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MDARD Announces Detection of Bovine Tuberculosis-Positive Herds in Iosco County

LANSING, Mich.—The Michigan Department of Agriculture and Rural Development (MDARD) is reporting cases of bovine tuberculosis (TB) in two cattle herds from Iosco County. One herd was found as part of a trace investigation related to a previously identified TB-positive herd and the other was identified as part of routine whole herd surveillance testing.

"These latest detections of bovine TB underscore why this disease is so challenging to address and the critical need to thoroughly investigate animal movements and maintain active surveillance in order to manage this disease," said State Veterinarian Nora Wineland, DVM, MS, DACVPM. "MDARD remains committed to working together with agency partners, producers, and stakeholders to ensure the strength of Michigan's cattle industry as well as to protect animal and public health."

Bovine TB is a bacterial disease that can affect all mammals, including humans. It is known to be present in the free-ranging white-tailed deer population in specific areas of northeastern lower Michigan, and the disease can be transmitted between deer and cattle. There are currently two TB zones within the state: a four-county area (Alcona, Alpena, Montmorency, and Oscoda counties) known as the Modified Accredited Zone (MAZ) and the remainder of the state is referred to as the Accredited Free Zone.

In the past, bovine TB-infected wild deer have been found within Iosco County, and a TB-infected cattle herd was identified in May 2026. Epidemiological investigations are already underway to identify any potential additional cases stemming from these newly identified affected herds. Whole genome sequencing will also occur to help determine the source of the infection.

While MDARD and other state and federal agencies are taking significant steps to manage bovine TB within the Modified Accredited Zone through routine surveillance testing of cattle herds, mandatory animal identification, required movement certificates, and wildlife biosecurity programs, deer hunting in the northeastern Lower Peninsula continues to be an important tool in combatting this disease and maintaining healthy deer, healthy cattle, and healthy people.

More information about bovine TB can be found on MDARD's website.

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