IDAHO FALLS, Idaho (AP) - Scientists at the Idaho National Engineering and Environmental Laboratory are developing a new brucellosis test that can determine whether infected bison are actually contagious.

INEEL officials say final work should be completed in a year on the test for the disease, which many Yellowstone National Park bison carry and which poses an economic threat to commercial livestock.

Because there is no way to identify the contagious animals in a herd, hundreds of bison have been sent to slaughter since 1996 in Montana simply because they tested positive for brucellosis.

"We just want to prevent the slaughter," INEEL molecular biologist Deborah Newby said.

Brucellosis is a bacterial infection found in cattle, bison, elk, sheep and goats. The strain of the disease Newby and her colleague Frank Roberto are studying causes animals to spontaneously abort fetuses and could leave animals infertile.

There has been no documented transmission of brucellosis from bison to livestock in the wild.

The disease can also be passed to humans as undulant fever through unpasteurized milk or undercooked, contaminated meat.

While not deadly, the bacteria can cause fatigue, night sweats, joint pain and fever.

Newby and Roberto have developed a system where DNA from animal tissue is tested for contagion. The results can be provided within an hour. Their next step is to make the test more portable so it can be easily used in the field.

Brucellosis was essentially eradicated from commercial livestock in Idaho in 1989, and cattlemen have been free to market their stock throughout the country. A resurgence has the industry worried because it could result in the state losing its brucellosis-free designation and stock being quarantined.

"If it got into cattle, it would be a huge problem," Caribou County Agricultural Extension Agent Steve Harrison said. "No one would allow us to bring cattle into their state or anywhere else."