Reversible zoonotic transmission of TB from humans to dairy cattle.

<sec><title>OBJECTIVE</title>To use molecular techniques to assess the prevalence of M. bovis and M. tuberculosis in tuberculin-positive dairy cattle and to identify the risk factors for TB in these animals.</sec><sec><title>METHODS</title>A cross-sectional study was conducted from 2018 to 2020 across Mymensingh, Sirajgonj and Dhaka Districts in Bangladesh. The single intradermal comparative cervical tuberculin test was administered to 1,580 cattle suspected of having bovine TB using both avian and bovine purified protein derivative. Milk and lung tissue samples from positive animals were examined using polymerase chain reaction (PCR) to detect the causative agents of TB. Multivariable logistic regression model identified risk factors, and Sanger's dideoxy sequencing method was used for the phylogenetic analysis of PCR amplicons.</sec><sec><title>RESULTS</title>Simplex PCR identified Mycobacterium tuberculosis complex in 12.6% of samples. Multiplex PCR detected M. bovis in 6.3% and M. tuberculosis in 3.1% of the samples. Phylogenetic analysis of 12 IS6110 gene sequences (8 M. bovis, 4 M. tuberculosis) confirmed alignment with human isolates from Bangladesh.</sec><sec><title>CONCLUSION</title>The study suggests potential reverse zoonotic transmission of M. tuberculosis. Further research is needed to understand the implications and assess TB transmission between humans and cattle in Bangladesh. The findings highlight the need for a comprehensive One Health approach.</sec>.