monthly to a new county or state," Adams told IndyStar. "With the help of humans, it moves very quickly."

The disease is believed to spread through saliva, urine or feces from live deer or through contact with high-risk parts such as the backbone, eyes or spleen of harvested deer. The disease can spread through the natural movement of deer, Wood said, but it spreads farther and quicker when humans move the deer.

That most frequently is the case with captive deer hunting operations, where businesses will move deer from one state to another. A law was passed to allow fenced hunting in Indiana in 2015.

Despite the possible symptoms of the disease, it often can take years for them to show and be nearly impossible for a hunter to tell if the deer is infected.

"Once confirmed in Indiana," Bacon said, "I’m not sure any responsible deer hunter would or should eat a deer without it being tested."

There currently is no evidence that CWD can affect humans, but both the Centers for Disease Control and the World Health Organization encourage people to not eat deer that tests positive.

CWD could devastate hunting

The question of when it will arrive in Indiana is still a guessing game, according to Nancy Boedeker, the state DNR's wildlife veterinarian and CWD expert.

Seeing it creep closer in the last few years, she said it's realistic to think that it could possibly arrive in the next year. John Goss, former director at both the DNR and state Wildlife Federation, said he also thinks it could reach Indiana as soon as this hunting season.

"The economic impact will be huge," he said. "If it's here, there would be testing of a much larger population of deer, and that's a rapidly growing expense."

If DNR is having to put additional resources into the management of the disease, that means it has less money to go toward things such as habitat enhancement and other state programs and conservation services.

Indiana has already stepped up its monitoring efforts this year, though testing is not mandatory. The agency has identified several counties neighboring near where the deer has been detected in Michigan and Illinois for enhanced surveillance. In those areas, it is asking hunters to have their harvested deer tested for the disease.

Boedeker said they have seen more hunters participate compared to previous years, which she hopes will continue.

That testing would become mandatory, however, if the disease is detected in Indiana. It also would set in motion a response plan, though Boedeker said the specifics would differ depending on the specifics of the detection.

"It's a permanent drain on resources to manage," she said. "They're an important part of the heritage here and so many people enjoy and rely on the deer, and we want to project them for everyone."

There's no stopping it, only slowing

Still, Bacon said there is no stopping it, only slowing it.

"The landowners and sportsmen will be upset because the only thing shown to show any sign of slowing down is a mass reduction of a deer herd, or going as close to zero in a given area as possible," he told IndyStar. "But what does that do to the businesses and locales supported by deer hunting?"

He said said there will be fewer mature and trophy deer, and Bacon worries some hunters will drop the sport.

Adams acknowledges that this process can have negative impacts for hunting, but he said an aggressive approach with reductions and regulations are absolutely necessary to prevent the disease's spread from getting worse.

That didn't happen in Wisconsin, he said, as the management decisions were based on politics rather than science.

"Hunters thought they were getting what they wanted with a less strict approach to managing CWD, but in the long run it's coming back to bite them," Adams said. "No one has beat this yet; nothing has proven to be successful in the face of CWD."

"But the states that are doing the best jobs," he added, "are the ones where the agencies and hunters are working together."

Illinois found CWD around the same time as Wisconsin, according to Adams, but took a very different and much stronger approach that included sharp-shooting almost immediately. While it is still spreading in Illinois, it's at a smaller rate and in a smaller area than it's northern neighbor.

Goss, the former DNR director, said that he saw deer thrive after being reintroduced in Indiana several decades ago, and hates to think that those conservation efforts could be diminished.

"One of DNR's greatest accomplishments as an agency is the restoration of a wild deer herd," he said. "That will be all undone if we have a deer herd with an incurable disease. It will be a serious setback."

Call IndyStar reporter Sarah Bowman at 317-444-6129 or email at sarah.bowman@indystar.com. Follow her on Twitter and Facebook: @IndyStarSarah. Connect with IndyStar’s environmental reporters: Join The Scrub on Facebook.

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.