Brucellosis, caused by Brucella abortus, is enzootic among the free-ranging bison (Bison bison) herds of Yellowstone and Grand Teton National Parks (Wyoming), Wood Buffalo National Park (Canada), and a privately owned herd in South Dakota. There have previously been numerous infected herds, both private and public. The presence of the disease in the free-ranging bison and possible control measures have led to much controversy among ranchers (who fear transmission to cattle), governmental agencies, environmentalists, and other interested individuals and organizations. Lawsuits, many meetings, media publicity, and other reactions to the problem have occurred. The climax came during the winter of 1996–1997, when over 1000 bison were slaughtered as they migrated from Yellowstone National Park and an additional 600 starved because of the severe weather.