Pathological investigation and molecular detection of bacterial zoonotic diseases of slaughtered cattle in Bangladesh

The research was undertaken to investigate the important bacterial zoonotic diseases in slaughtered cattle in Mymensingh district of Bangladesh. The targeted diseases were tuberculosis (TB), leptospirosis, listeriosis, and brucellosis. Samples (mesenteric lymph nodes, lungs, and liver) were collected from 50 slaughtered cattle from different slaughterhouses in Mymensingh district during the periods from October 2019 to November 2021. The diagnosis was made based on gross pathological findings and histopathology by hematoxylin and eosin staining and acid-fast staining. The confirmatory diagnosis was done by polymerase chain reaction using disease-specific primers. Grossly, calcifications and caseation of mesenteric lymph nodes, caseous nodule formation in the liver and lungs, and enlarged mesenteric lymph nodes were the predominant lesions seen. Histopathologically, caseous necrosis and calcification surrounded by fibrous connective tissues in the mesenteric lymph nodes, and granuloma mixed with acid-fast bacteria in the liver were seen as suggestive of infectivity due to TB. Marked lymphoid depletion was seen in listeriosis suspected cases. The PCR amplified Mycobacterium tuberculosis complex (372 bp/16S rRNA), M. bovis (MPB83/600 bp), Leptospira interrogans serovar Hardjoprajitno (HP/323 bp) and Listeria monocytogenes (InlC/517 bp) species-specific amplicons in 09, 09, 05, and 05 cattle, respectively. Brucellosis was not identified in any cases in this study. In conclusion, deadly zoonotic diseases (TB, leptospirosis, and listeriosis) are present in slaughtered cattle having public health importance. Therefore, more extensive monitoring and epidemiological surveys are necessary for the effective prevention and control of zoonotic diseases of cattle.