The Prairie Star: Montana Ag Newspaper

Elk are believed to be the cause of brucellosis to recent cows found positive in Montana and Wyoming, but it is not proven. This photo is from the National Elk Refuge in Jackson. Photo by Mark Gocke, Wyoming Game and Fish Department.

HELENA, Mont. - Three cows in areas surrounding the Yellowstone National Park tested positive for brucellosis earlier this month, one, costing the state of Montana its brucellosis-class free status and two other cows, putting Wyoming on probation.

Montana's livestock industry will lose its brucellosis class-free status in three to seven weeks after a Corriente cow in Paradise Valley tested positive for the disease.

Two Angus cows tested positive last week for brucellosis in Wyoming's Sublette County, causing concern as the state regained its class-free status in September 2006. Wyoming will maintain its class-free status so long the disease isn't diagnosed in another herd within two years.

Testing performed at the National Animal Disease Center in Ames, Iowa, confirmed the presence of the brucella abortus bacterium, the causative agent of brucellosis, in the suspect cow in Montana, according to Montana Department of Livestock officials.

The state lab in Wyoming diagnosed the two Angus cows with brucellosis after blood samples were taken at an auction market, said Jim Logan, Wyoming assistant state veterinarian of Riverton, Wyo. “The lab ran all the tests for brucellosis and the cows were hot on all of them,” said Logan. “There is no doubt these cows have brucellosis.”

The Montana cow, found in a Pray, Mont., herd had been tested as a regular part of producer-initiated herd plans, implemented to provide enhanced disease surveillance due to an elevated risk of transmission of brucellosis from elk to cattle in the area, said Marty Zaluski, Montana state veterinarian. The individualized herd plans call for increased vaccination, testing and surveillance of elk.

The brucellosis-positive cow had been vaccinated for brucellosis twice, and the rest of the herd tested negative for the disease, said Zaluski, who admitted feeling frustrated by the loss of the state's brucellosis class-free status.

“Montana has been following the Interagency Bison Management Plan,” he said. “Producers in the Paradise Valley have been involved and diligent, and they have taken it upon themselves to be proactive in regard to managing the risk of brucellosis transmission. In this particular case, the owner did everything right.”

This marks the second brucellosis discovery in Montana in 13 months. The first case was diagnosed in May 2007 in a herd near Bridger, Mont., and two herds totaling 301 cows and 284 calves were depopulated to maintain the state's class-free status.

Per USDA Animal and Plant Health Inspection Service rules, the state may have only one positive herd in any two-year period to remain its brucellosis class-free status and would have had to remain brucellosis-free until July 2009 to maintain its class-free status. Montana had been brucellosis-free since 1985.

Montana may reapply for class-free status on May 27, 2009, when APHIS will conduct a review to restore the state's class free status.

As a result of the downgrade from class-free to Class A status, Montana producers will be required to test bulls and non-spayed females of 18 months of age or older 30 days prior to interstate movement and fulfill any additional restrictions as imposed by other states, said Zaluski.

Herds with links to the infected herd will be placed under quarantine unless or until they are whole-herd tested. Federal indemnity funds are available for depopulation should it become necessary, said Zaluski.

In the past 13 months, Montana has found two brucellosis cases in two Corriente cows, causing concern as to the breed's susceptibility to the disease. However, Logan said he does not believe the breed of cattle has anything to do with transmission of the disease.

“I have not seen any one breed be more susceptible to the disease than others,” he said. “If there is one, I am not aware of it. We have found brucellosis in all kinds of cattle breeds - Hereford, Angus and Corrientes, as well as others.”

As a result of the recent brucellosis discovery, Wyoming will maintain its class-free status and continue to implement best management practices for brucellosis prevention and individual herd plans in areas of concern, said Logan.

“We have risk areas or areas of concern that include all of Teton and Sublette counties, parts of Fremont County and the majority of Lincoln County,” he explained. “Park County is not included in these areas but it may be soon because of the infected elk in the county.”

While the individual herd plans and the best management practices are voluntary, Logan said producers who choose not to follow a plan are required to test their cattle prior to moving them outside the risk areas.

“We do a risk assessment for each plan,” he explained. “Some of the ranchers have to test their cattle as part of the plan and some don't. The bottom line is there is no guarantee their cattle won't get brucellosis, it is just a prevention plan.”

Losing the state's class-free status cost the “Wyoming government a couple million dollars and the producers' expenses were considerably higher,” said Logan.

While elk is suspected to be the cause of transmission to Montana cattle, there is no documented proof, according to state officials.

However, in Wyoming, there is documented proof that infected elk have transmitted the disease to Wyoming cattle in the past, said Logan.

“Most of our cases have been proven to be caused by elk,” he said. “However, the cause of this new case has not yet been determined.”

Wyoming's Fish and Game Service has 22 elk feeding grounds and Wyoming is home to the National Elk Refuge. The department uses best management plans to mitigate brucellosis transmission, said Logan. “They can vaccinate the elk, but to do that the elk need to congregate,” he said. “It is not as easy as it sounds.”