Assam Agricultural University Khanapara, Guwahati-781 022, Assam, India.

Bovine tuberculosis (BT) is a bacterial zoonotic disease which causes serious animal health problem and enormous economic loss to the dairy sector in India. Present investigation was conducted to study the pathological alterations of different organs in bovine tuberculosis. Lungs were observed to be the most affected organs and their lesions included protrusive, hard, whitish to whitish yellow nodules ranging from 2-5mm to 2cm in diameter. Liver, lymph node, spleen, pleura, peritoneum, stomach and genital organs also revealed similar type of lesions. Microscopically, pulmonary lesions were graded in four stages i.e viz. I, II, III and IV on the basis of accumulation of epithelioid macrophages, lymphocytes, presence of multinucleated giant cells, connective tissue rim, central necrosis and mineralization. Liver showed extensive fibrosis and necrosis (caseous and/or coagulative) with infiltration of epithelioid cells, macrophages and formation of giant cell. Lymph nodes revealed the presence of central caseo-necrotic area with varying degree of calcification. Granulomatous changes have also been observed in spleen, pleura, peritoneum, uterus and fore-stomach. Large number of acid-fast rod shaped bacteria was seen within the cytoplasm of macrophages, giant cells and also in the necrotic masses with Ziehl-Neelsen’s stain.