Brucellosis in bison greatly exaggerated
There has never been a case of brucellosis transmission from wild bison to cattle in natural conditions. Yet, since 1985, approximately 4,000 bison from the Greater Yellowstone Area have been sent to slaughter. Wild bison seem to have an immunity, and while 45 percent may test serologic positive, meaning they have been exposed, few test positive on a culture screen. Brucellosis cannot survive long in sunlight or heat, drastically reducing exposure potential.
The distribution of cattle around Yellowstone makes exposure a very remote possibility. The time cattle are grazing and bison are grazing outside the park is mostly not coinciding. Only first-time pregnant cows giving birth pose a risk at all if they are actively infected. Predators cleaning up afterbirth further reduces exposure potential. All factors combined reduce exposure potential to practically zero.
There might be other rationales for keeping the Yellowstone bison numbers in check (at 4,000 to 3,000), but brucellosis is not a legitimate one. In Grand Teton National Park, where cattle and bison have coexisted for decades, there has not been a case of transmission. Alternative solutions to bison coming out of the Park to graze is to allow them plenty of areas to do so and to distribute excess bison other places in Montana such as reservations, preserves, open ranges and motivated ranches.
Elk seem to be an emerging problem. Elk feeding grounds and migrations among herds may pose a man-made risk, but a greatly exaggerated one.
Roger Hewitt
Great Falls
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