Tests on about 3,000 Montana cattle have turned up no additional cases of a livestock disease that showed up in a Bridger herd in May, according to state livestock officials. While some testing will continue, the results announced Wednesday offered the most definitive evidence to date that the initial brucellosis outbreak was limited to a single herd, state officials said. "We feel significant relief certainly for ourselves but also for the livestock industry in the state," said state veterinarian Marty Zaluski. The state cannot have any additional cases of brucellosis for at least two years following the original infection, or it could lose its federal disease-free status. That would force ranchers to undergo a costly vaccination program and possibly damage the reputation of Montana's cattle industry. Brucellosis causes pregnant cows to abort their calves. It has been wiped out across most of the country but persists in bison, elk and other wildlife around Yellowstone National Park. Seven cattle from a ranch in Bridger just east of the Yellowstone area tested positive for the disease in May after being shipped out of state for sale. About 350 animals from the infected herd were later slaughtered as a precaution. Since then, approximately 3,000 cattle have undergone more than 6,000 tests for the disease all of them negative, Zaluski said. The final batch of results came in this week. They were first reported by The Billings Gazette on its Web site on Wednesday. The tests were on herds adjacent to the Bridger site in Carbon County and in Park County, where some animals from the Bridger.