Idaho Department of Agriculture state veterinarian Bill Barton sent a memo to state animal health officials on Monday, saying that a beef cow from a newly assembled 600-head herd tested positive for brucellosis. No calves or bred females have been sold from the herd, according to Barton's memo.

The herd has been quarantined and is being tested, and epidemiologists are trying to determine the source of the infection.

Brucellosis is rarely transmitted to humans but can cause spontaneous abortions, infertility, decreased milk production and weight loss in cattle, elk, bison and other mammals.

Barton did not immediately return phone messages from The Associated Press. Idaho Department of Agriculture spokeswoman Pamela Juker referred questions to Barton. Gov. C.L. "Butch" Otter's spokesman Jon Hanian also referred calls to the Idaho Department of Agriculture.

A spokeswoman for the federal agency that oversees livestock diseases said an investigation has been launched into whether the infection has spread to other herds.

How long that investigation could take was uncertain, said Lindsay Griffin with the Agriculture Department's Animal and Plant Health Inspection Service.

The infection comes as government officials are considering softening restrictions that apply to states with brucellosis infections.

Because the disease has been eliminated nationwide except for Yellowstone National Park and surrounding counties in Idaho, Montana and Wyoming, the government has proposed turning that area into a brucellosis "hot zone."

That would shield cattle producers outside the area from costly testing requirements for any animals they ship out of state.

A public comment period on that proposal ends Friday. No timeline has been set for putting it into place, but Griffin said APHIS would keep those potential changes in mind as it deals with the Idaho case.

That could spare the newly infected cow's owner at least temporarily from being asked to slaughter the remaining animals in the herd.

"Since there are other decisions to be made, it may buy them some time," Griffin said.

Idaho was granted brucellosis-free status in 2007 after losing the status in 2006, when the disease was found in a cattle herd in Swan Valley near the Wyoming border. Wyoming lost its brucellosis-free status in 2003 when the disease was found in a herd of cattle near Pinedale but was granted it again in 2006. Montana gained brucellosis-free status in September after losing the designation in 2008.

Idaho Department of Agriculture state veterinarian Bill Barton sent a memo to state animal health officials on Monday, saying that a beef cow from a newly assembled 600-head herd tested positive for brucellosis. No calves or bred females have been sold from the herd, according to Barton's memo.

The herd has been quarantined and is being tested, and epidemiologists are trying to determine the source of the infection.

Brucellosis is rarely transmitted to humans but can cause spontaneous abortions, infertility, decreased milk production and weight loss in cattle, elk, bison and other mammals.

Barton did not immediately return phone messages from The Associated Press. Idaho Department of Agriculture spokeswoman Pamela Juker referred questions to Barton. Gov. C.L. "Butch" Otter's spokesman Jon Hanian also referred calls to the Idaho Department of Agriculture.

A spokeswoman for the federal agency that oversees livestock diseases said an investigation has been launched into whether the infection has spread to other herds.

How long that investigation could take was uncertain, said Lindsay Griffin with the Agriculture Department's Animal and Plant Health Inspection Service.

The infection comes as government officials are considering softening restrictions that apply to states with brucellosis infections.

Because the disease has been eliminated nationwide except for Yellowstone National Park and surrounding counties in Idaho, Montana and Wyoming, the government has proposed turning that area into a brucellosis "hot zone."

That would shield cattle producers outside the area from costly testing requirements for any animals they ship out of state.

A public comment period on that proposal ends Friday. No timeline has been set for putting it into place, but Griffin said APHIS would keep those potential changes in mind as it deals with the Idaho case.

That could spare the newly infected cow's owner at least temporarily from being asked to slaughter the remaining animals in the herd.

"Since there are other decisions to be made, it may buy them some time," Griffin said.

Idaho was granted brucellosis-free status in 2007 after losing the status in 2006, when the disease was found in a cattle herd in Swan Valley near the Wyoming border. Wyoming lost its brucellosis-free status in 2003 when the disease was found in a herd of cattle near Pinedale but was granted it again in 2006. Montana gained brucellosis-free status in September after losing the designation in 2008.