A systematic evidence map investigating zoonotic tuberculosis across Bangladesh has determined that Mycobacterium orygis is the only animal-adapted member of the Mycobacterium tuberculosis complex molecularly confirmed at the shared cattle, captive wildlife, and human interface. Although zoonotic tuberculosis has been classically attributed to Mycobacterium bovis, emerging surveillance across South Asia increasingly links infections to Mycobacterium orygis. In published investigations from Bangladesh, historical claims attributing infections to Mycobacterium bovis lacked species-level discriminatory support, indicating that existing classifications require cautious reinterpretation by veterinary and public health authorities.

Zoonotic tuberculosis is caused by animal-adapted lineages within the broader Mycobacterium tuberculosis complex, yet species-level identification is rarely performed in low- and middle-income countries. Consequently, the actual clinical and epidemiological burden of the disease remains poorly defined. Bangladesh presents key transmission risks, including endemic bovine tuberculosis, an expanding commercial dairy sector, frequent consumption of unpasteurised milk, and growing captive wildlife collections. Despite these established risk factors, previous regional research on animal-adapted mycobacterial species had not undergone systematic synthesis based on the diagnostic reliability of the testing methodologies employed.

To address this gap, researchers conducted a systematic evidence map aimed at collating all published records of zoonotic tuberculosis in Bangladesh and evaluating the laboratory techniques used to detect animal-adapted species in livestock, wildlife, and humans. Following PRISMA 2020 guidelines, the authors systematically searched PubMed, Google Scholar, and BanglaJOL covering literature from the 1970s through June 2026. The search scope was restricted by institutional access constraints, as Scopus, Web of Science, and CAB Abstracts were inaccessible to the review team during the search period.

Methodological appraisal was conducted independently by two reviewers using the Joanna Briggs Institute checklist to evaluate study quality. The reviewers classified each investigation according to a five-level diagnostic evidence hierarchy designed to assess species discrimination. High-stringency assessments at Level 1 required whole-genome sequencing, phylogenetic analysis, regions of difference typing, spoligotyping, or mycobacterial interspersed repetitive unit variable number tandem repeat typing. In contrast, Level 5 encompassed non-discriminatory evaluations restricted entirely to tuberculin skin testing or serological assays. Because the compiled investigations relied on non-comparable testing frameworks, formal meta-analysis was precluded, leading researchers to structure findings as a descriptive evidence map.

Across the reviewed literature, thirty-five studies met the defined inclusion criteria. These comprised twenty-four publications focusing on infection prevalence in cattle and domestic buffaloes, ten studies describing molecular diagnosis and pathogen characterisation across cattle, captive wildlife, and human cohorts, and one publication focused exclusively on molecular diagnosis and characterisation in humans. Most livestock studies relied on lower-tier, non-discriminatory screening methods such as tuberculin skin tests, enzyme-linked immunosorbent assays, or untyped polymerase chain reaction assays. Across these livestock evaluations, researchers reported non-comparable reactor proportions ranging from 1.2 percent to 33.7 percent.

Species-level discrimination was achieved in only a limited subset of investigations categorized within Levels 1 and 2 of the diagnostic evidence hierarchy. These discriminatory marker-based molecular assays confirmed the presence of Mycobacterium orygis in domestic cattle and across at least seven captive wildlife species, specifically including monkeys. Evidence concerning human infections remained scarce across the literature, limited to three published studies. Among these human investigations, tuberculosis surveillance successfully identified a single human infection confirmed as Mycobacterium orygis through high-resolution whole-genome sequencing.

The review revealed that several historical records asserting the presence of Mycobacterium bovis in Bangladesh were based on non-discriminatory polymerase chain reaction or serological tests incapable of reliably differentiating among closely related Mycobacterium tuberculosis complex members. Because Mycobacterium orygis represents the only confirmed animal-adapted species verified with discriminatory molecular tools, the authors concluded that regional zoonotic tuberculosis surveillance must move beyond an exclusive focus on Mycobacterium bovis. Instead, surveillance should integrate definitive species-level identification into a staged, resource-appropriate One Health strategy that systematically connects domestic livestock management, captive wildlife monitoring, and human public health systems.

Subject of Research: Diagnostic evidence mapping of zoonotic tuberculosis across livestock, captive wildlife, and humans in Bangladesh

Article Title: Zoonotic tuberculosis at the cattle–human–captive wildlife interface in Bangladesh: A systematic evidence map

Article References: Islam, S. S., Rahman, A. K. M. A., Rumi, T. B., Akhter, A. H. M. T., Ibrahim, N., Sarker, M. S., Kabir, S. M. L., & Rahim, Z. (2026). Zoonotic tuberculosis at the cattle–human–captive wildlife interface in Bangladesh: A systematic evidence map. PLOS Neglected Tropical Diseases, 20(11), e0014877. https://doi.org/10.1371/journal.pntd.0014877

Image Credits: AI Generated

DOI: 10.1371/journal.pntd.0014877

Keywords: zoonotic tuberculosis, Mycobacterium orygis, Mycobacterium bovis, Mycobacterium tuberculosis complex, Bangladesh, systematic evidence map, One Health, captive wildlife, dairy cattle, buffaloes, tuberculin skin test, whole-genome sequencing, PRISMA 2020, diagnostic evidence hierarchy, unpasteurised milk, spoligotyping, JBI checklist