BILLINGS, Mont. -- Montana has lost its federal disease-free status for brucellosis, triggering mandatory testing of cattle being shipped out-of-state.

Brucellosis, which can cause female cattle to abort their young, has been found twice in Montana in the last two years near Yellowstone National Park. Eradicated elsewhere in the country, the disease persists in Yellowstone's bison, elk and other wildlife and is occasionally transmitted to cattle.

State Veterinarian Marty Zaluski said Montana must wait until May 2009 to request reinstatement of its disease-free status. That's a year after brucellosis was most recently found in a cow from a ranch near Pray.

An earlier infection on a ranch in Bridger in May 2007 was Montana's first since 1985.

Federal DNA testing points to wildlife as the source of the Pray infection. Since no bison are found in that area, Zaluski has said elk are the most likely culprit.

The testing of cattle is expected to cost ranchers in the state's billion-dollar cattle industry an estimated $6 million to $12 million. It will be required of export cattle that are capable of breeding and more than 18 months of age, at a cost of $7.50 to $12 per head.

A small number of cattle, including those being sent directly to slaughter, will be exempt from testing.

To regain its disease-free status from the U.S. Department of Agriculture, state officials plan to expand cattle vaccinations and find ways to keep cattle from interacting with wildlife.

"Everyone knew this was coming," Zaluski said. "No one is happy about losing our brucellosis-free status, but we're optimistic that, by working together, we can develop practical approaches that reduce the risks of transmitting the disease."

Meanwhile, Wyoming also is at risk of losing its disease-free status after an infection was discovered in June on a ranch near Daniel.

Officials from both states have complained that federal regulations for the disease are too rigid, and fail to account for the unique situation of brucellosis in Yellowstone's wildlife.

But in announcing Montana's loss of disease-free status, the Department of Agriculture contended the potential economic toll would be far greater -- an estimated $80 million annually -- if the disease spread to other states.