Bison are native to the Greater Yellowstone Area and were observed there by early travelers both before and after the creation of
Hunting and poaching of bison in the late 1800s substantially reduced the number of bison in the
By 1922, the park suggested that a law be passed authorizing the sale or disposition of some bison (Albright 1922, as cited in Skinner and Alcorn 1942–1951). Authority for this was granted in the Appropriation Act of 1923.
By the 1930s, the total number of bison wintering in the Lamar area had increased to over 1,000, and the park began reductions by shipping bison to public parks, zoos, and private estates. Bison were also used to begin herds in other areas of the park. Artificial feeding of the
In 1967, when herd reductions in the park ceased as part of a larger redirection of park policies, 397 bison were counted. Since that time bison, elk, and other animals have been allowed to reach population levels dictated by environmental conditions.
Brucellosis was first diagnosed in the
Brucellosis is a contagious bacterial disease, caused by various species of the genus, Brucella, that infects domestic animals, wildlife, and humans worldwide. Brucella abortus is the species that infects both cattle and bison. There is no cure for brucellosis in these species. Vaccines developed so far are not 100% effective, and are to date less effective with bison than with cattle. The first known case of brucellosis in the bison herd was reported in 1917. It is generally agreed that the transmission of brucellosis to the
In cattle, the organism is shed primarily in aborted tissues, reproductive tissues, and discharges, especially just before, during, or soon after abortion or live birth. Ingestion by other cattle of contaminated material is the primary route of infection. Cows infected with brucellosis characteristically abort their first calf after the fifth month of gestation.
Less is known about the disease in bison, particularly free-ranging bison. Transmission from bison to cattle has occurred under experimental conditions in confined spaces, but has not been documented under free-ranging conditions. Since the release of the Draft Environmental Impact Statement, the National Academy of Sciences finalized a summary of pertinent literature on several aspects of brucellosis (NAS 1998). Relevant material from this summary is used throughout volumes 1 and 2 of the final environmental impact statement to clarify discussions on epidemiology and pathology of the disease in both cattle and bison.
Diagnosis. In cattle, diagnosis is based on the results of blood tests, herd history, clinical signs, and other information. The diagnosis can be confirmed by positive cultures. B. abortus may be isolated from tissues collected at slaughter, milk or udder secretions, biopsy of lymph nodes, reproductive tract exudates, discharges from live animals, or fetal or placental materials collected at the time of abortion or calving. In
Risk of Transmission. Scientists and researchers disagree on even some of the most basic factors influencing the risk of transmission. These include whether studies on cattle are applicable to bison, whether controlled studies are applicable in the field, and the best ways to conduct additional research to determine the risk of transmission.
These disagreements and a paucity of information on brucellosis in bison make it impossible to quantify the risk of B. abortus transmission from bison (and elk, although the environmental impact statement does not analyze brucellosis in elk) in the
Since bison and cattle are prevented from interacting under each of the alternatives in the environmental impact statement, it is the presence and persistence of bacteria in birth materials that are at issue in determining the risk of transmission. Research completed since the release of the Draft Environmental Impact Statement has direct bearing on this discussion. In one study, 30 known bison birth or abortion sites in the park from 1996 to 1998 were sampled. The B. abortus bacterium was isolated at two of those sites immediately following the birth or abortion event and persisted for a maximum of 18 days (Coffin, pers. comm.). Cook (1999) studied B. abortus strain RB51 on samples taken from the exposed surface of bovine fetuses in
Alternative Interpretation of Risk. The above information represents areas where scientists generally agree on the interpretation of available data. However, considerable debate and need for additional research remain. The bulk of brucellosis research and disease management has focused on domestic livestock, yet limited published information suggests the disease may be transmitted differently and have different clinical, pathological, and population effects in bison (Williams et al. 1994; Meyer and Meagher 1995a).
Those who suggest the risk is negligible point out that there have been no documented cases of brucellosis transmission from wild, free-ranging bison to cattle.
It is possible that, although brucellosis may be endemic in the
Bison may also enter national forest
land in the Eagle Creek/Bear Creek area east of Reese Creek, where they
occasionally enter private lands in the Gardiner area by traveling along the
From the west side of the park, bison
move along the
Brucellosis (B. abortus) has the following direct impacts on the livestock industry:
The presence of livestock disease may also affect each state’s classification by the Animal and Plant Health Inspection Service.
Did You Know?
Yellowstone contains approximately one-half of the world’s hydrothermal features. There are over 10,000 hydrothermal features, including over 300 geysers, in the park.