Yellowstone National Park is no longer seen as the main source of brucellosis infection in elk living in Montana, according to Neil Anderson, Fish, Wildlife and Parks’ wildlife lab supervisor.
“We are maintaining brucellosis in our elk without any outside influence,” he told the FWP Commission on Thursday.
Within southwestern Montana’s Designated Surveillance Area for brucellosis, FWP has identified 21 different winter ranges that hold about 30,000 elk, according to Kelly Proffitt, FWP wildlife biologist. Some of those elk travel into Wyoming and Idaho, making containment of diseased elk very difficult.
Since density of elk is seen as the main way for brucellosis to spread – a large group is considered 300 animals or more — FWP is trying to understand where elk bunch up so that cattle might be excluded from those areas during the times that elk give birth. It is from the birthing material that live brucella abortus bacteria can be transmitted to other animals.
The areas within the DSA with the highest elk densities are the southern Madison Valley and the Wall Creek Wildlife Management Area south of Ennis. Elk counts at the WMA in winter have gone from around 1,100 in 1987 to about 3,000 in 2010.
Brucellosis has been a difficult disease to fight.
In the 32 years that Montana Fish, Wildlife and Parks has been monitoring the brucellosis in elk, it has spread from a limited area near Yellowstone National Park to south of Dillon and Livingston.
In 1985 and 1986, two hunters are believed to have contracted the disease from infected elk. Brucellosis in humans is known as undulant fever.
The spread of the disease has become a huge issue for the livestock industry, since it can also infect cattle and reduce tolerance for elk on the landscape. That’s important since there is a lot of winter range on private land.
Starting about six years ago, Montana began seeing some significant jumps in the exposure of elk to brucellosis. That may have been partly attributable to a testing method, called the Western Blot test, that was detecting false positives. But Wyoming wildlife officials have also noted that elk on the state’s feedgrounds seem to cycle through high and low periods of brucellosis exposure. Why that is is not known.
The difficulty with containing the disease, for wildlife managers, is that although an animal may be trapped in one area for testing in the winter, it may be found in an entirely different area in the spring and fall. Elk can move very far.
Wildlife biologists also don’t know how long an elk will continue to test positive for the disease. One elk in Wyoming tested positive, but after it was removed from the population it tested negative.
Out of eight elk FWP captured in 2010, only five tested positive when they were recaptured the following year.
Based on its work, Anderson estimated that elk exposure to brucellosis has increased from about .04 percent in 2001 to 11 percent in 2011 in Montana’s Designated Surveillance Area. These exposure rates are close to what Wyoming sees on its feed grounds.
In 2013-14, the testing will move to the southern Tobacco Root Mountains. Other areas of concern are the lower Shields Valley and the Eastern Front of the Absaroka Range.
Post was written by Brett French, Outdoors Editor for the Billings Gazette