Brucellosis causes pregnant cows to abort their calves. It had been largely eradicated from livestock in the United States before Monday's report of an infection near the town of Pray. The disease has persisted in wildlife in and around Yellowstone National Park.
The infected cow came from the ranch of Art Burns, who said Tuesday that he was aware of the potential dangers of running cattle near the nation's last reservoir of brucellosis.
Pray is about 30 miles north of Yellowstone National Park and adjacent to the Gallatin National Forest.
"We feel terribly about this, but it's part of what comes with living here and being engaged in the business," Burns said in an interview. "You very much want to dodge the bullet. But you have to assume the risk."
His experience underscores the difficulty researchers and livestock officials face in coming up with a solution to brucellosis. Experts say existing vaccines are only about 60 percent to 70 percent effective.
"Ranchers had really made an effort in earlier years to make sure they did not have brucellosis in their herds. Now we're going back to square one and starting over," said John Paterson, a cattle expert with the Montana State University Extension Service.
Although the diseased cow has been destroyed, the discovery will cost the state its federal brucellosis-free status. That will force livestock producers across Montana to undergo costly disease testing and possibly a vaccination program.
Burns said the infected cow had been vaccinated twice before a preliminary test six weeks ago first indicated a possible problem. Confirmation of the disease came on Monday.
Livestock officials said Burns had taken all the appropriate steps to guard against a transmission – by vaccinating and testing his cows frequently for disease.
"I'm working, as my neighbors are and everyone else in this valley is, to manage the situation and move forward with a solution," Burns said.
The cost of containing the disease – including testing all cows intended for out-of-state shipment – could be from $3 to $7 million, Paterson said.
Meanwhile, some other livestock producers already are calling for the state to step up efforts to control brucellosis on another front – in wildlife.
State officials insist its too early to tell if wildlife or cattle were the source of the disease.
"Right now everybody is focused on getting through the testing period and making sure we don't have any more (infected cattle)," said Christian Mackay with the Montana Department of Livestock.
Mackay said Burns was in discussions with federal agriculture officials about whether the rest of his herd will have to be slaughtered.
That happened last year to a rancher near Bridger who lost almost 600 cows, bulls and calves after seven of his animals tested positive for the disease. The May 2007, outbreak put Montana on probation if another infection was reported within two years.
It will now be at least a year before Montana regains its disease-free status.
Burns said he would not speculate on the source of the disease but would continue to cooperate with state and federal livestock officials conducting the investigation.