Idaho depopulates two herds

by Cat Urbigkit

Idaho animal health officials have sent two eastern Idaho beef cattle herds to slaughter due to brucellosis infections and are awaiting word from federal officials as to whether the state will lose its brucellosis-free status.

In October, the Idaho State Department of Agriculture quarantined a ranch in Bonneville County's Swan Valley after veterinary medical officers identified a possible case of brucellosis in cattle, according to ISDA spokesman Wayne Hoffman. Further testing of the herd found a total of eight brucellosis reactors and two additional suspects in the herd. Last week, all 39 cows, two bulls and a few heifer calves were sent to slaughter to end the risk of transmission.

John Chatburn, ISDA deputy administrator for Animal Industries, said that traceout from that herd found another six animals had left the herd and were sold through livestock markets. These animals were also taken to slaughter, he said.

One of the animals was a 2005 heifer calf that was a brucellosis reactor. The heifer had been placed in a small feedlot with 17 other cattle. This small bunch of cattle was depopulated as well, Chatburn said.

"We haven't heard from USDA whether that will qualify as a second herd," Chatburn said, which would lead to the state losing its brucellosis-free status, which it has had since 1991.

"We think the heifer should be counted as one of the first herd," Chatburn said.

Wyoming faced a similar situation in late 2003 and early 2004. When one Boulder-area cattle herd was found to be infected with brucellosis, subsequent traceback discovered six seropositive cows from that herd had gone to a Washakie County feedlot. The cattle on the feedlot were determined by USDA animal health officials to be Wyoming's second infected herd, leading to the decision to downgrade Wyoming's brucellosis status to class A, which requires an intensive surveillance program, including testing for brucellosis at change of ownership. After 12 months of testing without a brucellosis-positive reactor, Wyoming applied for an advancement of class status last week.

Chatburn said the Swan Valley-area cattle had been located on private property and had no fenceline contact with other cattle herds, but all the cattle in Swan Valley - over 1,000 head - were tested, with no further evidence of infection discovered.

Brucellosis is caused by the bacteria Brucella abortus, and causes infectious abortion in ungulates.

"We have a number of other herds that we are going to test," Chatburn said, pointing to eastern Idaho cattle that may have contact with elk during the winter months.

It has been three years since brucellosis was detected in an Idaho cattle herd. In that case, elk that migrated from Yellowstone National Park in the fall wintered on a Fremont County cattle ranch and according to a paper authored by then-Idaho State Veterinarian Dr. Bob Hillman, "All of the epidemiological and laboratory information clearly indicates that brucellosis-infected elk transmitted the disease to the cattle herd."

Chatburn noted that the Idaho Legislature recently enacted a law that prohibits the private feeding of big game animals in a delineated zone throughout eastern Idaho where there is a risk of disease transmission from elk to cattle.

"There have been people who privately fed elk there," Chatburn said, in addition to one elk feedground, Rainey Creek, which is operated by the Idaho Department of Fish and Game.

"That's the only feedground, supposedly, in eastern Idaho," he said.

Idaho has adopted an aggressive brucellosis-monitoring plan for its eastern Idaho elk herds. Elk are trapped, tested and moved or removed at four locations as part of that program. Elk that test positive for the disease are removed from the population. In addition, elk that test negative for the disease have been moved from the area in an attempt to establish elk herds on winter range in other areas, according to a report from the Greater Yellowstone Interagency Brucellosis Committee.

That report indicates that brucellosis is present in elk herds east of Idaho Falls and east of Soda Springs.

"The finding of seropositive elk in these areas is not surprising given the close proximity to elk feedgrounds in Wyoming and the relatively high seroprevalence for brucellosis in elk on these feedgrounds," the report stated. In addition, the report noted that data acquired from radio-collared elk "suggests that some of the elk wintering at these sites in Idaho spend the summer and fall in Yellowstone National Park, Teton National Park, or Wyoming."