Spokesman Edward Marszalek of the forest supervisors in Krosno says six bison that appear to be sick will be shot and their bodies tested for the disease.
Officials plan to inoculate the rest of the 300-strong herd.
Marszalek said Friday that some 30 calves are born each year, and that removing six animals won't deplete the herd.
The rare bison is Europe's largest land mammal and lives in reserves in southern and eastern Poland. It is related to the North American buffalo.