According to Tom Roffe, chief of wildlife health for the U.S. Fish and Wildlife Service, the results are not satisfying: `[The vaccine] confers some immunity in cattle, but it is not great,` he said, noting that cattle in Wyoming that had been vaccinated still contracted brucellosis in 2003. `We know [the vaccine]`s not highly effective in bison.`
Furthermore, Roffe said, tracking and vaccinating 4,900 wild bison is not like giving shots to animals in pens. Given the low level of protection the vaccination affords, he said, it is not worth the expense to vaccinate the park`s herds until a better vaccine is available.
Steven Olsen, a researcher at the USDA`s Animal Research Service, said promising work is underway. `There are new vaccine strains, and new technologies have been developed to make more strains,` Olsen said. `Completing the research is not simple. It is going to be years.`
In the meantime the state of Montana has started a plan to create a brucellosis-free bison herd. State rangers have captured 14 Yellowstone bison and plan to capture and quarantine 200 more. The animals go through repeated tests, a process that takes months, to determine whether they are brucellosis-free.
The herd will then be bred and relocated in the wild, but not in Yellowstone, where they would again be exposed to brucellosis. The brucellosis-free bison will remain free-ranging outside the park, since they will pose no threat to livestock.
Now the state is planning to slaughter female elk that test positive for brucellosis at one of its feeding grounds this winter as part of a test program. But Wyoming doesn`t expect its elk-kill to grab headlines or draw protesters the way Montana`s bison hunt has. `The bison are icons, because they are in Yellowstone,` said Aasheim of Montana`s wildlife department. `But until there`s a solution, we are going to use hunting as a tool to manage them.`
Source: www.vetscite.org
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