Its use in bison continues to be evaluated. Brucella abortus strain 19 brucella vaccines cause vaccinated animals to produce antibodies that are indistinguishable on standard diagnostic tests from the antibodies produced by animals infected with brucellosis. However, the RB51 vaccine does not produce those interfering antibody titers. Brucellosis, a disease that causes abortions and lowered milk production in bovine and bison cows, is transmissible to humans as undulant fever. In humans, this disease causes severe flu-like symptoms that can last for months or years if left untreated.
Humans can contract brucellosis through contact with infected cows, particularly during calving.
Consumption of unpasteurized milk and dairy products can also cause human brucellosis or undulant fever. Excellent progress has been made in the cooperative state-federal brucellosis program in recent years. At the end of March, only 44 cattle and bison herds remained under quarantine for the disease, compared with more than 1,100 five years earlier. Notice of this action was published in the April 1 Federal Register. An original and three copies should be sent to Docket No.