Wichita ? Animal health authorities have found no cases of tuberculosis in the Kansas dairy herd after testing more than 75,000 animals and slaughtering 18 cows that initially tested positive, the state’s top veterinarian said Monday.

The massive testing program began in April after animals from infected herds in New Mexico and Arizona were traced to dairies in southwest Kansas.

“We have the best situation possible in this scenario: complete the first round of testing and find nothing,” Kevin Varner, chief veterinarian in charge of the U.S. Department of Agriculture in Kansas.

People can catch TB, which attacks the lungs, by drinking raw milk from infected cows, but pasteurization kills the bacterium. People who milk cows or work around infected animals also are at risk.

The Kansas cattle herd has been tuberculosis-free since 1995. Had the state lost its TB-free designation, dairy or beef cattle moving out of state would have to be tested for tuberculosis, a process that takes three days.

“It is very expensive if we find TB in a state,” Varner said. “Movement restrictions go into play that affects everyone in the state. … The main effect is increased testing that can measure in the millions of dollars by the time you look at the amount of movement out; even feedlots are affected.”

The USDA bought 18 animals after initial skin tests had shown strong positive results. All those cows cleared two subsequent tests after being butchered. A final culture test on those 18 animals will take six weeks to come in, but it is not expected to turn up anything, Varner said.

Initial skin tests turned up weak positive results in 150 to 200 dairy animals, which will be retested in mid-June. Animals that test positive again will be slaughtered.