LANDER -- Two cows in Sublette County likely have been infected with brucellosis, state officials said Thursday.

The discovery, which comes less than two years since Wyoming's cattle industry was declared "brucellosis-free," raises the possibility that it could lose that status again -- if the disease is found in another cattle herd within two years.

The positive blood tests have so far been isolated to two black Angus cows from the same herd near Daniel, officials said.

Blood tests are not a fool-proof method for determining whether animals are infected with brucellosis, but blood samples from these particular cows were put through a battery of six diagnostic tests apiece, all of which produced "strong" positive reactions. That indicates a high probability the animals were indeed infected with the disease, said State Veterinarian Walt Cook.

The cattle were slaughtered, and tissues from the animals are in the process of being analyzed at the Wyoming State Veterinary Laboratory in Laramie to confirm the blood tests, Cook said. It could take two weeks or more before the final results are available.

Montana is expected to lose its brucellosis-free status in the coming days after a cow there tested positive for exposure to the bacterial disease, the second case in that state in just over a year.

The bacterial infection can cause animals such as bison, elk, cattle and swine to abort their fetuses. It can also cause undulant fever in humans.

The U.S. Department of Agriculture announced in February that for the first time in the 74-year history of the nation's brucellosis program, all 50 states, Puerto Rico and the Virgin Islands had simultaneously achieved brucellosis-free status, with Texas being the last to achieve it.

Now Montana is set to lose its brucellosis-free status, and Wyoming is one positive test away from doing the same.

Wyoming law precludes state officials from releasing the names of individual ranchers whose cattle test positive for brucellosis, Cook said. Once the state has confirmed the animals were infected with the disease, the Daniel rancher will likely slaughter all of his remaining breeding cattle.

"He'll be asked to make some tough decisions," Cook said. "No one can force him to depopulate the herd, but if he does not, it could result in the state losing its class-free status."

Wyoming lost its brucellosis-free status in 2004 after cattle herds in Sublette County and Teton County tested positive for the disease. The state regained its status in September 2006.

If the Sublette County herd proves to be infected, it will not likely lead to increased testing statewide, because the Cowboy State already has a rigorous testing program in place in the wake of a 2004 outbreak of the disease, a livestock industry representative said.

Jim Magagna, executive vice president Wyoming Stock Growers Association, said the Daniel discovery is "terrible news," but it shouldn't deal too big of a blow to the cattle industry.

"If there's anything that puts it in a better light, it's as a result of our loss of status four years ago, we've got a number of mechanisms in place to deal with it this time around," Magagna said. "We've got herd plans in place, and I think we're certainly in a better position to deal with this than we were when we had our first confirmed positives in the last incident."

Officials linked the 2004 outbreaks to elk herds that are known to be infected with brucellosis. Elk and bison in the greater Yellowstone area contain the nation's last, large reservoir of the disease.

Although news like this can come as a shock, Magagna said, as long as there is a reservoir of the disease active in the greater Yellowstone area, periodic outbreaks in cattle will be unavoidable.

"It's just about inevitable that we're going to wake up very now and then to an incident like this," Magagna said. "But, at this point, this is one incident, and Wyoming is not losing its status."

Although there had been some talk about relaxing the testing requirements for Wyoming cattle, Magagna said this incident might spur state and federal officials, along with the cattle industry, to maintain current levels of testing. But it shouldn't lead to a great deal more, he said.

"It's not going to require as much of a change in how we do business as what we had to go through the first time," Magagna said.

Once the positive tests are confirmed, state and federal officials will test the remainder of the herd in question, as well as any other herds the infected cattle might have come into contact with, including those along fence lines, Cook said.

"At this point we don't know where his cattle got infected. His herd may have got it from another herd," he said.

Jim Logan, the assistant state veterinarian in Riverton, said it's impossible to know at this point how the cows contracted the brucellosis. But he said the disease will be a "constant threat" in western Wyoming as long as there is a large number of infected wildlife there.

The state is not "pointing a finger" at wildlife at this stage, Logan said.

There is currently no treatment for brucellosis, although wild animals have demonstrated the ability to develop immunity to the infection over time. Cattle are routinely given vaccines for the disease, but no thoroughly effective vaccine has yet been developed.

The two Daniel cows that tested positive to blood tests were vaccinated as calves.

Environment reporter Chris Merrill can be reached at chris.merrill@trib.com or at (307) 267-6722.