Elk in Crazy Mountains Test Negative for Brucellosis, Easing Livestock Concerns

In late January, Montana Fish, Wildlife and Parks conducted operations in the Crazy Mountains northwest of Big Timber, Montana, capturing elk and testing them for brucellosis. As part of an ongoing surveillance project, the team secured 52 elk, fitting 16 animals with GPS tracking collars to monitor movement patterns. While positive tests for the highly contagious disease have increased over recent years, FWP’s laboratory results from the Crazies showed all sampled elk tested negative for the disease, indicating no detected exposure in the herd.

The testing is the latest from the Targeted Elk Brucellosis Surveillance Project, a collaboration between FWP and the Department of Livestock created in 2011 to monitor and understand the spread of brucellosis among elk populations, and to correctly delineate the geographical distribution of the disease. Exposure detection in two elk near Greeley Mountain and McLeod Basin in 2016 made sampling in the Crazy Mountains a priority, as did the large presence of livestock in the area.

The negative results in the Crazy Mountains have wildlife researchers fairly confident that elk there have not been exposed to brucellosis and do not pose a disease transmission risk to livestock, providing crucial reassurance for the region’s cattle industry.

“Test data from live elk captures inform brucellosis management decisions in Montana,” State Veterinarian Tahnee Szymanski said in a February 13 press release. “These negative test results are valuable to Montana’s livestock industry as they help provide confidence to our trading partners about the quality and strength of our state program.” 

The Greater Yellowstone Ecosystem has battled the chronic presence of the infectious disease threatening wildlife and livestock since 1917, when it was first found in the region.

Historically, surveillance for the disease across the GYE largely relied on collection samples from hunter harvested animals, making it difficult to obtain large enough sample sizes from Montana elk to inform state management decisions. To fill this gap in data, the project focuses on elk herds near the boundaries of Montana's designated surveillance area — the region identified as having elk exposed to brucellosis. Since its inception, researchers have conducted targeted sampling on 24 different elk herds, with 10 of those herds testing positive for brucellosis exposure.

Jenny Jones, research technician for FWP told Mountain Journal it’s important to note that brucellosis exposure is determined by the detection of antibodies to the disease. It is possible that an animal testing positive is not actively infected—it may have cleared the disease, or it could be dormant.

Jones said researchers aim to capture around 100 elk from each herd. “If prevalence is greater than or equal to 3 percent, then by sampling 100 elk there is a 95 percent chance of finding at least one exposed animal,” she said.

The surveillance operations, primarily funded by the Animal Plant Health Inspection Service with additional support from the Rocky Mountain Elk Foundation, involve intensive field work during Montana's winter months. Each January and February, contracted helicopter teams pursue elk across snowy landscapes, netting individual animals for testing.

Helicopters allow researchers to catch approximately 25 elk per day in a short amount of time from a specific area. Once captured, the animals are blindfolded and hobbled before the researchers take blood samples and attach GPS collars to selected individuals. But because elk herds often winter on private property, the scientists need help from willing private property owners.

“Capture operations would not be possible without assistance and permission from numerous landowners,” Jones said.

The collars, typically applied to approximately 30 of the elk captured, provide critical hourly movement data that reveals migration patterns and potential transmission risks. The data serve multiple purposes beyond disease surveillance, helping biologists understand seasonal range use and informing hunting quotas and district boundaries.

The primary driver of this extensive surveillance effort is the risk of transmission from elk to cattle. Jones said she is not aware of any cases of bison spreading the disease to cattle. The  perceived threat has been a controversial focus for ranchers during ongoing wild bison management decisions.

“The main concern is elk to livestock, which is predominantly cattle with a few bison ranches as well,” Jones said. “Most cases of livestock infection have traced the initial transmission to elk.  Wild bison are not generally allowed in Montana, while elk movement is unrestricted.” 

For Montana's cattle industry, a brucellosis outbreak carries severe consequences, including extensive testing, quarantine and potential loss of livestock.

“There is no treatment for wildlife or livestock,” Jones said. “There are vaccines administered to livestock but as with all vaccines they are not 100 percent effective. Livestock that test positive are euthanized and the remaining herd is quarantined.”

The disease also poses health risks to humans, particularly dairy workers and hunters who may encounter contaminated fluids or tissues. Human brucellosis typically presents as a flu-like illness with fatigue but if left untreated can lead to long-term conditions like arthritis, recurring fever and memory loss, according to the Centers for Disease Control and Prevention.

Since 2010, when Montana created the designated surveillance area, or DSA, its boundary has been expanded five times based on surveillance results showing exposure in previously unaffected areas. These adjustments, recommended by the Department of Livestock and approved by its governing board, help maintain Montana's brucellosis-free status for interstate livestock trade while acknowledging the disease's continued presence in wildlife.

Szymanski said it’s a big lift for producers who run cattle operations in the DSA. State requirements mandate that cattle over 12-months in age that are sexually intact must have a negative brucellosis test if they leave the DSA. She said 95,000-100,000 animals are tested in Montana every year. 

“We’ve had 13 affected livestock herds since the inception of the program,” Szymanski said. “It’s not that there are a substantial number of herds affected, but the reason we do the wildlife surveillance is to know where are on the landscape seropositive elk are and where livestock would be at risk for transmission. It’s how we decide our programmatic requirements.”

Brucellosis cases in cattle are managed by each state’s Department of Livestock. Jones said that while some limited information is shared with FWP and the public, such as the county in which infection is detected, specific information is confidential. 

“Wyoming and Idaho also have their own DSAs,” Jones said. “Some of the boundaries align along the state boundaries, primarily, because brucellosis is endemic in Yellowstone National Park and likely spread from there out to all three states [of Montana, Wyoming and Idaho].”

Despite the disease's persistence, she said, wildlife management practices remain largely unchanged in affected areas, with the exception of hazers — people on horseback or ATV who elicit movement of elk herds off private property and away from cattle — deployed in Madison and Paradise Valley to move elk away from private property with livestock.

According to FWP’s website, the agency, along with informal input from the Elk Management Guidelines in Areas with Brucellosis Working Group, annually assemble a work plan outlining potential management actions within the DSA or other areas where brucellosis-exposed elk have been confirmed within the previous five years. Before implementation, these management plans must receive formal approval from the state Fish and Wildlife Commission.

Szymanski said she considers Montana’s program to be successful at mitigating the spread of brucellosis. “We are very fortunate to have the level of buy-in that we do, and a [cattle] industry that’s really engaged in the discussion.”

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