While bison in Yellowstone National Park draw the most attention for the potential to spread brucellosis to livestock in the surrounding states of Montana, Idaho, and Wyoming, genetic studies indicate that elk are most likely behind the disease's spread in the region.
A small story in the fall issue of Yellowstone Science discusses that conclusion.
A DNA genotyping study conducted in 2009, and which was just recently published in the Journal of Wildlife Diseases, examined samples from 10 bison, 25 elk, and 23 cattle collected in the greater Yellowstone area between 1992 and 2003 and found that DNA markers for Brucella abortus were nearly identical in elk and cattle but "highly divergent" from those in bison.
"The data, which suggest that elk rather than bison are most likely the origin of recent outbreaks of brucellosis in Greater Yellowstone cattle, are consistent with the fact that elk comingle with cattle more often than do the wild bison, which have been managed to prevent dispersal outside established conservation areas," notes the Yellowstone Science article.
Some might not find that conclusion too surprising in light of the fact that there has never been a documented case in the wild of a bison transmitting the disease to cattle, while it has been seen with elk populations.
Brucellosis is a disease that can cause spontaneous abortions in livestock. The state of Montana currently is one of just two states that carry a "brucellosis-free" tag on their livestock industries. Losing that status can be costly, as it impacts the marketability of Montana cattle and ranchers must pay to test all their cattle for brucellosis.
As a result, Montana officials have been particularly aggressive about seeing that any bison that try to leave Yellowstone in spring are hazed back into the park after a certain date. Those hazing operations have at times drawn national attention due to injuries sometimes sustained by bison, and in part due to the efforts of the Buffalo Field Campaign, a non-profit activist group that works to illustrate the adverse treatment inflicted on some bison during hazing.
In an interview with the Traveler back in June, Dr. Marty Zaluski, the state veternarian for the Montana Department of Livestock, said that while there are efforts in his state to address brucellosis in elk and to prevent the spread of the disease from these ungulates -- efforts that range from keeping cattle and elk separate during calving seasons and even "strategic hunting" -- the high-profile debate over bison stems in large part from the efforts of the Buffalo Field Campaign.
"And not only that, but bison are so photogenic and people of the United States feel such an attachment of tradition and history to bison that really, bison typically hog, I shouldn’t say hog, but certainly get a lot of the media attention," Dr. Zaluski added at the time.
Yellowstone officials currently are writing an environmental impact statement on a proposal to vaccinate bison against brucellosis.