Systematic Veterinary Bacteriology and Mycology

Pathogenicity

PATHOGENECITY

Cattle

• Tuberculosis consists of a characteristic lesion – the tubercle. This is an avascular granuloma composed of a caseous necrosis in a central area encircled by a zone of epitheloid cells, and a peripheral zone of lymphocytes, granulocytes and fibroblasts.
• Calcification may be present in the necrotic centers.
• An outer boundary of fibrous tissue is usually present between the lesions and normal tissue.
• Tubercle lesions are more commonly present in the lymphnode, lungs and pleura.
• Military tuberculosis resembling millet seeds with similar lesions in various organs can be formed by the haematogenous route.

Sheep and Goats

• Similar lesions as that of cattle are seen.

Horses

• Common sites are liver, spleen and lungs. In pigs, the skeleton, especially vertebrate and long bones, are common sites.

Birds

• The grayish white granulomatous lesions are found in the liver and they are also present in the intestines, spleen and bone marrow.