The most effective way to reduce brucellosis spread is to decrease elk populations, panel says
Decreasing elk populations in the Greater Yellowstone Area may be the most effective way to reduce the spread of the disease brucellosis to domestic livestock in the Greater Yellowstone Area, a national science panel has reported.
Hunting, contraception, testing and slaughtering infected elk and the gradual phasing out of elk feedgrounds in Wyoming were ways recommended to reduce the prevalence of brucellosis in elk.
The conclusions are a few of many contained in a 209-page report released on Wednesday by the National Academies of Sciences, Engineering, and Medicine that also urged greater state, federal and landowner cooperation. The independent 11-member panel spent 16 months reviewing the science surrounding brucellosis and problems the disease creates.
Brucellosis can cause young cattle and wildlife to abort. It’s believed to be spread through contact with birthing material. The disease was first introduced to the region by cattle but now persists in wild bison in Yellowstone National Park, as well as free-roaming elk in the GYA states of Montana, Wyoming and Idaho. An eradication program 80 years ago removed brucellosis from domestic herds in the United States.
Although brucellosis in the GYA “defies both simple solutions and a perfect solution,” wrote Terry McElwain, regents professor in the Paul G. Allen School for Global Animal Health at Washington State University and chair of the committee, the scientists still offered several recommendations.
A similar report examining brucellosis was written by a panel in 1998. Since then a lot has changed and different solutions have been tried with varying success. The biggest change overall, and maybe the most important to immediately address, is the increased exposure of elk to brucellosis and transmission of the disease from elk to cattle, the report said.
Prioritizing and sharply focusing on reducing transmission from elk should be a primary concern for all entities, McElwain said in a conference call. To do that, more information is needed about how elk use the landscape, when they use certain areas and could be aided by keeping cattle off public land grazing allotments when elk are most likely to be there and the possibility of infection is highest, he added.
Lacking from the report is an economic cost-benefit analysis because there was little information to assign a monetary amount to things like the value of an elk to an outfitter versus a wildlife watcher.
Other recommendations — such as test and slaughter of wild elk — raised the hackles of area wildlife advocates.
“I’m concerned because the focus remains on keeping the bull’s-eye on wildlife,” said Glenn Hockett of the Bozeman-based Gallatin Wildlife Association.
Stephany Seay, of the Buffalo Field Campaign, agreed.
“I think the report is disastrous for wildlife,” she said. “The burden continues to fall on them. I think the simplest solution is to remove cows from the GYA.”
For cattle ranchers like Druska Kinkie and her family in the Paradise Valley north of Yellowstone, hazing elk to decrease the chance they may spread brucellosis to their cattle has become a common activity.
“Elk are really complicated because you can’t keep them under wraps,” she said. “Hazing is a constant for us. You know, the elk aren’t stupid. They really like the valley floor.”
That same issue was highlighted in the science panel’s report, which noted that greater cooperation between federal agencies like USDA-APHIS and states is needed to ensure elk don’t spread the disease beyond what are called Designated Surveillance Areas where elk are known to have been exposed to brucellosis. The DSAs encircle Yellowstone National Park.
The other problem is that elk exposure to brucellosis has grown partly because the animals are now living in larger groups, often on private lands where cattle are not a main source of income and where hunting access is tightly regulated, thereby reducing the elk harvest by hunters.
Hockett and Seay praised the panel’s proposal to slowly reduce Wyoming elk herds’ reliance on 22 feedgrounds found close to Yellowstone. The wintering areas have been sponsored by the state, as well as a federal site near Jackson, Wyoming — the National Elk Refuge.
Although the closure of feedgrounds has the potential to reduce “seeding” of new areas with infected elk, the scientists also recognized that even without the feedgrounds, “elk are able to maintain brucellosis infection within their populations.”
The panel also wrote that “anecdotal evidence suggests that feedgrounds reduce exposure of cattle to infected elk during the high-risk period of abortion or calving,” and that an unintended outcome of closing feedgrounds could be increased exposure of cattle to infected elk if cattle are turned onto grazing areas at the time that elk are calving.
“The weight of evidence nonetheless suggests that reduced use or incremental closure of feedgrounds could benefit elk health in the long-term, and could reduce the overall prevalence of brucellosis in elk on a broad population basis.”
Such proposals in the past haven’t set well with Wyoming hunting outfitters or cattle ranchers.
Developing a better vaccine to protect cattle and domestic bison, as well as a way to deliver a vaccine to wildlife like elk, was another option advocated by the scientists.
But Kinkie and Hockett agreed that a new or better vaccine seems unlikely, partly because it would be so expensive to develop.
“People put a lot of stock in vaccines, but I think it’s a pipe dream,” Kinkie said. “People have been wanting a better vaccine for 10 years and there’s been absolutely no movement,” partly because it’s on a biohazard list that limits which laboratories can handle the disease. The panelists advocated removing brucella abortus from the list to aid laboratory research.
Even though the scientists recognized the larger threat elk now play in spreading brucellosis, they did not ignore Yellowstone National Park’s continued management of wild bison that have been exposed to the disease. Yellowstone officials have been using a winter slaughter program to reduce the park’s bison population, with the side benefit of reducing the number of bison exposed to brucellosis. The park also tries to keep bison and cattle separate, aided in part by the Forest Service closure of some cattle grazing allotments west of the park.
“Removal of bison for population management purposes could target B. abortus infected individuals if further reducing the prevalence of brucellosis is a goal;” the report stated. “However, until tools become available that would simultaneously allow for an eradication program in elk, additional aggressive control measures in bison seem unwarranted.”
The report also supported quarantine of Yellowstone bison that test negative for exposure to brucellosis so they could eventually be relocated, an effort that has been endorsed by wildlife advocates and tribal representatives as a way to grow tribal herds and reduce the number of animals sent to slaughter.
Yellowstone superintendent Dan Wenk said he and his staff have not had time to review the report but said the scientists had given members of the Interagency Bison Management Plan a lot of ideas to consider and discuss. The IBMP includes representatives from state and federal agencies.
“I can’t tell you anything special that we will or will not do yet,” Wenk said. “Certainly it’s something important to all of the partners of the IBMP.”
Other options the scientists suggested for bison were studies to “preserve genetic material and live cells for future use in establishing brucellosis negative and potentially disease resistant bison through cloning techniques;” and “targeted removal” of infected or high-risk bison within Yellowstone in the winter to reduce the need for large culls, although the scientists acknowledged the “option may not be politically, logistically, socially, or economically feasible.”
The options proposed for bison management angered Seay, who’s been a constant critic of the park’s bison slaughters, calling the report a “lot of bureaucratic control as usual. We need to take a close look at the value of free-roaming wildlife in this ecosystem” in comparison to the value of more livestock on the landscape, she said.
Even if there was money to fund all of the proposals suggested by the scientific panel, their report noted that “eradication of brucellosis from the GYA remains idealistic, but is still not currently feasible for scientific, social, political, and economic reasons.”
Yet McElwain said eradication should be a long-term goal, especially in domestic livestock and bison.
To reach that goal the panel encouraged cooperation at the highest levels of state and federal government to try to address the disease before it spreads to outlying areas, possibly reversing the decades of previous eradication efforts. To do that will take a coordinated, science-based approach that so far has yet to occur.
“To date, the efforts undertaken by various state and federal entities have been conducted in a piecemeal fashion, resulting in a disjointed and uneven approach,” the panel said.
Attempts to contact officials from Montana Fish, Wildlife and Parks, Wyoming Fish and Game, the Montana state veterinarian and Montana Stockgrowers Association for comment on the report were unsuccessful.
The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine.