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Disease Threats to Elk
Photos and text by Eric Fowler
Published October 2010

Disease Threats to Elk Other than man and a handful of mountain lions, there are no predators to really stem the growth of elk herds in Nebraska. Disease, however, could be another story. Disease concerns played a major role in changes being made at Fort Niobrara National Wildlife Refuge, specifically when three deer harvested within 20 miles of the refuge in 2006 tested positive for chronic wasting disease, a contagious neurological disease that damages the brain and central nervous system of deer, elk and moose and is always fatal.

Since first appearing in Nebraska’s free ranging deer in 1998, CWD has been found in four captive elk herds in the state. Three of those herds were destroyed, a standard practice meant to reduce the chances of developing a hot spot that could spread the disease to free-ranging deer and elk. The fourth, located in Cherry County, was quarantined but cleared after extensive testing of the remaining animals. Since it was established nearly 100 years ago, the Fort Niobrara refuge’s defined purpose has been the preservation of native birds, bison and elk.

“Knowing that we have responsibility to manage for elk, we just felt we’d be derelict in our duties to stick our head in the sand and wait for CWD to show up and have to kill all of these [captive] elk,” said Todd Frerichs, deputy project leader at the refuge.

Since 1997, the Commission has tested more than 42,000 deer and 50 wild elk for CWD, most of them harvested by hunters. Of those, 202 deer and two elk have tested positive. Both elk positives came from cow elk in Sioux County: one harvested during the 2009 hunting season, and another sick animal that was put down in January 2010. Bruce Trindle, big game research and wildlife disease specialist in the Commission’s Norfolk office, said the disease spreads slowly through or between deer and elk populations at first, a fact that may have delayed its inevitable appearance in Nebraska’s elk.

As prevalence rates rise, however, it spreads more rapidly. In Wyoming, the prevalence rate in some elk herds is 40 percent or higher, resulting in a measurable population decline. Animals can be infected for months or years before becoming sick. “There isn’t any immunity, and if a deer or elk gets it, they die,” Trindle said.

Another threat to Nebraska’s elk herd unexpectedly appeared in 2009 when an elk in a captive herd in Knox County and a beef cow in Rock County tested positive for bovine tuberculosis, a highly infectious bacterial disease that can infect and be passed between any warm-blooded vertebrate. When found in cattle, tuberculosis can have dire consequences for both the ranch and state in which it is found due to restrictions that are placed on livestock movement. Testing found no other cases in Nebraska livestock or in 42 deer culled and tested around the captive elk herd. Had it been passed through the fence to free-ranging wildlife, Hams said, the result would have been “catastrophic.”

An area of Michigan continues to deal with tuberculosis in deer and livestock 30 years after it was discovered, an effort that has included reduction of the local deer herd. Hams said the case provides further justification for ending the practice of raising elk and other wildlife behind fences for meat, antlers or recreational shooting. Testing programs for captive herds are “rudimentary and almost ineffective,” Hams said.

Often diseases aren’t discovered until animals are sick and dying or, in the case of tuburculosis, until an animal is slaughtered. By then, Hams said, other elk from the same herd, which may have been infected, have been shipped to other elk farms around the country, spreading the infection. Captive elk can and sometimes do escape from pens, putting free-ranging wildlife at risk. But diseases can also spread when captive and free-ranging wildlife meet at fencelines, which is why the Commission continues to shoot wild elk found in close proximity to a captive herd.