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Introduction

1. BACKGROUND

Brucellosis, a zoonotic bacterial disease, was first noted in the Greater Yellowstone Area (GYA) in 1917 and has been present in the GYA since then. In 1998, the National Research Council (NRC, now referred to as the National Academies of Sciences, Engineering, and Medicine, or “the National Academies”) was asked to review the scientific knowledge regarding Brucella abortus transmission among wildlife—particularly bison and elk—and cattle in the GYA (NRC, 1998). That study considered the mechanisms of transmission, risk of infection, and vaccination strategies. It also assessed the infection rate among bison and elk and described what was known about the prevalence of B. abortus among other wildlife.

Since that study was conducted, brucellosis has re-emerged in domestic cattle and bison herds in the GYA. From 1990 to 2001, no infected domestic herds were identified. However, between April 2002 and November 2016, 22 beef cattle herds and 5 domestic bison herds were found to be infected. Brucellosis is a nationally and an internationally regulated disease, and the GYA is the last known B. abortus reservoir in the United States.

Brucellosis infection and its management have multiple consequences for the local GYA economies (related to livestock and wildlife), and it can potentially affect export of domestic livestock nationally and internationally. In cattle, B. abortus infection results in late-gestation abortion, decreased milk production, loss of fertility, and lameness. Placental infection with production of very high numbers of bacteria is the dominant pathologic manifestation associated with transmission. A similar clinical syndrome occurs in bison infected with B. abortus (Rhyan et al., 2009). In the United States, brucellosis is no longer a major human health concern (CDC, 2012). However, in less-developed countries, brucellosis in humans resulting from direct exposure to infective material and consumption of unpasteurized milk products is a serious recurring illness; it is consistently one of the most economically important zoonoses globally (McDermott et al., 2013). Brucella bacteria have been found in flies (Musca autumnalis) associated with cattle and lungworms of seals (Garner et al., 1997); however, no current evidence suggests that these are important vectors of disease transmission.

Brucellosis is endemic in bison and elk in the GYA. 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. Roughly 60% of Yellowstone bison are seropositive for Brucella (Hobbs et al., 2015). The GYA is also home to more than 125,000 elk, whose habitats are managed through interagency efforts, including the National Elk Refuge (NER) and 22 supplemental winter feedgrounds maintained in Wyoming. Seroprevalence in feedground elk ranges from about 10% to 40% (Scurlock and Edwards, 2010).

Feedgrounds reduce the seasonal loss of elk in winter, thereby increasing the elk population and changing other elk behaviors, such as those related to parturition. Comingling of elk with cattle is the cause of current brucellosis outbreaks in cattle. Although most cattle in the GYA are vaccinated with B. abortus strain RB51, it does not necessarily prevent infection but it does reduce abortions (Olsen, 2000).

B. abortus isolates recovered from infected cattle very closely resemble or are indistinguishable from isolates in wild elk. Over the past decade, seroprevalence in some elk herds increased without direct exposure to feedground elk. This finding suggests that brucellosis is now self-sustaining in free-ranging elk distant from the feedgrounds and thus accounts for increased risk to cattle. Other factors that increase the complexity in managing brucellosis and the Greater Yellowstone Ecosystem (GYE) include the 1995 reintroduction and subsequent recovery in numbers of grey wolves in Yellowstone, changes in land use, and changes in federal and state regulations. The GYA is now home to 400-450 wolves (Jimenez and Becker, 2015), which prey primarily on elk. Furthermore, the grizzly bear population has increased, with 150 having home territories in the Park itself (Yellowstone Park, 2016) and approximately 500-600 with ranges in the GYA (USFWS, 2016). These changes have led to movement of elk outside YNP and into areas where increased exposure to cattle can occur.

In 1998, bison were the primary focus of the NRC’s evaluation of brucellosis in the GYA. Since that time, the Interagency Bison Management Plan (IBMP) was implemented to achieve the spatial separation of bison and cattle, which has dramatically reduced the risk of bison transmitting B. abortus to cattle. Bison remain an important focus, but it is clearly evident that the rate of transmission from elk has increased significantly. The GYA is a complex and dynamic ecosystem that requires both a reanalysis of changed and changing factors and recommendations on strategies and goals in light of those factors.

