Bangtail elk test negative for brucellosis

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Elk capture

Elk are captured by helicopter before having their blood drawn. A portion of the captured elk are collared to monitor their movement.

One hundred samples taken in the last two years from cow elk in the Bangtail Mountains have tested negative for brucellosis exposure, according to Montana Fish, Wildlife & Parks.

The Bangtails are a small range that parallel the Bridger Mountains and are located between the Bridgers and Crazy Mountains in Hunting District 393.

The testing is part of Montana’s broader effort to sample and test cow elk for brucellosis exposure in what’s known as the Designated Surveillance Area. The DSA is spread across southwestern Montana and surrounds Yellowstone National Park.

The goal of monitoring the spread of brucellosis, which began in 2011, is to determine the presence of the disease in elk and understand the movement of elk populations. The research provides data to the Montana Department of Livestock to manage risk of disease transmission between elk and cattle.

Elk were also sampled this year in the Ruby Mountains, HD 322. FWP and DOL announced in February that two among 100 cow elk sampled in the Ruby Mountains tested positive for exposure to brucellosis, indicating they’ve been exposed to the disease. The Ruby Mountains are currently outside but near the boundary of the DSA.

In general, Bangtail elk winter in the foothills from Canyon Creek south to Interstate 90, and east to Highway 89 in the Shields Valley. One elk migrated west shortly after capture in late January to Bridger Canyon and has remained there.

The movement of one Bangtail elk south of Interstate 90 represents the potential for disease interchange between elk populations. Where the elk summered is adjacent to the Wineglass Mountain elk population of HD 314 in the northern Paradise Valley where brucellosis has been detected. Interchange between these two populations would represent a potential transmission route for brucellosis to expand north.

Brucellosis is a disease that can cause pregnant cattle, elk and bison to abort. The disease has been eradicated from cattle in the United States via vaccination programs but persists in wildlife in the Greater Yellowstone Ecosystem.

The bacterial disease can also infect humans, causing undulant fever. Brucellosis is primarily transmitted through contact with infected birth tissues and fluids.

As part of the effort to understand the epidemiology of brucellosis and the actual risk posed by seropositive animals, the birthing sites of seropositive elk that had been captured between 2011 and 2015 were tested for Brucella bacteria. At the end of a five-year monitoring period the elk were trapped and killed to determine if they were actively infected or were simply seropositive (which denotes they have been exposed to the bacteria at some point).

Veterinarians detected Brucella bacteria at three out of four abortion and two out of 61 live birth sites, suggesting that Brucella bacteria is typically found at abortions but not at live births.

Out of 18 necropsies that tested 427 tissues on seropositive elk, Brucella bacteria was found in only three elk.

Based on the information, FWP concluded that Brucella is difficult to culture and that seropositive elk may not harbor widespread infections of Brucella bacteria. 

For more information about brucellosis and the Targeted Elk Brucellosis Surveillance Project, visit

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