Science Center Objects

Brucellosis is a nationally and internationally regulated disease of livestock with significant consequences for animal health, public health, and international trade.

In less-developed countries, brucellosis in humans is a serious recurring illness, and is one of the most economically important zoonoses globally. In cattle, the primary cause of brucellosis is Brucella abortus, a zoonotic bacterial pathogen that also affects wildlife, including bison and elk. As a result of the Brucellosis Eradication Program that began in 1934, most of the country is now free of bovine brucellosis. The Greater Yellowstone Area (GYA), where brucellosis is endemic in bison and elk, is the last known B. abortus reservoir in the United States. The GYA is home to more than 5,500 bison that are the genetic descendants of the original free-ranging bison herds that survived in the early 1900s, and home to more than 125,000 elk whose habitats are managed through interagency efforts, including the National Elk Refuge and 22 supplemental winter feedgrounds maintained in Wyoming.

Image: Bison at Yellowstone National Park

Plains bison in winter at Yellowstone National Park.(Credit: Jim Peaco, National Park Service. Public domain.)

Between April 2002 and November 2016, 22 beef cattle herds and 5 domestic bison herds were infected around the GYE. While this is a small number of domestic herds the economic consequences of quarantine, depopulation, and/or test and removal can be high for those owners. In addition, given the high rate of cattle movement around the United States, the safety of the rest of the US cattle population depends on the ability to detect and contain these cases of wildlife-livestock spillover.

With the exception of the feedgrounds, elk were previously thought to be poor hosts. However, our research has shown that many elk populations have increased over the past 50 years and there have been coincident increases in brucellosis seroprevalence. These results may have important implications for the management of brucellosis in the GYE, sifting some of the focus from bison to elk. Our current work is on those factors that drive elk connectivity and the potential spread of this disease to new regions outside the GYE.

The NOROCK research program provides science based on an interdisciplinary approach to several key aspects: estimating and modeling disease dynamics within and among wildlife species and populations, identifying areas of cattle risk, and assessing the effectiveness of different management interventions.