Bovine tuberculosis (bTB) is a contagious disease affecting cattle worldwide. It is caused by infection with Mycobacterium bovis. It is characterized by the presence of granulomas (nodular lesions) mainly in the lungs and regional lymph nodes of cattle.

Transmission
M. bovis is able to be transmitted indirectly to cattle from inhalation or ingestion of environmental substrates contaminated through infected animal shedding of M. bovis in their feces. Also, earthworms can get infected with M. bovis through ingestion of contaminated cattle feces, and then they are able to shed the bacteria for up to 4 days in the soil. Badgers are natural carriers of M. bovis and are able to shed the bacteria in their feces.

Regulatory requirements in the United States
Many states require testing of cattle to confirm that they are not infected with M. bovis before moving across state lines.