BILLINGS, Mont. (AP) — The animal disease brucellosis is emerging in new "hot spots" around Yellowstone National Park, according to new research that could complicate efforts to control transmissions of the disease to cattle.
Feeding grounds where food is left for elk as well as herds of bison inside the park have long been considered the main sources of brucellosis, which causes pregnant animals to abort their young.
But Paul Cross with the U.S. Geological Survey said a third source is now emerging: Blood tests indicate large elk herds living far from the feeding grounds have brucellosis exposure rates ranging from 10 percent to 30 percent.
That means containing the park's bison and getting rid of the feeding grounds might not be enough to stop brucellosis transmissions to cattle in Idaho, Montana and Wyoming.
The Yellowstone region has an estimated 100,000 elk and is the nation's last reservoir for the disease. Over the last decade, cattle infections have appeared in all three states bordering the park.
"It's no longer appropriate to say bison and the supplemental feed grounds are the only sources of contamination," Cross said.
Cross was the lead author of a USGS study published online Friday by the Public Library of Science.
Co-authored by researchers from Wyoming Game and Fish, Montana State University and USGS, the study was based on more than 6,000 blood tests collected from Wyoming elk between 1991 and 2009.
Since the testing began, Cross said disease rates increased dramatically in two "hot spots" — north of Dubois, Wyo. and northwest of Cody, Wyo. Both of those areas are far from the state's 23 artificial feeding grounds.
The study comes on the heels of another USGS report in March that found brucellosis rates on the rise across the region. Prevalence rates increased from between 0 percent and 7 percent in 1991-1992, to between 8 percent and 20 percent in 2006-2007.
Wyoming's feeding grounds were established decades ago to keep elk separate from cattle in the winter. By providing elk with a guaranteed food source, it was hoped they would not eat hay left out for cattle.
But the feeding grounds also facilitated the spread of disease.
Montana does not allow feeding grounds. Yet state veterinarian Marty Zaluski said the same problems result when large elk herds congregate on private lands off-limits to hunters.
Zaluski compared the trend with colds and other viruses that spread quickly through facilities such as day-care centers.
"You put any animals in close concentration, you're going to exacerbate these disease issues," he said.
Representatives of the cattle industry — backed by members of the Montana Legislature — have pushed for the state Livestock Department to take more control over elk management.
They argue that would be the only way to stem infections that can result in severe restrictions against out-of-state cattle exports.
Livestock officials so far have declined the calls to intervene, saying elk fall under the jurisdiction of Montana Fish Wildlife and Parks.
In Wyoming, wildlife managers have driven down brucellosis rates for elk in some areas through a pilot program to capture, test and kill disease-positive animals at three feeding grounds.
Where those efforts were successful, brucellosis exposure rates have dropped as low as 5 percent. That's versus 35 percent or more historically, said Brandon Scurlock with Wyoming Game and Fish.
Expanding the program across the region would carry a steep price tag.
The five-year pilot effort cost $1.3 million and removed 197 brucellosis-positive elk. That comes out to about $6,600 per animal.