The Michigan Department of Agriculture and Rural Development has detected bovine tuberculosis in a cattle herd in Alcona County, part of the northeastern Lower Peninsula zone where the disease persists in wild white-tailed deer.
The department announced the case Monday in a news release. The herd was identified through routine annual whole-herd surveillance testing in the state's Modified Accredited Zone, a four-county area made up of Alcona, Alpena, Montmorency and Oscoda counties. The rest of Michigan is classified as the Accredited Free Zone. The department did not disclose the size or type of the herd.
Bovine TB is a bacterial disease that can affect all mammals, including humans. In Michigan, it is known to be present in free-ranging white-tailed deer in specific areas of the northeastern Lower Peninsula, and it can pass between deer and cattle.
The next steps are investigative. MDARD has opened an epidemiological investigation to identify any additional cases tied to the herd, and whole genome sequencing will be used to help determine the source of the infection.
State Veterinarian Nora Wineland said the detection shows why herd testing continues in the zone.
"Bovine TB is a persistent, complex disease, which is why routine surveillance testing remains an essential disease management tool. Every test helps us to determine where bovine TB is and to improve our understanding of how it might be shifting across Michigan's landscape, improving our capacity to respond to this disease," Wineland said.
Cattle producers in the zone operate under several layers of control. The state relies on routine surveillance testing of cattle herds, mandatory animal identification, required movement certificates and wildlife biosecurity programs, according to the department. MDARD also said deer hunting in the northeastern Lower Peninsula remains an important tool for fighting the disease.
The Alcona County case follows detections outside the zone. After bovine TB was found in additional Iosco County cattle herds in September, MDARD proposed an order on Oct. 14 that would require all cattle and bison herds in added township sections of Arenac, Iosco and Ogemaw counties to be tested by July 31, 2027. Testing would cover animals 12 months or older and animals of any age not born on the farm.
A public hearing on that proposal is set for Wednesday from 6 to 8 p.m. at the Plainfield Township Hall, and written comments are due by 5 p.m. Nov. 13. If the MDARD director approves it, the order would take effect Dec. 1. The department has not said when results of the Alcona County investigation or genome sequencing will be available.