2. THE GREATER YELLOWSTONE AREA

The GYA (see Figure 1-1) has been defined as the general area including and surrounding Yellowstone and Grand Teton National Parks, spanning about 400 km north-to-south and 200 km east-to-west (White et al., 2015). The general boundaries of the GYA were delimited by the Greater Yellowstone Coordinating Committee in 1994 (McIntyre and Ellis, 2011). The GYA consists of Yellowstone and Grand Teton National Parks as core naturalareas that are surrounded by six national forests, three national wildlife refuges, state lands, Bureau of Land Management (BLM) land parcels, and private and tribal lands (White et al., 2015). These areas are administered by many different federal and state management entities. The federal agencies responsible for overseeing those lands include the National Park Service (NPS), the U.S. Fish & Wildlife Service (USFWS), BLM—which are part of the U.S. Department of the Interior (DOI)—and the U.S. Department of Agriculture’s (USDA’s) Forest Service (USFS). The state agencies include Idaho Department of Fish and Game, Idaho State Department of Agriculture, Montana Department of Fish, Wildlife & Parks (MDFWP), Montana Department of Livestock, Wyoming Game & Fish Department (WGFD), and Wyoming Livestock Board.

2.1 Terminology

The GYA is included within an area that has been referred to as the GYE, one of the largest, mostly intact, temperate ecosystems in the world (Keiter and Boyce, 1991). The GYE was originally defined as the range of the Yellowstone grizzly bear (Craighead, 1991; Gude et al., 2006), but ecosystem boundaries are somewhat subjective and dependent on movements and interactions among many species. For the purposes of this report, the area of interest includes the GYA, but also areas in and near the GYA where brucellosis is known to occur in elk and bison and where there is a risk of transmission to domestic livestock and domestic bison herds (see Figure 1-2). Areas with brucellosis presence or risk of transmission are included in the brucellosis designated surveillance areas (DSAs) of eastern Idaho, southwest Montana, and western Wyoming.

2.2 Bison and Elk Populations

As of 2016, the GYA supports more than 5,500 bison. The great majority are found in the YNP herd, which varies in size between 3,000 and 6,000 animals. Since 1998, when the previous NRC brucellosis report was written, the YNP bison population has increased from 3,000-4,000 to 4,000-5,000. YNP bison are primarily found within the Park boundaries, but they also use areas outside of the Park to the north and west. The YNP herd consists of two subherds, central and northern, with some interchange between them. In contrast to 1998, when there were considerably more bison in the central herd than in the northern herd, there are now more bison in the northern herd. A second and much smaller herd of about 700 bison has a core range inside Grand Teton National Park (GTNP), with most wintering on the NER (Koshmrl, 2015).

There are more than 125,000 elk in the GYA. Several herds have winter ranges in and around YNP, including the northern Yellowstone winter range herd, which was, up until recently, the largest herd in the GYA. A second set of herds, the Jackson herds, have winter ranges in the southern parts of the GYA, including the USFWS NER and surrounding areas near the town of Jackson. The Jackson herd has been larger than the northern Yellowstone herd for the past two decades. Within YNP, elk have been managed by NPS under a policy of natural regulation, in which it is hypothesized that the area is large enough for populations to be regulated by food limitation or predation, without a need for artificial reductions. However, YNP elk ranges extend beyond park boundaries. Elk outside YNP are managed by state and federal wildlife management agencies. YNP provides summer range for six to seven elk herds, most of which spend the winter at lower elevations outside YNP (NPS, 2015).

3. ADMINISTRATIVE COMPLEXITY OF THE GREATER YELLOWSTONE AREA

3.1 Regulatory Authority of Various Species

Cattle, bison, and elk are managed by different state and federal agencies. For cattle, USDA’s Animal and Plant Health Inspection Service (USDA-APHIS) has regulatory oversight of livestock, with objectives to safeguard livestock health, maintain the economic viability and trade capabilities of the U.S. cattle industry, and protect public health and food safety (Clarke, 2015). USDA-APHIS has the national authority to suppress and prevent the spread of any contagious and infectious disease of livestock, which could include establishing quarantines, regulating the movement of livestock, and seizing and disposing of livestock (Clarke, 2015). Similarly, state departments of agriculture or their equivalent have regulatory oversight of livestock and are responsible for protecting producers, trading partners, and public health in their respective states.

