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Report assesses brucellosis in GYA

by Wyoming Livestock Roundup

On May 31, the National Academies of Sciences, Engineering and Medicine hosted an online presentation summarizing the release of their new report, Revisiting Brucellosis in the Greater Yellowstone Area.

“The report committee was tasked with conducting a comprehensive scientific literature review on the prevalence and spread of Brucella abortus in the Greater Yellowstone Area (GYA) and to evaluate the feasibility, timeframe and cost effectiveness of options to contain or suppress brucellosis,” said Committee Chair Terry McElwain.


Since their 1998 report, McElwain noted there have been many advances in the knowledge base surrounding brucellosis, as well as changes to management.

One of the major changes he stressed was a dramatic increase of brucellosis infection spilling over into domestic cattle and bison, with 27 cases recorded since 1998.

“It’s a very significant increase and is a cause of alarm. This increase was really the impetus, in large part, for taking a renewed look at the problem since the 1998 report,” said McElwain.

Another significant change since 1998 was recognition that the major transmitters of brucellosis to domestic cattle and bison are elk, rather than bison.

“Those two factors are probably the most significant piece, we think, that drove the deliberations, conclusions and recommendations that we came to in this report,” he commented.


While creating their report, McElwain stressed that the committee concluded that no single management approach could independently reduce risk to a level that would prevent disease transmission.

“There are no silver bullets. Multiple complementary strategies over a long period of time will be necessary to address the problem,” he said.

In looking at the data, McElwain suggested that reducing elk group sizes or density may decrease elk seroprevalence over time, which could potentially decrease the risk of elk transmission.

While evidence suggests the presence of a self-sustaining reservoir of brucellosis in elk without feedground contact, the committee commented that reducing use of feedgrounds may reduce overall prevalence of brucellosis in elk herds.

According to McElwain, lack of uniform wildlife surveillance outside of the designated surveillance area (DSA), as well as lack of focus on the GYA by national surveillance efforts and poor communication between state and federal agencies, are critical shortcomings to address.

“These have created an increased risk for spread of brucellosis in cattle and domestic bison outside of the DSA boundaries and beyond the GYA,” he said.


“We focused attention to a much more active degree on adaptive management in this report than the 1998 report,” said McElwain.

In one of their recommendations, the report committee advised federal and state agencies use an active adaptive approach in making timely and data-based decisions, including hypothesis testing and mandated periodic scientific assessments.

“The management actions should include multiple complementary strategies over a long period of time and should set goals showing incremental progress toward reducing risk of transmission from and among elk,” he continued.

The committee also recommended the use of supplemental feedgrounds be gradually reduced in a strategic and step-wise manner.

As a fundamental disease control method, McElwain suggested management strategies also implement spatial and temporal separation of domestic livestock from infected wildlife, which may be particularly challenging with elk.

“The options include, among others which are discussed in much more detail in the report, the timing and use of grazing allotments, biosecurity measures and hazing of elk,” he commented. “It’s important that a more science-based approach in grazing allotment use be taken to reduce the risk,” noting that knowledge gaps need to be filled before strict guidelines are implemented by agencies.

In response to an increased risk of brucellosis transmission and spread beyond the GYA, McElwain explained they advised changes be made to establish an elk surveillance program, as well as uniform, risk-based standards for expanding DSA boundaries and a national surveillance plan.

“We advise the use of multiple concentric DSA zones with different management, biosecurity, testing and movement requirements be considered based on differing levels of risk, similar to current disease outbreak response approaches,” continued McElwain.


McElwain explained that coordinated efforts will need to be made in managing the complexity of the Greater Yellowstone ecosystem.

“It will require coordination and cooperation from multiple stakeholders and will require expertise across many disciplines to understand the intended and unintended costs and benefits of actions,” he said.

He continued to explain that the action plan will also require cooperation across federal, state and tribal jurisdictions to be successful.

“We must recognize firstly that Brucella abortus in wildlife spreads without regard to political boundaries, and secondly, the current spread of brucellosis will have serious future implications if it moves outside of the GYA,” McElwain stressed.

He concludes, “Affecting this is dependent on political will, a respected leader who can guide the process with goals, timelines, measured outcomes and importantly, a sufficient budget for quantifiable success. Sharing information among those stakeholders is critical.”

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at

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