Vetnews | Maart 2026 24 « BACK TO CONTENTS Article Zoonotic Tuberculosis: Emerging Species, Diagnostic Approaches and One Health Implications Hindol Maity1,2,3 , Supriya Meshram1 , Keshao Hiwale2 , Pratibha Narang3 1. Department of Microbiology, Datta Meghe Institute of Higher Education and Research, Sawangi, Wardha, Maharashtra, India 2. Department of Pathology, Datta Meghe Institute of Higher Education and Research, Sawangi, Wardha, Maharashtra, India 3. Department of Microbiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha, Maharashtra, India ABSTRACT Zoonotic tuberculosis (zTB), a form of human tuberculosis caused by animal-adapted members of the Mycobacterium tuberculosis complex (MTBC), poses unique challenges for clinical diagnosis, surveillance, and public health control. Traditionally associated with Mycobacterium bovis and transmitted through the consumption of unpasteurized milk or direct contact with infected animals, zTB is now increasingly attributed to emerging MTBC species, such as Mycobacterium orygis and Mycobacterium caprae, especially in South Asia and Europe. Current diagnostic tools, ranging from microscopy and culture to molecular assays, often lack routine species-level resolution in most clinical settings, contributing to underreporting and mismanagement, particularly in extrapulmonary TB cases. This review aims to explore the diagnostic landscape of zTB, outlining the limitations of conventional methods and highlighting the potential of emerging technologies, including polymerase chain reaction (PCR)based region-of-difference (RD) typing, line probe assays, next-generation sequencing, and clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics. The review also underscores the importance of integrating human, animal, and environmental data within the One Health framework. It advocates for expanded molecular speciation in clinical workflows and improved coordination between veterinary and human health systems. Recognising the full zoonotic spectrum of tuberculosis is essential for achieving accurate surveillance, informed treatment decisions, and meaningful progress toward global TB elimination. INTRODUCTION Zoonotic tuberculosis (zTB) is a form of human tuberculosis caused by animal-adapted members of the Mycobacterium tuberculosis complex (MTBC) (1). Historically, Mycobacterium bovis has been regarded as the principal agent of zTB, with transmission primarily occurring through the ingestion of unpasteurized dairy products or direct contact with infected animals (2). However, recent molecular and genomic studies have revealed that other MTBC members, particularly Mycobacterium orygis and Mycobacterium caprae, also play important roles in zoonotic transmission, especially in geographically and ecologically distinct regions such as South Asia and parts of Europe (3). These findings underscore the need to re-examine current diagnostic and surveillance strategies. Unlike M. tuberculosis, which is primarily transmitted from person to person via aerosols, zoonotic MTBC species are typically transmitted through ingestion, occupational exposure, or environmental contact (4). Their clinical presentations often involve extrapulmonary manifestations, affecting lymph nodes, the gastrointestinal tract, or bones, and may be clinically indistinguishable from disease caused by humanadapted M. tuberculosis (5). According to the World Health Organisation (WHO) estimates, zTB due to M. bovis accounts for approximately 1.4% of the global human TB burden, equivalent to over 140,000 new cases annually, with the highest proportions reported in Africa and parts of SouthEast Asia. These figures likely underestimate the true magnitude due to underreporting and limited species-level identification (6). Conventional tools, such as smear microscopy and culture, do not differentiate among MTBC species (3). Even advanced diagnostics, such as molecular line probe assays (LPAs) and whole-genome sequencing (WGS), are not routinely available in resource-limited settings, where the risk of zTB may be highest (7,8). Moreover, current WHO diagnostic guidelines for tuberculosis do not mandate species-level identification of MTBC in clinical practice, further compounding this diagnostic blind spot (9). Given the shared ecology of humans and animals in many parts of the world, zTB represents not only a clinical challenge but also a public health concern requiring integrated, cross-sectoral approaches (10). The One Health framework, which emphasizes collaboration between human, veterinary, and environmental health sectors, offers an ideal platform for improving surveillance, diagnosis, and control of zTB. This review provides a comprehensive overview of laboratory methods for diagnosing zTB, highlighting both conventional and emerging technologies. Special attention is given to their utility in low-resource settings, the role of species-level identification, and the importance of aligning laboratory practices with One Health objectives. ETIOLOGICAL AGENTS AND TRANSMISSION Zoonotic tuberculosis is primarily caused by M. bovis, a slowgrowing, acid-fast bacillus and a key member of the MTBC, which also includes M. tuberculosis, Mycobacterium africanum, M. orygis, M. caprae, Mycobacterium canettii, Mycobacterium pinnipedii, and Mycobacterium microti, as well as the vaccine strain M. bovis bacillus Calmette-Guérin (BCG) (Table 1). While M. bovis is the classical etiologic agent of bovine tuberculosis, it can infect a wide range of domestic and wild animals, including goats, pigs, deer, badgers, and non-human primates, and is capable of crossing the species barrier and causing disease in humans (8).
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