Wyoming’s state veterinarian said Thursday he is worried that positive tests indicating brucellosis in two young adult cows from Sublette County will prove that the  bacteria has indeed infected stock there.

The cows were first tested at a sale barn, and blood samples forwarded to a state lab in Laramie for more investigation, state veterinarian Walter Cook said in a telephone interview from Cheyenne. Each sample from the cows, which came from a Daniel-area ranch, underwent six more tests, Cook said.

“All six of those came up positive,” Cook said. “I’m pretty sure we are dealing with actual brucellosis.”

Brucellosis causes cattle to abort and is the source of undulant fever in humans, usually contracted from unpasteurized milk and soft cheeses. The Department of Agriculture, which declared all 50 states brucellosis-free for the first time in February, has targeted the disease for decades.

Montana has since lost its brucellosis-free status, which means cattle exporters must test their stock, a process one expert said would cost producers $5 million a year. Idaho and Wyoming lost, then regained, their free status in recent years after cattle herds in those states were infected by elk.

Wyoming would not lose its free status unless another infected herd is discovered within the next two years, Cook said.

During Wyoming’s recent fight against the disease, two herds in Jackson Hole were found infected and were largely destroyed. Ranchers were compensated by the federal government. Wyoming became brucellosis-free again in September 2006.

Cook said the two cows in question have been killed and necropsied. It could take a week or two to confirm that the animals are infected, a determination that can only be made by examining organ tissue. The initial blood tests only indicate exposure to the brucellosis bacteria.

An agent of the federal Animal and Plant Health Inspection Service is in Sublette County investigating, Cook said.

“We’re in the process of testing the rest of the herd,” he said. “We’re trying to determine who the contact herds might be.”

Parts of infected herds are routinely destroyed when brucellosis is found. Contact herds — those that share a fence line with an infected herd — are tested as part of the protocol of arresting the spread of brucellosis.

What will happen next is uncertain, Cook said.

“There’s a lot of concern, mixed opinion, about what to do,” he said.

A meeting for stockmen is scheduled from 7 to 9 p.m. on Tuesday at the Pinedale library.

Cook would not initially release the name of the rancher, as allowed by Wyoming law. He said privacy would protect the stockman from harassment from reporters and others.

The cattle were vaccinated against brucellosis as calves, Cook said.

“I don’t think he did anything wrong,” Cook said of the stockman.

Approximately 300 breeding animals are in the rancher’s herd, Cook said.

In Montana, loss of brucellosis-free status came with the discovery of two infected herds within two years. The result will cost stockmen a $15 testing fee for each animal 18 months or older that is sent to market, according to Myles Watts, a livestock economist at Montana State University, writing on Cattlenetwork.com. He said with a quarter-million animals going to market, the cost would be in the $5 million range.