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Bovine tuberculosis investigation underway on Montana Hi-Line
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Bovine tuberculosis investigation underway on Montana Hi-Line

A rarely seen cattle disease discovered in a Montana cow at a Minnesota packing plant has prompted mass testing and quarantine in Blaine County on Montana’s Hi-Line.

The Montana Department of Livestock announced Friday that a full epidemiological investigation is underway to control the spread of the bovine tuberculosis, a disease transferable to wildlife and humans. It's been decades since bovine TB was detected in Montana. 

“We are working closely with the herd owner, United States Department of Agriculture, tribal, and wildlife officials on next steps,” said State Veterinarian Marty Zaluski in a press release. “The purpose of the investigation is to determine if other herds or wildlife are involved, and if possible, to determine the source of disease introduction.”

The beef cattle herd from which the cow originated is under quarantine. Testing is taking place on that herd and surrounding herds that may have encountered the animal during grazing or shipping.

Any ranch under quarantine won’t be able to ship cattle. This is time of year when most of Montana’s calves go to market.

What most ranchers want to know, said Veterinarian Tahnee Szymanski said whether tuberculosis will lead to other states not accepting Montana cattle, an economic haymaker for a multi-billion industry that ships most of its cattle out of state to feedlots for finishing and slaughter. Ranchers still remember a decade ago when a case of brucellosis in Montana’s herd would result in states like Nebraska refusing entry to Treasure State cattle.

The Department of Livestock’s No. 2 veterinarian, Szymanski said any restrictions in movement should be limited to herds under investigation, not the state herd as a whole. For the ranches under investigation, the burden is heavy.

“This is a tough circumstance to hand to anybody, as far as having to put animals through the chute to do TB testing. With tuberculosis, the test requires two times through the chute. So, there's a fair amount of handling depending on where they are in their natural kind of management program, they may have already worked animals for the year.” Szymanski said.

For a rancher, the testing entails rounding up every animal, some in the 300-pound range, others well over a thousand pounds, running each into a chute that squeezes it into stillness so a skin test can be scratched into its tail. Three days later, each animal must be run through again to see the test results.

Positive animals must be culled and killed, while exposed animals might be placed in quarantine until they test out. U.S. Animal Plant Health and Inspection Service records show that twice since last fall herds in Michigan and South Dakota had to be “depopulated,” meaning destroyed

The U.S. Animal Plant Health and Inspection Service reports that bovine TB was once the biggest livestock killer in the country and took decades of eradication efforts to bring under control. In the early part of the 20th century bovine TB killed more farm animals than all other infectious diseases combined. 

Disease is spread by direct contact, inhalation of droplets expelled from infected lungs, and ingestion of contaminated feed or from mother to calf through milk. Infected cattle are usually asymptomatic and can live for years without detection. A skin test required at slaughter is usually how the disease is detected. 

As the investigation unfolds, state and federal wildlife officials will begin looking for tuberculosis in animals in the area. It is too soon to tell where the current tuberculosis case originated.

“By the end of the year, we'll have some surveillance data from Fish, Wildlife, and Parks, and they'll look at, at raccoons, skunks, fox, coyotes in the area. They’ll try and take advantage of deer that have been harvested in the area that are coming through check stations for (chronic wasting disease) testing,” said Szymanski. “And if we don't find it in wildlife, then they are not a contributor to this. If we do find it, then it's a question of did it start in the cattle and spread the wildlife or did it go the other direction? And those are really hard things to say.”

It's been a brutal drought year across the state of Montana with water and grass in short supply for livestock and wildlife. Biologists told Lee Montana Newspapers earlier this year that the possibility of disease spreading between livestock and wildlife was high, as animals wild and domestic gathered at the same watering holes and feeding areas.  

There have been clusters of beef cattle herds infected with bovine tuberculosis this year in Michigan, New Mexico, Wisconsin, South Dakota, and Texas. In only two cases were herds depopulated, APHIS reports. In Michigan, tuberculosis in wildlife has become hard to eradicate.



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