Brucellosis concerns create continued challenges for Big Horn Basin producers

Worland – As cattle producers interact with wildlife on grazing permits in northwest Wyoming, brucellosis continues to create concern outside of the Designated Surveillance Area (DSA). 

“Brucellois causes abortions in cattle, elk and bison and is a disease that can affect human beings,” commented UW College of Agriculture and Natural Resources Dean Frank Galey. 

Galey looked at the challenges of dealing with brucellosis in Wyoming during WESTI Ag Days on Feb. 3-4 in Worland.

“Brucellosis was eradicated from the U.S. cattle herd a number of years ago, with the exceptions of Idaho, Montana, Texas and Idaho,” he continued.

Texas sees challenges with brucellosis because of the Mexican border. 

“We have a problem in the Greater Yellowstone Area with two very large wildlife reservoirs,” he continued. “One is bison, and the other is elk. We are dealing with a bug that is difficult to work with.”

Inside brucellosis

Brucellosis is caused by bacteria that invade the cells of their host, hiding inside the cells. 

“The bacteria hides inside of cells, and it is hard for the immune system to find, detect and kill inside a body, unless this is an infection,” Galey noted. “The immune system can beat it down and then the bug comes back.”

While there are ways to treat brucellosis if it is caught early enough, the cost-prohibitive nature of antibiotics means it is not practical to treat livestock and wildlife. 

Challenges

“The other problem with brucellosis in elk is that the bacteria is listed by the federal government as a select agent,” Galey added. “We can’t study or work on it because, as soon as we isolate it, we have to take special precautions because of the federal regulations, which makes it a challenge to work with.”

Researchers are unable to conduct trials outside a strictly controlled environment, and if the bacteria are isolated, special precautions are required because of federal regulations. 

Transmission

Brucellosis is easily spread from elk to cattle following the abortion of an elk calf. 

“What does a cow do when she sees a newborn calf? She sniffs it,” Galey said. “An aborted fetus from an elk or a cow that has brucellosis has billion of organisms, and it is a massive attack on the immune system. It is difficult for the bovine to hold that off.”

When elk and cattle commingle, especially in the later stages of calving season, problems can arise, and brucellosis can easily be spread.  

Concentration of animals contributes to transmission of brucellosis.

“Bunching is a real problem,” said Galey. “Earlier data would suggest that the late season elk is the biggest hazard for elk and cattle. Before new behavior patterns, those elk would disperse and have their calves. Now, they are staying bunched up in larger groups, longer.”

Galey noted that some evidence is present suggesting wolf activity is causing elk to bunch earlier in the season and stay in larger groups longer. 

Emerging problem

In Wyoming, Galey noted that the recent history of brucellosis in cattle began in 2004, when a case was found near an elk feedground near Pinedale. 

“In that case, we had some new genetic tools that allowed us to trace that particular bacteria isolate to an elk,” he continued. “They were genetically identical.”

On the feedgrounds, brucellosis rates run between 15 and 30 percent seropositive. 

“That doesn’t mean they all have the disease, but it means that 15 to 30 percent have been exposed to it,” Galey said, noting that figure is specific to elk in feedgrounds. 

“For the most part, elk in the rest of the Greater Yellowstone Area are less than two to three percent positive for brucellosis,” he continued. 

Brucellosis was only seen around feedgrounds until 2007-09, when positive cases showed up in the Meeteetse area. 

Later cases

“Two years ago, as part of our routine surveillance, hunter-killed elk were found positive in the Bighorn Mountains,” Galey said. “We hadn’t found any positive elk before during routine state-wide surveillance.”

Two elk were found in 2012, three in 2013 and three is 2014 in Hunt Areas 39, 40 and 41. 

“We are doing lots of surveillance in elk to be sure that we are following the transmission of brucellosis. This is the first time we have found brucellosis in elk outside the DSA,” he comments. “We do have some questions still, and we are watching this situation closely.”

Biologists are still looking at where the infected animals came from.

A 1993-96 study looking at elk distribution found only north and south migrations, and no westward communication of elk was seen at that time.

“The only thing we can guess is that positive animals worked their way west, were chased here or that new migration patterns emerged,” Galey said. 

The same study found that, later in the season, elk begin to move eastward, which can cause concern for ranchers who graze on both the east and west sides of the Bighorns. 

“There is some commingling of cattle and elk in May and June,” he commented. “Dr. Jim Logan, the Wyoming state veterinarian, has been working with ranchers in the region who have agreed to voluntary herd testing. We are trying to avoid expansion of the DSA across northern Wyoming.”

As work continues on the disease, Galey noted that it will likely prove to be problematic into the future.

“Brucellosis is an interesting disease,” he added. “We will probably be back here talking about it again in the future.”

Vaccinations

Two types of vaccine are available for addressing brucellosis – Strain 19 and RB-51.

“As near as we can tell, they are fairly equivalent in their efficacy, but RB-51 is the only one we can legally use right now,” UW College of Agriculture and Natural Resources Dean Frank Galey mentions. “We are also doing a small study right now in Ames, Iowa where we are challenging RB-51. We think boostering will be important to keep the immunity up.”

No vaccine is 100 percent effective, he adds, but many good vaccines are 80 to 90 percent effective. RB-51, however is only around 60 percent. 

“It is hard to stop the onslaught of disease when we are dealing with such a huge dose of the bacteria,” Galey said. “We are trying to find a better vaccine, but trying to vaccinate against a bug inside a cell is tough.”

Saige Albert is managing editor of the Wyoming livestock Roundup and can be reached at saige@wylr.net.