Brucellosis can cause pregnant cattle to prematurely abort their young. It's been largely eradicated in the U.S. but persists in wildlife from the Yellowstone region of Montana, Idaho and Wyoming.
The last time Montana had two herd infections within a short period, in 2007 and 2008, it triggered federal sanctions that hampered livestock exports and harmed the reputation of the state's billion-dollar cattle industry.
Although those rules have since been eased, the recent back-to-back infections illustrate that brucellosis remains an active problem in the Yellowstone area. And industry representatives elsewhere are paying attention: Texas last month adopted a new rule requiring additional brucellosis testing of breeding cattle imported from the Yellowstone area.
Yet Zaluski said Texas's rule is unwarranted. He points out that more aggressive testing was put in place after the state temporarily lost its brucellosis-free status in 2008.
With frequent testing, cattle producers can catch the disease soon after it's transmitted to cattle from wildlife such as elk, which in turn protects against infections spreading unchecked within livestock herds, Zaluski said.
All of the animals that were infected had received vaccinations. While the vaccinations don't protect animals from initial exposure, they can prevent miscarriages that serve to spread brucellosis when other animals come into contact with an aborted fetus.
"We've succeeded in limiting transmissions with a herd, but unfortunately you aren't able to entirely prevent infections," he said.
The infected bull from Park County was killed Sept. 23 so tissue samples could be taken after a positive field test. Brucellosis tests on animals from adjacent herds are underway in Madison and Park counties.
The new testing rules in Texas came partially in response to a brucellosis case that occurred there in 2011. State Veterinarian Dee Ellis said in announcing the rules that Texas "must remain vigilant in monitoring for new incursions of brucellosis and protecting the state's agriculture industry from possible threats."
The number of cattle exported from the three Yellowstone states to Texas is relatively small. Montana, for example, exports only about 6,000 breeding cattle to Texas annually.
But Zaluski said the Texas rule could set a precedent for other states because it discredits efforts by Montana ranchers and animal health authorities to effectively manage the disease.