ARCO, Idaho - More than 50 cattle have been slaughtered in eastern Idaho after veterinarians confirmed brucellosis infections, a finding that could cause the state to lose its brucellosis-free status.
Brucellosis can cause abortions in cattle and in rare cases can be passed to humans as undulant fever.
The Idaho Department of Agriculture quarantined a ranch in Swan Valley in eastern Idaho in October, department spokesman Wayne Hoffman told the Casper (Wyo.) Star Tribune.
Tests of the herd found eight cattle infected with brucellosis and two other possible infections. All 39 cows, two bulls and several calves were slaughtered.
Officials said that before the quarantine, six animals were sold through livestock markets. They were tracked and one that had gone to a small feedlot was found to be infected with brucellosis. It was slaughtered along with 16 other cattle at the feedlot.
If officials with the U.S. Department of Agriculture decide the feedlot is a second infected herd, then the state would lose its brucellosis-free status, which Idaho has had since 1991. That would require an intensive surveillance program that includes testing for brucellosis when cattle change ownership.
"We haven't heard from USDA whether that will qualify as a second herd," said John Chatburn, Idaho's deputy administrator for animal industries. "We think the heifer should be counted as one of the first herd."
The infected cattle in the Swan Valley area were on private property and had no fence line contact with other cattle herds, Chatburn said. But officials chose to test an additional 1,000 cattle in the area. None was found with brucellosis.
Chatburn said more tests are planned on other cattle in eastern Idaho, including areas where cattle have contact with elk during the winter. Three years ago, an Idaho cattle herd was found to be infected, which officials attributed to elk that had migrated from Yellowstone National Park.
"All of the epidemiological and laboratory information clearly indicates that brucellosis-infected elk transmitted the disease to the cattle herd," Chatburn said.
The Idaho Legislature recently banned the private feeding of big game animals in areas of eastern Idaho where there is a risk of elk transmitting brucellosis to cattle.
Idaho traps elk in eastern Idaho, tests them for brucellosis, and destroys infected animals. Elk that test negative are moved to new areas in an attempt to establish elk herds on other winter ranges, according to a report from the Greater Yellowstone Interagency Brucellosis Committee.