The classic lesion associated with tuberculosis is the tubercle, a tumor-like mass that can grow to great size. In primates and cattle, the primary lesion is usually in the lungs. In deer and poultry, the most common site is the abdomen. Lesions and involved lymph nodes become filled with white, creamy, caseous material, often with mineralization. TB lesions may become walled off with thick fibrous tissue, slowing down the spread of the disease.
Clinical findings depend on the extent and location of the lesions.
Tuberculosis is most commonly a chronic disease leading to emaciation, weakness and difficulty breathing and coughing when the lungs are affected. Animals may show no signs for long periods of time, particularly when lesions have been walled off. The public health importance of bovine TB as well as the negative economic impact on the cattle farmer led to the implementation of the nationwide TB eradication program in 1917. The program followed a test and slaughter regime and has been very successful in reducing the infection rate to an extremely low level. Currently, New York State is classified as TB Free.