Bison and elk move across wide ranges of land and, not surprisingly, their management crosses administrative boundaries. The NPS has jurisdiction in managing bison within Yellowstone and Grand Teton National Parks. Outside the national parks, bison are under the authority of state agencies and may be considered as either wildlife or livestock, depending on the context. In Wyoming, bison are considered wildlife in specific designated areas adjacent to Yellowstone and Grand Teton National Parks (Becker et al., 2013). In Montana, the Yellowstone bison population is considered as wildlife, with MDFWP managing hunting on lands adjacent to YNP and with the Montana Department of Livestock in charge of disease control management (Becker et al., 2013). For the purpose of brucellosis management, USDA considers all bison removed from YNP as alternate livestock (Becker et al., 2013). Only in the event of a national disease emergency would USDA-APHIS have authority over wildlife.

For elk, DOI has jurisdiction inside Yellowstone and Grand Teton National Parks, the USFS is responsible for providing habitat on national forest lands, the BLM has authority over its land parcels, and the USFWS (DOI) manages the NER. With regard to the states, the state wildlife management agencies in Idaho, Montana, and Wyoming have authority over elk population management anywhere outside of the national parks.

In addition to the state and federal agencies, there are three Native American Indian reservations in the near vicinity of the DSA: Fort Hall, Wind River, and Crow. The Fort Hall Reservation of the Shoshone-Bannock Tribes is in southeastern Idaho (over 2,000 km²). The Wind River Reservation created for the Eastern Shoshone and Northern Arapaho Tribes is approximately 9,000 km² and is located on the eastern side of the Wind River mountains in Wyoming. Wild bison were recently translocated into the Wind River Reservation in 2016. The Crow Indian Reservation for the Crow Tribe is located in Montana north of the Bighorn Mountains (9,300 km²).

3.2 Coordination and Management of Bison and Elk Among Agencies

Yellowstone elk populations migrate, disperse, and utilize habitats outside of the national parks and are managed by state wildlife authorities for recreational hunting. This means that despite any policy of natural regulation or ecosystem process management of the NPS, elk populations that spend a part of the year inside Yellowstone and Grand Teton National Parks can be and are managed by state game management agencies through hunter harvests, to varying degrees. The extent to which hunting controls elk populations relative to habitat and food limitation and winter weather inside YNP and GTNP has been insufficiently recognized or characterized. Clearly a major goal of state wildlife authorities is to produce thriving and sustainable populations of wildlife, primarily for hunting and fishing. However, state wildlife authorities also serve multiple stakeholders. For example, MDFWP manages Montana’s fish and wildlife populations and habitats while balancing the interests of groups such as hunters, outdoor recreationists, visitors, landowners, and the general public (MDFWP, 2004). Consistent with the mission of the National Wildlife Refuge System in sustaining healthy wildlife populations (USFWS and NPS, 2007), the mission of the

USFWS’s NER is to “contribute to elk and bison populations that are healthy and able to adapt to changing conditions in the environment and that are at reduced risk from the adverse effect of non-endemic diseases.”

The need for coordination among agencies in managing bison and elk led to the formation of numerous coordinated management plans such as the IBMP (2014) and the Bison and Elk Management Plan for the NER and GTNP (USFWS and NPS, 2007). It also led to numerous interagency working groups and committees, such as the Northern Yellowstone Cooperative Wildlife Working Group (which coordinates management of the northern Yellowstone elk herd) (Cross, 2013); the Jackson Interagency Habitat Initiative; and the Greater Yellowstone Interagency Brucellosis Committee (which is no longer operational). Similar GYA-scale efforts have been organized for grizzly bears (Interagency Grizzly Bear Study Team) and for wolves (Northern Rocky Mountain Wolf Recovery Program; Jimenez and Becker, 2015).

