Idaho continues fight against brucellosis

Jun 25, 2010

Rigby, ID, rancher Keith Lewis maintains a herd of cattle under quarantine after a cow in it tested positive late last year for brucellosis, an infectious bacterial disease that causes cattle, elk and bison to spontaneously abort their calves.

Since late November, seven cows in Lewis’ herd northeast of Idaho Falls have tested positive for brucellosis. Each of the infected animals has been removed from the herd. A test in May reportedly yielded no positive results for the rest of the herd.

Lewis’ herd is unlikely to spread the disease to other livestock because the fenced area where it is is separated from any other range pastures, Idaho Department of Agriculture state veterinarian Bill Barton said.

USDA’s Animal and Plant Health Inspection Service, which oversees livestock diseases, also has been involved in the investigation to detect if the infection has spread to other herds.

Brucellosis can cause infertility, decreased milk production, retained placentas and weight loss in cattle, elk, deer and bison, in addition to spontaneous abortions.

A controversy continues as to whether bison and/or elk that wander outside Yellowstone National Park’s borders infect domestic cattle with brucellosis, which is emerging in new “hot spots” around Yellowstone.

Barton said winter feed grounds may be propagating the disease because population poses the last remaining risk of brucellosis transmission to livestock.

Yellowstone National Park rangers have started to herd dozens of bison that have spent the spring in Montana back into the park to allow for cattle brought to area ranches. The bison are barred from Montana for much of the year under a federal/state agreement.

Bison that wander outside the park are subject to being hazed, slaughtered or shot.

Montana State District Court Judge John C. Brown on May 28 rejected an attempt by the Montana Stock Grower’s Association (MSGA) and two ranchers to require the Montana Department of Livestock to haze, harass and slaughter all bison that cross the Yellowstone boundary into the Horse Butte area, even though no cattle graze there.

The 2008 lawsuit was filed by rancher Bill Myers; Sitz Angus Ranch, located in Dillon, MT, near Yellowstone; and MSGA, which represents nearly 2,500 members.

Brown ruled the stockgrowers association and the other two petitioners do not have the legal right to require these actions under the Interagency Bison Management Plan, which is an agreement among four federal agencies and one state agency.

Represented by Earthjustice (a public interest environmental law firm), eight Horse Butte landowners and residents, the Greater Yellowstone Coalition and the Natural Resources Defense Council intervened in the lawsuit to prevent the assault on Yellowstone bison.

The University of Idaho College of Natural Resources says there are “no documented cases” of brucellosis transmitted from wildlife to cattle in natural settings.

MSGA has demanded that bison not be allowed, even on cattle-free private and public lands in Montana. Bison are the only native wildlife still confined to the park’s political boundaries of the park.

Meanwhile, three slaughter cattle exported from British Columbia (B.C.) that led U.S. officials to recently put new limits on B.C. breeding cattle may not have had brucellosis in the first place. The Canadian Food Inspection Agency (CFIA) said it has removed quarantines from the two B.C. farms where the three animals lived after its own investigation “did not confirm the presence of brucellosis.”

USDA on May 28 put temporary import restrictions on “all sexually intact” cattle and bison that have lived in B.C. since March 25 after the three animals tested as “reactors” to the disease during routine slaughter testing south of the Canadian border. Animals in that category must now test negative for brucellosis, with certification by CFIA, before they can be exported to the U.S.

USDA’s requirement did not apply to steers, spayed heifers or bison exported for immediate slaughter. However, CFIA said animals on both B.C. farms have since been tested for brucellosis, “all with negative results.”

CFIA also analyzed US- DA’s original samples from the three cattle using “more specific” tests at its World Organization for Animal Health reference laboratory in Ottawa. CFIA officials said the original suspicious test reactions observed in the U.S. lab “appear to have been caused by another bacterium that is known to create falsepositive test results.”

Canada hasn’t had a case of brucellosis in cattle since 1989. As of March 1, all U.S. states were classified as free of the disease. While Idaho confirmed infection in the Rigby herd late last year, it has kept its brucellosis-free classification. Sanitary practices in slaughterhouses and milk pasteurization prevent nearly all human cases of brucellosis, CFIA said.

Idaho National Laboratory is the only major U.S. lab testing for DNA infected with brucellosis. Its program is co-sponsored by USDA and the Department of Homeland Security. —Mark Mendiola, WLJ Correspondent