BILLINGS, Mont. (AP) -- An animal disease carried by wildlife in the greater Yellowstone area has been found in a Madison County cattle herd, Montana officials said Thursday.
One cow from the unidentified herd was killed after the animal tested positive for brucellosis in a field test. The infection was confirmed after tissue from the cow was sent to the National Veterinary Services Laboratory in Iowa, said state veterinarian Marty Zaluski.
It's the sixth brucellosis case in livestock in Montana in the last six years, including two infections in bison herds. Before 2007, the state had not had an infection in livestock since 1985.
The infected animal in Madison County previously was tested and found clean in July 2012.
Brucellosis can cause infected animals to suffer miscarriages. Once relatively common across the U.S., it's been largely eradicated but persists in herds of bison and elk in the Yellowstone area of Montana, Idaho and Wyoming.
Zaluski said about half of the 1,000-head Madison County herd had been tested to see if any other animals were infected. Those have all been negative. Tests will also be conducted on adjacent herds.
"We can't get rid of the risk entirely, but we can have a strong enough program where we find these cases very quickly," he said.
Livestock officials suspect diseased elk were the source of the infection.
In the past, brucellosis infections triggered sanctions against the states where the disease was found. But the federal government has since eased those rules. Montana has designated a four-county "surveillance area," including Madison County, that has heightened testing requirements.
Those moves came after Montana temporarily lost its brucellosis-free status several years ago after two infected herds were found within months of one another. Since then, the state has stepped up efforts to find the disease before cattle leave the state and has expanded efforts to determine how prevalent brucellosis is among elk.
"When brucellosis was found in 2007 for the first time in 22 years, it was a real wake-up call," Montana Gov. Steve Bullock said in a statement. "Brucellosis risk management is a collective effort. We've got everyone involved — the Departments of Livestock and Fish, Wildlife and Parks, the state Legislature, USDA-APHIS, ranchers and hunters."
John Youngberg with the Montana Farm Bureau Federation said livestock owners have taken steps to protect their animals, such as fencing in haystacks to keep elk out, and hazing wildlife away from cows.
But he said that's come at a cost to ranchers, and periodic infections are still likely to occur in the Yellowstone area.