Pathomorphological study of atypical pulmonary tuberculosis in cross-bred cow - A case report

Abstract

Bovine tuberculosis (BTB) is a chronic granulomatous caseous-necrotizing inflammatory process that mainly affects the lungs and their draining lymph nodes. The present communication reports a case of pulmonary tuberculosis in a 7-year-old female crossbred cow from university dairy farm, GADVASU, Ludhiana. The animal died with the history of prolonged illness showing signs of respiratory distress and chronic wasting. The cow was also tested positive previously for tuberculosis by intradermal tuberculin testing. At necropsy, lesions were mostly observed in the pleura, lungs and mediastinal lymph nodes, which were characterized by the circumscribed yellowish white lesions of variable sizes (5 mm to 3 cm) and numbers. Microscopically, these lesions were characterized by tubercular granuloma displaying area of central necrosis with or without mineralization surrounded by macrophages, langhan's giant cells, epithelioid cells, lymphocytes, plasma cells, neutrophils and finally encircled by connective tissue capsule. Atypical granulomas were also noticed particularly in mediastinal lymph node and at times in lungs with extensive infiltration of epithelioid cells and without any caseation, calcification and giant cells. Special stain Ziehl-Neelsen confirmed the acid fast bacilli in the impression smear as well as tissue sections collected from the lesions. On the basis of gross, histopathological observations and special staining, the case was diagnosed as that of atypical pulmonary tuberculosis.