Emerging Threats of Mycobacterium orygis in Zoonotic TB

Current Landscape of Mycobacterium orygis Infections

The emergence of Mycobacterium orygis has emerged as a significant public health issue, particularly in zoonotic tuberculosis (zTB). Historically, the Mycobacterium tuberculosis complex (MTBC) was primarily associated with Mycobacterium bovis in zoonotic infections, but recent findings have revealed M. orygis as a critical pathogen in both animal and human populations (Rani et al., 2025). The ability of M. orygis to infect a broad range of host species, including humans, domestic animals, and wildlife, raises concerns about its epidemiological impact and the effectiveness of existing control measures.

M. orygis has been documented across 14 countries and has been isolated from a variety of animal hosts, including cattle, wild ungulates, and humans (Hugh et al., 2025). The diversity of hosts, particularly in regions like South Asia, where approximately 33.6% of reported cases have originated, emphasizes the need for improved surveillance and understanding of transmission dynamics (Hugh et al., 2025).

Recent studies have indicated that M. orygis might even be more prevalent than M. bovis in certain areas, particularly in India (Maqsood et al., 2024). This shift in understanding highlights the urgent requirement for robust diagnostic methods to accurately identify the pathogen and implement effective control strategies.

Genetic Insights into Mycobacterium orygis and MTBC

Mycobacterium orygis, previously known as oryx bacillus, has undergone significant genetic characterization, revealing its close relation to other members of the MTBC. Genetic analyses show that M. orygis possesses a genome size of approximately 4.29 Mb with a GC content of 65.59%, sharing about 99.9% nucleotide similarity with other MTBC species (Hugh et al., 2025). This genetic homogeneity complicates the differentiation of M. orygis from other MTBC members using traditional methods and underscores the need for advanced molecular diagnostics.

The current understanding of M. orygis genetics has come primarily from whole-genome sequencing and phylogenetic studies. Recent phylogenetic analyses place M. orygis in a distinct clade within the MTBC, suggesting that it shares a common ancestor with species such as M. bovis and M. caprae (Rani et al., 2025). The identification of specific single-nucleotide polymorphisms (SNPs) has been pivotal in differentiating M. orygis from closely related species. For instance, notable SNPs in genes such as gyrB and Rv2042c serve as markers for accurate identification and understanding its epidemiological patterns (Hugh et al., 2025).

Transmission Pathways of Mycobacterium orygis in Animals

Transmission pathways for M. orygis are complex and multifaceted. Evidence suggests that aerosol transmission is a significant route, especially in environments where humans and animals interact closely (Rani et al., 2025). Consumption of contaminated food and water, as well as direct contact with infected animals, have also been implicated in the spread of the bacteria. The potential for zoonotic transmission emphasizes the need for a One Health approach, integrating human, animal, and environmental health strategies.

In regions with high agricultural and livestock interactions, such as South Asia, the transmission dynamics can be particularly pronounced. For example, studies have shown that close contact with infected cattle and the consumption of unpasteurized dairy products significantly increase the risk of human infection (Hugh et al., 2025). Moreover, the potential for reverse zoonosis, where humans transmit the infection back to animals, complicates the epidemiological landscape. The documented case of a dairy worker transmitting M. orygis to a cow in New Zealand exemplifies these complex transmission dynamics (Maqsood et al., 2024).

Clinical Implications of Mycobacterium orygis in Humans

The clinical implications of M. orygis infections in humans can be severe, particularly as the infection may present similarly to classic tuberculosis caused by M. tuberculosis. The recent increase in reported cases in humans, particularly in regions with high zoonotic TB prevalence, is alarming. Infections have manifested in various forms, including pulmonary tuberculosis (PTB) and extrapulmonary tuberculosis (EPTB) (Maqsood et al., 2024).

Clinical symptoms often include persistent cough, fever, weight loss, and night sweats. Diagnosis typically relies on molecular diagnostic tools coupled with traditional culture methods, although the genetic similarity of M. orygis to other MTBC members complicates accurate identification (Hugh et al., 2025).

Infection management mirrors that of M. tuberculosis, involving a combination of first-line anti-tuberculosis medications such as isoniazid, rifampicin, pyrazinamide, and ethambutol (Rani et al., 2025). However, challenges remain due to potential drug resistance and the need for tailored treatment regimens based on the specific strain and patient factors.

Strategies for Zoonotic Tuberculosis Control and Surveillance

Addressing the challenges posed by M. orygis in zoonotic tuberculosis requires a multifaceted approach. Enhancing laboratory diagnostics and surveillance systems is critical in identifying and controlling outbreaks (Hugh et al., 2025). The integration of veterinary and public health surveillance systems under a One Health framework can facilitate better tracking of transmission routes and epidemiological trends.

1. Strengthening Surveillance Systems: Implementing robust surveillance mechanisms in both human and animal populations is essential. This includes regular screening in livestock and wildlife, as well as human health assessments, particularly in high-risk areas.

2. Enhanced Laboratory Diagnostics: Development and deployment of advanced molecular diagnostic tools, such as whole-genome sequencing and targeted PCR assays, can improve the identification of M. orygis and differentiate it from other MTBC members (Maqsood et al., 2024).

3. Education and Awareness: Raising awareness among healthcare providers, veterinarians, and the public regarding the risks associated with zTB, particularly in areas with high livestock interaction, can facilitate better preventive measures.

4. Interventions in Animal Health: Implementing biosecurity measures on farms, such as vaccination and proper management of livestock, can help reduce the transmission of M. orygis from animals to humans.

5. Research and Collaboration: Continued research into the genetic and epidemiological characteristics of M. orygis, coupled with international collaboration, is essential for developing effective control strategies.

FAQ

What is Mycobacterium orygis?

Mycobacterium orygis is a member of the Mycobacterium tuberculosis complex (MTBC) recently identified as a pathogen that can cause tuberculosis in both animals and humans.

How is Mycobacterium orygis transmitted?

Transmission occurs primarily through aerosols, ingestion of contaminated food or water, and direct contact with infected animals. There is also potential for reverse zoonosis, where humans transmit the infection back to animals.

What are the clinical implications of M. orygis in humans?

In humans, M. orygis can cause symptoms consistent with tuberculosis, including persistent cough, fever, and weight loss. Accurate diagnosis is critical and often involves molecular diagnostics.

How can zoonotic tuberculosis be controlled?

Control strategies include enhancing surveillance systems, improving laboratory diagnostics, educating at-risk populations, and implementing biosecurity measures in animal health.

Why is M. orygis considered a neglected pathogen?

Despite its increasing recognition as a cause of zoonotic tuberculosis, M. orygis remains underreported and under-researched, necessitating more focused attention and resources to understand its epidemiology.

References

1. Rani, I., Kumar, R., Singha, H., Riyesh, T., Vaid, R. K., Bhattacharya, T. K., & Shanmugasundaram, K. (2025). Mycobacterium orygis and its unseen impact: re-evaluating zoonotic tuberculosis in animal and human populations. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2025.1505967

2. Hugh, B. T., Sim, E., Crighton, T., & Sintchenko, V. (2025). Emergence of Mycobacterium orygis: novel insights into zoonotic reservoirs and genomic epidemiology. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2025.1568194

3. Maqsood, R., Duffy, S. C., & Azeem, M. (2024). Molecular detection and characterization of the Mycobacterium tuberculosis complex subspecies responsible for bovine tuberculosis in Punjab, Pakistan