Molecular detection, isolation, and pathology of bovine tuberculosis in an organized farm in Assam, India

Bovine tuberculosis (bTB) is a well-known zoonotic disease that affects cattle all over the world and results in significant economic loss, particularly in impoverished nations. The present communication describes the pathology, isolation and molecular detection of Mycobacterium in an organized farm of Assam which has the previous records on animals with confirmed M. bovis infection. During the period 2020-2021, a total of 40 animals (4 males and 36 females) of one year and above were included in the present study for screening of bovine tuberculosis by single intradermal comparative tuberculin test (SICCT). The milk, nasal swabs were collected from only tuberculin positive cattle and the tissue samples from necropsied animal and then processed for bacteriology, histopathology and molecular detection from direct samples. Out of 40, four cows showed positive reactor by SICCT and out of these four, one animal died. At necropsy, there was presence of circumscribed yellowish white lesions of various sizes and numbers. The smear prepared from granulomatous tissue samples showed the presence of acid-fast bacilli by Ziehl-Neelsen stain. Mycobacterium could be isolated from tissue samples. The DNA extracted from the samples could amplify Mycobacteria genus specific hsp65 gene and MTBC specific a 123-bp segment of the insertion sequence IS6110.