The Idaho State Department of Agriculture has mounted a search for 961 purebred Holstein dairy bulls that could possibly be infected with bovine tuberculosis, a contagious disease that leads to coughing, weight and production loss, appetite problems and fevers.

Imported from California over the past few years, the cattle showed no signs of the disease when they were first inspected, said Pam Juker, ISDA chief of staff. But bovine TB can lurk in cattle for years before any infection is noticeable, she said.

Hence, the cow hunt. California officials alerted both their Idaho counterparts and the U.S. Department of Agriculture that the cattle may have been exposed to the disease, ISDA announced on Tuesday. Now, Idaho officials must find any of the bulls still alive and test them to be sure, Juker said.

The whole effort could take a couple of weeks, in part because the cattle are likely scattered across the state. It's an ambitious search in a state that's been TB-free for as long as ISDA staff could recall.

"We're planning as we go because we're not sure what we will find," Juker said.

Bovine TB is spread when cattle inhale invisible droplets containing the TB bacteria that have been coughed or exhaled by an infected animal. No vaccine exists, and the only treatment is eradication of infected livestock, Juker said.

The disease can affect both humans and animals. But humans have a very low risk of contracting it, according to ISDA. It is most commonly transmitted to humans who consume raw, unpasteurized milk or raw milk products containing the bacteria; who are involved in certain slaughter processes; or who have the closest contact to live, infected cattle and might be exposed to the bacteria in the air. The disease would not work its way into the human food supply.

Most of the animals have been in the state long enough to display symptoms of the disease - ISDA will test for antibodies produced as the bovines fight their infection. But the only sure test is to slaughter questionable animals and examine their lymph nodes for TB, former state veterinarian Greg Ledbetter said.

Should any of the bulls test positive, the herds they belong to would also be tested for the disease. And should those tests reveal a serious problem, a whole herd could be slaughtered, Ledbetter said, with the owners reimbursed.

"We really want to make sure that we don't have it," Ledbetter said.

The cattle aren't the only ones being checked. Any dairies where the disease is discovered will work with their employees to get them tested for TB as well, Idaho Dairymen's Association Executive Director Bob Naerebout said.

The good news, Ledbetter said, is that no cattle have actually tested positive yet and that any results are speculative. Idaho receives "fairly frequent" notices from other states about suspect animals, he said, and ISDA and USDA veterinarians have so far been able to defend the state from outside illnesses.

"That's what their job is, is to protect Idaho's livestock," he said.

Nate Poppino may be reached at 208-735-3237 or npoppino@magicvalley.com.