Bovine Tuberculosis in Raw Milk: A Herd-Level Prevalence Study by PCR and ELISA Testing in Sylhet Region of Bangladesh.

INTRODUCTION: Bovine tuberculosis (bTB) has been a major cause of morbidity and mortality in farm animals and the recent surge of Mycobacterium tuberculosis complex (MTC) in developing countries poses a serious threat to public and animal health. This study aimed to assess the herd-level prevalence and associated risk factors of bovine TB in cattle in northeast regions of Bangladesh.

METHODS: A total of 485 dairy samples (385 from dairy milk and 100 from vendor's milk) were tested by Polymerase Chain Reaction (PCR) and indirect ELISA (enzyme-linked immunosorbent assay) technique at 16 Upazilas from 4 districts in the Sylhet division of Bangladesh. Genomic DNA extracted from milk samples were targeted at IS6110 and RV1506c genomic fragments for PCR.

RESULTS: Among the 385 milk samples tested, 15 milk samples were positive for Mycobacterium genus by PCR (3.90%, 95% CI: 1.95-5.84). Also, 10 samples were found to be positive for M. bovis and the prevalence was 2.60% (95% CI: 1.00-4.19) and only 2 milk samples were positive for M. tuberculosis by PCR whose prevalence was 0.52% (95% CI: 0.00-1.24) respectively in individual milk samples. In vendor's milk sample, the trend was lowered for each bacterium and indirect ELISA results agreed with a similar pattern of prevalence. Cows having chronic cough was one of the significant risk factors of herd-level prevalence.

CONCLUSION: Findings from this study necessitate a comprehensive program for TB surveillance of associated risk factors or protective factors in human, environment and animal interface.