Brucellosis in Southwest Montana

Montana Fish, Wildlife and Parks held an elk brucellosis working group meeting last week in an effort to review elk management options and the spread of brucellosis, according to a release from FWP.

Brucellosis is a contagious bacterial infection that can be found in domestic animals and wildlife, and can be transmitted to humans. The disease results in miscarriages or aborting of fetuses in pregnant animals and can cause undulant fever in humans if they come in contact with the brucella pathogen through contaminated meat or unpasteurized milk, according to the Centers for Disease Control and Prevention.

The meeting, led by the elk brucellosis working group, focused on winter activities and results to examine an “effective elk management option and risk prevention efforts in Southwestern Montana hunting districts,” as stated in the release. These areas usually include hunting districts that border or are near Yellowstone National Park, which includes those in Madison County.

“We’ve known brucellosis has existed in wild elk herds for a long time and trying to mitigate and manage elk in regard to brucellosis is something we’ve been working on for a while,” said Greg Lemon, information bureau chief for Montana FWP.

Lemon said FWP is trying to find ways to keep elk from mingling with cattle, especially during calving season. He also said concerns from ranchers and livestock producers in Southwest Montana were the main reasons for the development of an elk brucellosis working group.

What the science says

A new report from the National Academies of Sciences, Engineering and Medicine calls on federal and state collaboration to address brucellosis being transmitted from elk. The release urges efforts be switched to elk management, rather than bison, as elk are now viewed as the primary carrier after the academies released a May 2017 publication titled “Revisiting Brucellosis in the Greater Yellowstone Area.” The publication looks at the history of the disease between elk, bison and the transmission to cattle, as well as populations and case studies.

Between 2002 and 2016, a total of 22 cattle herds and five privately owned bison herds were infected throughout all three states in the GYA, Montana, Idaho and Wyoming, according to the academies research. In Montana alone, seven cattle herds and three privately owned bison herds were diagnosed with brucellosis between May 2007 and November 2016.

“In 1998, we concentrated more on bison because they were heavily infected, especially herds in Yellowstone National Park,” said Eric Liska, brucellosis program veterinarian with the Montana Department of Livestock. “But we have been concentrating more and more on elk as every transmission since 1997 (to cattle) has come from wild elk.”

There has been no evidence of the disease being transmitted from bison to cattle, likely because of the way bison herds are managed.

“The Interagency Bison Management Plan has created a plan to keep separation of bison and cattle and there hasn’t been a transmission because they’ve been effectively managed,” said Liska, adding managing wild elk is much more complicated and complex.

Montana has created a Designated Surveillance Area, which encompasses much of Southwest Montana, as part of the eradication effort. Through extensive testing of cattle and surveillance, the DOL and producers find transmissions before they can spread. All cattle and domestic bison must be tested for brucellosis within 30 days prior to change of ownership or movement out of the DSA if they are sexually intact and 12 months of age or older or intended for breeding purposes. Within the entirety of the DSA, all sexually intact female cattle and domestic bison over the age of four months after the first of the year must be officially vaccinated and identified, as stated in the DSA regulations.

“That’s what the DSA is all about,” said Liska. “We have tested thousands of cattle and have successfully found a number of brucellosis carriers since the DSA was created in 2010. I’m very proud of finding those before they spread within the herd or left Montana.”

Both Liska and the academies publication addressed supplemental elk feedgrounds as host sites for the brucella pathogen to spread. According to the studies and research conducted by a previous Natural Research Council in 1998, the role supplemental feedgrounds play exacerbated brucellosis in elk and no research conducted since 1998 as refuted that. Feedgrounds are areas where officials spread hay for elk to feed on.

Wyoming has an elk feedground program as a special management program that requires additional expenditures for feeding the wildlife, according to Wyoming Game and Fish Department’s website. The feedground is specific to certain hunting districts and requires a special permit.

“We realized that we have herds of elk in Montana that are maintaining the disease in their herds and there’s a cross-species transmission,” said Liska about the possible contamination from Wyoming feedgrounds.

How the disease first made its appearance is still a mystery in the eyes of science.

“There’s a belief through genotyping that (brucellosis) was introduced up to five separate times into the Yellowstone bison in the last century from cattle,” said Liska. “There are stories of an orphaned bison calf feeding on a milk cow and through the milk, the pathogen was transmitted and that’s how pasteurization came about.”

Brucella and the scavenger

The Madison Valley Ranchlands Group is working with the United States Geological Survey to conduct a study and collect data on the viability of the brucella pathogen once it hits the ground. Essentially, the study is aiming to find out how long the disease can be transmitted after the fetus is aborted from the animal.

“The more we know about it, the more we know how to handle it,” said Linda Owens, project director for the MVRG. “We want to know how long the fetuses are staying on the landscape.”

The USGS study will look at how predators impact how long brucella survives – previous studies have determined the pathogen survives longer in cold weather rather than warm.

“The USGS came to us with the study to look at scavengers, mainly birds,” said Owens.

Owens and the rest of MVRG hope that through this study with USGS, the realization of the role predators have will grab more attention.

“It’s a danger for the cattle and hopefully after this study, people will more tolerant of carcasses on the landscape,” said Owens.

Madison County is currently looking into a carcass composting program, which would allow landowners, ranchers, hunters, etc., to deposit carcasses to a designated site and be covered with compost material to decompose while reducing the risk of attracting scavengers.

Eradicating the disease

While the hope of most producers, agencies and groups is to eradicate brucellosis, it is something that will take time and effort from all.

“I never say never but it would take a lot to eradicate the disease,” said Liska, adding the eradication process, along with all the different groups and partnerships involved, is complex and complicated. “A lot of stars would have to align.”

*To read more about carcass composting, check out the article titled “Decreasing attractants” in the June 15 edition of The Madisonian. Or, if you are interested in reading more from the National Academies of Science, Engineering and Medicine, visit www.nap.edu.

 

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