Black angus cattle grazing on the range on a Montana cattle ranch

(The Center Square) – Montana recorded its first confirmed case of bovine tuberculosis in more than 50 years in a beef herd in Blaine County, the state veterinarian confirmed.

Meat inspectors discovered a single cow with bovine TB at a processing plant in Minnesota. It was traced back to the Blaine County herd, Dr. Marty Zaluski, Montana Department of Livestock veterinarian, told the Center Square.

Bovine tuberculosis is a now-rare disease of cattle that was extensive in the 1920s and ‘30s, but after an expensive and diligent eradication campaign, few cases are found in the United States, he said.

“It's more of a public health issue for dairy. That's why pasteurization is required on most milk,” Gilles Stockton, president of the Montana Cattlemen’s Association, told the Center Square.

A single cow was found with lesions during a post-mortem inspection at a Minnesota slaughter plant, he said. All cattle or their carcasses are inspected before going into the food supply. From the identification tags on the animal it was traced back to the Blaine County herd, Zaluski said.

“We conducted a whole herd test on that herd in Montana and then we found three additional animals that were confirmed with bovine tuberculosis in that herd,” Zaluski said.

The herd was categorized as affected and has been quarantined. Two options exist for the herd. The first is depopulation. The herd would be sent to slaughter and inspected. The owner will get a salvage value for the herd. The other option is to keep the animals quarantined for probably a year while they determine if any of the remaining herd members were infected. Those that remain in the clear can be declared tuberculosis negative, he said.

It’s disruptive for this Blaine County family to have cattle with tuberculosis and Zaluski said he empathizes with that situation.

Often the Department of Livestock and the USDA never know how a cow gets infected. The USDA has performed genome sequencing on the affected animal. The closest relative to the bovine tuberculosis in it was isolated in central Mexico in 2006. But they aren’t aware of any links to Mexican cattle for this animal, he said.

If the herd owner didn’t purchase the animal from neighboring cattle in adjacent herds, he probably bought a cow that had contact with Mexican cattle.

“We know that being in the cattle business is not a zero-risk endeavor and so people do make decisions based on recognizing that there is a risk,” Zaluski said.

In most cases, tuberculosis infection does not occur.

For this rancher, the effects are dramatic. The infected cattle can jeopardize the family’s whole business model, its tradition and breeding history. It’s highly disruptive economically because indemnity will not cover the entire cost to that family, he said.

Folks whose own cattle have had fence-line contact with the infected herd will face additional scrutiny.

For any family whose herds are put under quarantine, financial transactions and the ability to complete sales that are critical to stay in business are jeopardized.

“The public health or human health impacts are generally limited to consumption of raw, unpasteurized milk from infected animals,” Zaluski said.

Some documented cases exist where people were the most likely source of an infected cattle herd, he said.

Not much can be done to prevent infection as the likelihood of tuberculosis in any animal is low. The most important thing is to have complete records of the animals and conduct tests recommended by veterinarians.