The Montana Department of Livestock (MDOL) is conducting cattle testing related to the diagnosis of bovine tuberculosis (TB) in animals during routine inspection conducted at out-of-state slaughter establishments.

These investigations, involving several states, stem from the detection of TB in a steer at slaughter in June of 2018, a second unrelated steer found in December of 2018, and a cow in March of 2019. The purpose of the traceback investigations is to determine where an animal was infected, if possible, and to identify other potentially infected or exposed animals.

Tuberculosis testing is required in a herd when a link has been established between the herd and a positive animal through movement and/or sale records. At this time, no infected herds have been confirmed within Montana. Testing is expected to continue through the summer and into early fall of 2019.

“Slaughter surveillance is a critical component of our national TB surveillance program,” said State Veterinarian Marty Zaluski. “Subsequent follow-up herd testing is necessary to ensure we find and eliminate any potential pockets of disease to protect Montana’s livestock producers.”

Bovine TB is caused by the bacteria Mycobacterium bovis. The disease causes granulomatous lesions inside the lymph nodes, lungs, liver, spleen, and skin of affected animals. The primary route of spread is aerosol transmission to other animals in close contact. The bacteria is also capable of infecting wildlife, such as deer, and people. The disease has an incubation period that can range from months to years and infected animals may show no clinical signs until later stages of infection, meaning healthy appearing cattle may be infected with the bacteria. Although TB is a zoonotic disease capable of infecting people, it is not a food safety threat, thanks to a robust meat inspection program and the pasteurization of milk for retail sale.