4. PURPOSE OF THIS STUDY

USDA-APHIS requested that the National Academies revisit the issue of brucellosis in the GYA. The primary motivation for USDA-APHIS was to understand the factors associated with the increased occurrence of brucellosis transmission from wildlife to livestock; the recent apparent expansion of brucellosis in non-feedground elk; and the desire to have science inform the future course of any actions used to address brucellosis in the GYA. Although USDA-APHIS commissioned the study to inform its brucellosis eradication strategy, the GYA comprises some 145,000 km², including state, federal (BLM), private, and tribal lands, as well as national parks, forests, and wildlife refuges. Each political entity has its own mission and goals, including disease management, ecosystem management, and recreational purposes. This subject is of great interest to many people of widely divergent backgrounds and experience, and public opinion also needs to be accounted for because YNP is a national icon. Therefore, a broader audience for the report is addressed apart from USDA-APHIS, including other federal agencies such as the NPS and the USFS, state and tribal governments, and the public, both nationally and locally, including hunters and ranchers with economic interests in wildlife and domestic food animals in the GYA. The Statement of Task for the study attempts to address those concerns and encompass the complexity of the issues (see Box 1-1).

5. APPROACH TO THE TASK

The National Academies convened a committee of 11 experts who collectively have extensive experience in veterinary pathology, wildlife biology, molecular immunology, vaccinology, laboratory diagnostics, brucellosis regulatory program management, disease modeling, ecology, and agricultural and natural resource economics. (See Appendix A for the committee membership and biographies.) Using the 1998 report as a launching point for the current report, the committee conducted an extensive scientific literature review to inform its current understanding of brucellosis.

The committee held three meetings as part of the information-gathering process.¹ (See Appendix B for the open session meeting agendas.) The committee solicited information from multiple sources, including the sponsor (USDA-APHIS), NPS, USFS, and the state governments of Idaho, Montana, and Wyoming. To augment its understanding of the GYA, the committee participated in a field trip through YNP hosted by the NPS. The committee also gathered information from researchers who have contributed to the scientific body of work on brucellosis. At each of these meetings, members of the public provided comments that informed the committee in addressing its task.

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¹ As part of the information-gathering process, materials submitted to the committee (presentations and written materials) by externalsources are listed in theproject’s public access file and can be madeavailable to thepublic upon requestby contacting the Public Access Records Office at paro@nas.edu.

6. ORGANIZATION OF THE REPORT

The remainder of the report is divided into three sections: an overview of the current situation and a review of new information since the previous 1998 report (Chapters 2-5); an examination of integrative adaptive management approaches and tools for addressing brucellosis (Chapters 6-8); and a look at future research needed to address brucellosis in the GYA (Chapter 9). In describing recent developments since the 1998 report, Chapter 2 examines the geographic scope of bison and elk populations across the GYA, and discusses the implications of land use changes and changing climate for bison and elk populations. Chapter 3 discusses the prevalence and epidemiology of B. abortus in the GYA. Chapter 4 provides an overview of the current scientific understanding of B. abortus and discusses how new scientific tools have been critical in contributing to the body of knowledge for understanding brucellosis transmission, pathogenesis, and risk management. The management efforts of federal, state, and regional partners are discussed in Chapter 5. Chapter 6 describes integrative adaptive management approaches to be adopted as part of a strategy for addressing brucellosis in the GYA, and Chapter 7 outlines management options for managing brucellosis. Bioeconomic analysis of wildlife diseases management has emerged as a new research area since the 1998 report, and the use of a bioeconomic framework that can address economic and social aspects of the issues (discussed in Chapter 8) will be critical for making decisions. Chapter 9 outlines some remaining research gaps to understanding and controlling brucellosis in the GYA. The last chapter of the report (Chapter 10) synthesizes the concerns and provides the committee’s overall findings, conclusions, and recommendations related to its Statement of Task.

REFERENCES

USFWS (U.S. Fish & Wildlife Service). 2016. Draft 2016 Conservation Strategy for the Grizzly Bear in the Great Yellowstone Ecosystem. Missoula, MT. Available online at https://www.fws.gov/mountain-prairie/es/grizzlyBear.php (accessed May 16, 2016).

USFWS and NPS. 2007. Bison and Elk Management Plan for the National Elk Refuge and Grand Teton National Park. Available online at http://www.fws.gov/bisonandelkplan (accessed January 4, 2017).

White, P.J., R.L. Wallen, and D.E. Hallac. 2015. Yellowstone Bison Conservingan Icon in Modern Society. Yellowstone National Park, WY: Yellowstone Association.

Yellowstone Park. 2016. Yellowstone Grizzly Bears by the Numbers. Available online at http://www.yellowstonepark.com/grizzly-bear-facts (accessed May 16, 2016).