Descriptive Report of Post-Mortem Diagnosis of Bovine Granulomatous Tubercular Pneumonia through Conventional Histological and Immunohistochemical Techniques

Abstract

The study was aimed to diagnose the tubercular lesion of lung in bovine in spontaneous cases through histological and immunohistochemical techniques. In a year-long study of bovine pneumonia cases, 9 cases were suspected for granulomatous tubercular lesion. The tissues from the lesions were subjected for histological and immunohistological examination along with acid fast staining to see the presence of bacteria. The tubercle appeared as small to medium size was more pronounced in right cranial lobes in most of the cases. Histologically small to large granulomas with clusters of cells surrounding centrally caseous necrotic area were observed. The caseous necrotic areas had nuclear debris and were surrounded by granulomatous inflammatory reaction in which dense cluster of lymphocytes, epithelioid cell, macrophages and moderate amount of scattered Langhans’ giant cell. Staining with Ziehl Neelsen (ZN) stain, 7 cases showed low to high numbers of acid fast bacteria in lung section examined out of 9 cases. Immunohistological (IHC) staining with commercial anti-Mycobacterium tuberculosis polyclonal antibody showed positive reaction in Langhan’s giant cell, epithelioid cells and macrophages and in caseous necrotic tissues. As compared to ZN staining, the entire 9 samples were found positive for M tuberculosis antigen by IHC. Generally the intensity and number of positivity were much higher in IHC staining than ZN staining for acid fast bacilli. Thus, the present study shows that immunohistochemistry can be used over conventional histopathology and ZN staining in postmortem diagnosis of bovine tuberculosis and can be applied even in cases with small number of tubercle bacilli.