a group of bison tested in Wind Cave had a reactor rate of 56%. Custer State Park had a 47% reactor rate.

In April 1961, state and federal animal-health officials met with bison managers of both herds, and a herd plan was devised and agreed on. The plan included blood testing of the entire herd of adults and calves, immediate removal of reactors or permanent identification of reactors with later disposal, and continuing calfhood vaccination with S19. The Wind Cave and Custer bison herds were separated by a fence.

In Wind Cave, the program followed lines of "natural management," and facilities for active control of the herd of 250 bison were not built. In the first blood testing in 1964, 37% of the bison were seropositive (Table IV-1); by 1985, the herd was seronegative. The combination of vaccination, serologic testing, and management with removal of reactor bison allowed Wind Cave National Park to eliminate brucellosis in 21 years.

The program for the bison in Custer State Park followed lines of a commercial ranching operation. Capture facilities were built in 1960-1961. The first herd test, in the winter of 1961, found 119 reactors in 248 bison tested (Table IV-1). Bison were culled annually and sold or sent to abattoirs. All bison calves and yearlings were vaccinated annually. In 1967, the number of bison tested was increased to 2,110; the reactor rate was 5%. In 1973, the herd was seronegative, and in 1974 the park managers reduced the herd size from 1,750 to 1,000. Brucellosis had been eliminated in 10 yr, even though not all bison were tested each year.

The U.S. Fish and Wildlife Service's Wichita Mountains Wildlife Refuge located in Comanche County, Oklahoma, had vaccinated its bison and longhorn cattle for brucellosis since the 1940s. Bison tested in October 1963 were seronegative, but in 1964 brucellosis suspects in elk and bison were found in the fall roundup. The origin of the disease is not known. The program developed for this herd included the following steps: blood-test all bison over 1 yr old in the fall of 1972, slaughter all bison that could not be gathered, send all test-positive bison to slaughter and collect tissues for isolation of B. abortus, divide bison herd into isolated groups on different pastures, conduct a complete herd test in the fall of 1973, discontinue vaccination of bison calves in 1973, and test another species for brucellosis. The Refuge also reduced the size of the herd from 781 to 345 in 1973. It took 8 yr to eliminate the disease, and the herd was considered free of brucellosis in May 1974.

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