Wyoming Livestock Board officials have quarantined a third Park County herd after tests on four cows indicated they may have brucellosis.

After a cow tested positive at a Montana livestock market in mid-February, veterinarians tested 567 cattle in the herd the cow came from, according to a release from the state livestock board. Four cows that tested positive for exposure to the bacterial disease were removed from the herd for more epidemiological tests.

Assistant State Veterinarian Bob Meyer says the latest herd is in the vicinity of the other two quarantined herds, and infected elk are the suspected cause in all three cases.

Late last year, a herd of cattle and a herd of bison in the Meeteetse area were placed under quarantine after brucellosis was found in some of their animals.

Brucellosis is bacterial disease that can cause pregnant cattle, bison and elk to abort and can cause undulant fever in people. Areas of Park County west of Wyo. 120 lie in a designated surveillance area that requires livestock producers to hire veterinarians to test most female cattle of reproductive age for brucellosis before they are moved from the designated area. State officials have proposed placing all of Park County in the designated area. That type of brucellosis rules change would require a public comment period. Part or all of Teton, Lincoln and Sublette counties are also in the designated surveillance area.

Brucellosis has been eliminated in livestock in the United States except in areas surrounding Yellowstone National Park.

Wyoming law requires all cattle to be vaccinated against brucellosis, but existing vaccines are effective only 60 to 70 percent of the time, Meyer told the Tribune.

At a meeting in Cody on Feb. 10, area livestock producers and state wildlife officials said the disease seems to have become more prevalent, although state vets said Wyoming isn’t in danger of losing its current brucellosis-free status as long as officials move quickly to contain infections. Interim rules approved by the Animal and Plant Health Inspection Service of the United States Department of Agriculture no longer require slaughter of an entire herd when some animals test positive.