M. bovis is a highly contagious, chronic debilitating disease of the maintenance hosts. Characteristically, tubercles, or nodular granulomas, may be seen on postmortem examination in the lymph nodes or affected tissue. The resulting caseation and calcification, excluding the skeletal muscles, contribute to the clinical symptoms of the disease. In all maintenance hosts, the disease can be contracted either via aerosol or ingestion, causing a non-pulmonary or pulmonary form of the disease and clinical symptoms of either form can take months or years to develop.