Vetnuus | March 2026 25 Among zoonotic MTBC members, M. bovis is intrinsically resistant to pyrazinamide (PZA), a key anti-tuberculosis drug. Its growth is inhibited on glycerol-containing media but is supported on media supplemented with pyruvate (4). Mycobacterium orygis, originally isolated from African antelopes, is increasingly implicated in human tuberculosis in South Asia. Clinical isolates, often associated with extrapulmonary disease, have been reported in India, Bangladesh, and Nepal (1,3). Genomic features distinguishing M. orygis include deletion of region of difference (RD) 12 and specific singlenucleotide polymorphisms (SNPs) in genes such as PPE55 and Rv2042c (1). Mycobacterium caprae, once considered a subtype of M. bovis, is now recognised as a distinct species, primarily affecting goats but also occasionally infecting cattle and wildlife. Human infections have been reported in Europe and are frequently resistant to PZA (11). Distinction from other MTBC species can be achieved through gyrB polymorphisms and RD-based analysis. Unlike the person-to-person aerosol transmission of M. tuberculosis, zoonotic MTBC species are typically acquired through ingestion of contaminated dairy products or through occupational exposure to infected animals or aerosols, often resulting in extrapulmonary disease (5). The zoonotic potential of animal-adapted MTBC species, such as M. orygis and M. caprae, remains underrecognized due to diagnostic limitations and the lack of routine species-level identification in clinical laboratories (12). Furthermore, wildlife reservoirs, including deer, badgers, elephants, and non-domesticated bovines, contribute to complex transmission dynamics, posing challenges for both human and veterinary health sectors (4,10). Understanding the transmission ecology of zTB is crucial for implementing effective surveillance and control measures within the One Health framework (13). Accurate identification of zoonotic MTBC species in both human and animal hosts is a prerequisite for tracking transmission pathways and preventing further spillover events. CONVENTIONAL LABORATORY DIAGNOSTIC METHODS Zoonotic tuberculosis is clinically indistinguishable from tuberculosis caused by M. tuberculosis, presenting with similar granulomatous pathology across affected organs (5). However, the route of infection—most commonly ingestion or occupational exposure—predisposes zTB to extrapulmonary manifestations, such as gastrointestinal, lymphatic, or skeletal tuberculosis (8).Consequently, clinical suspicion alone rarely prompts species-level identification, and diagnosis relies heavily on laboratory investigations. A range of diagnostic options, including microscopy, culture, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), molecular approaches, and serological methods, have been applied in the diagnosis of zTB (4). These methods differ substantially in diagnostic performance, availability, and level of validation. For rare conditions such as zTB, robust evaluation data are often limited due to the scarcity of well-characterised samples. Moreover, culture-based methods require biosafety level 3 (BSL3) laboratory infrastructure, which is not universally available. In such settings, serological and molecular assays performed on inactivated samples may represent practical alternatives (10). Multiple subsequent tests using various diagnostic platforms in a stepwise approach may improve overall sensitivity and specificity. Rapid diagnostic tests (RDTs), which are inexpensive and easy to use, may support disease control efforts; however, their implementation should not preclude access to state-of-the-art diagnostic technologies in low- and middle-income countries (10). Article >>>26 Species Human pathogen Year of description First isolation source M. tuberculosis Frequent 1883 Mainly humans M. bovis Frequent 1907 Cattle (Bos taurus) Greater kudu (Tragelaphus strepsiceros) Common duiker (Sylvicapra grimmia) M. bovis BCG Rare NA - M. africanum Frequent 1969 Castets and colleagues in 1968 based on isolates from human tuberculosis patients in Senegal. M. caprae Occasional 2003 Goats (Capra aegagrus hircus) M. microti Rare 1957 Field voles (Microtus agrestis) M. pinnipedii Rare 2003 Seals and sea lions (e.g., South American sea lion, Otaria flavescens; hooded seals, Cystophora cristata) M. mungi No 2010 Banded mongooses (Mungos mungo) M. suricattae No 2013 Meerkats (Suricata suricatta) M. orygis Rare 2012 East African oryx (Oryx beisa) M. canetti Rare NA - Table 1. Summary of the known MTBC members, their pathogenicity in humans, first isolation sources, and key differentiating features (adapted from reference 11).
RkJQdWJsaXNoZXIy OTc5MDU=