How is bovine TB (bTB) transmitted? What is the current state of the epidemic in Great Britain? Are approaches to eradication working? Josh Loeb spoke with vets and farmers involved in bTB control in England and Wales in the first part in a special series about this most intractable of livestock health problems.

BCG vaccination induces antibacterial effector functions among Vδ1/3 T cells that are associated with protection against tuberculosis.

The natural product fidaxomicin (Fdx) is a narrow-spectrum antibiotic clinically prescribed for the treatment of Clostrodioides difficile infections. However, limited cellular uptake reduces its therapeutic potential, particularly against Gram-negative bacteria and mycobacteria. In this study, we investigated Thiol-Mediated Uptake (TMU) to promote the delivery of Fdx into bacterial cells. We synthesized a library of Fdx derivatives bearing cyclic dichalcogenide moieties and evaluated their antimicrobial properties against C. difficile and Mycobacterium tuberculosis, respectively. Remarkably, the synthetic Fdx derivatives retained strong levels of antibacterial activity, and the disulfide-containing analogs outperformed their all-carbon control counterparts in many instances. We then developed a systematic study to investigate the mechanistic impact of the introduced disulfide functionalities by conducting experiments with TMU inhibitors and quantifying intracellular accumulation in Mycobacterium bovis BCG, a model organism for M. tuberculosis, via LC-MS/MS. While complete disentanglement of the factors influencing activity was not feasible, features such as compound stability and lipophilicity were identified as significant contributors. Overall, the superior performance of disulfide analogs suggests that differences in cellular entry or intracellular processing, potentially related to TMU, are involved. This work highlights that TMU remains a viable approach for modulating the uptake of therapeutic agents into bacterial cells.

Reverse zoonosis in bovine tuberculosis: The neglected threat of Mycobacterium tuberculosis infection in cattle.

Mycobacterium bovis (M. bovis), a member of Mycobacterium tuberculosis complex, can cause tuberculosis in both adults and children. Our study aimed to identify the clinical and laboratory features of children with M. bovis infection. This retrospective descriptive study sampled a cohort of consecutive cases diagnosed as M. bovis infection by culture positivity from October 2013 through May 2023. Epidemiological data were obtained on gender, age, region of residence, clinical signs, exposure, treatment, and outcome. The analysis was performed using descriptive statistics. M. bovis was found to be the causative agent in seven of 25 patients with culture-confirmed tuberculosis, but M. bovis mostly caused extrapulmonary disease, the most frequent clinical form being cervical lymphadenitis. The most common symptoms were fever and neck swelling. No resistance was detected, except to pyrazinamide, in the strains. M. bovis has a significant disease burden in children. Advanced typing is recommended for M. tuberculosis complex culture positivity to determine the appropriate treatment regimen.

BackgroundIndia faces the highest burden of human and bovine tuberculosis (TB) globally. Despite this, the association between human TB and livestock exposure remains poorly understood. This exploratory study aimed to evaluate the association between human TB and livestock contact in Wardha district, Maharashtra, India.MethodsA case-control study was conducted from 01/03/2021 to 31/03/2022. Cases were microbiologically confirmed TB patients in HDSS villages, while controls were asymptomatic individuals from the same villages without TB history. Livestock in these households (HHs) were screened for TB using Interferon-Gamma-Release-Assay (IGRA), Single Cervical-Test (SCT), and Comparative-Cervical-test (CCT). Additionally, community-pooled milk samples were cultured for Mycobacterium tuberculosis complex. Fisher’s exact test was used to calculate crude odds ratios and logistic regression for adjusted odds ratios (AOR) with 95% confidence intervals (CI). A post hoc exploratory analysis to understand the relationship between effect size and sample size requirements was done.ResultsThe study included 52 cases and 205 controls, with a median age of 36.5 years (56% men) and 38.5 years (74% men), respectively. Analysis revealed that ownership of livestock and direct contact with cattle did not significantly alter TB risk in humans. Contact with goats showed a marginal association with human TB (AOR: 3.0; 95% CI: 1.0–9.2; p = 0.05). Of 290 livestock screened for TB, none tested positive by confirmatory tests (CCT/IGRA). While 10.2% of cattle showed reactivity to the SIT, this likely represents cross-reactivity with environmental mycobacteria. All bulk milk samples (n = 201) tested negative for MTBC. Post-hoc power analysis revealed that the study had limited statistical power (41%) to detect the observed association with goat contact.ConclusionThis study found no evidence of bovine TB in livestock or milk samples. While contact with goats showed a marginal association requiring further investigation, livestock ownership and raw milk consumption did not show strong associations with human TB. The absence of confirmed TB in animals suggests zoonotic transmission is not a significant contributor to human TB in this setting. The results highlight the need for larger, regionally diverse studies to better understand livestock-associated TB risk factors in India.

Plasma exosomes reveal insights into bovine tuberculosis pathogenesis and diagnostic opportunities.

Paratuberculosis (PTB) is a disease affecting ruminant animals. The etiological agent, Mycobacterium avium subspecies PTB (Map), is a short, Gram‐positive, acid‐fast bacillus. Due to the nature of PTB, diagnosis often occurs at advanced stages of the disease, following the onset of clinical symptoms and prior dissemination of the agent. The specificity of current humoral diagnostic techniques, such as ELISA, is limited, mainly due to the presence of various species of mycobacteria in the environment and other closely related pathogenic mycobacteria that can interfere with the accurate diagnosis of PTB due to the high rate of gene conservation within the genus. In the present study, we evaluated the effectiveness and specificity of an ELISA based on a Map polyprotein for diagnosing bovine PTB. The efficacy of the polyprotein‐based ELISA was assessed using serum samples from healthy, Map‐infected, and Mycobacterium bovis (MB)‐infected cattle. Specificity was further evaluated using serum samples from healthy and MB‐infected wild animals. Our findings revealed that in most cases, the degree of cross‐reactivity was negligible or low, particularly in cattle, swine, and goats, while it ranged between 10% and 12.5% in sheep and cervids, respectively. These results suggest that the Map polyprotein used in the ELISA represents a valuable tool for the specific diagnosis of PTB in herds.

Dairy consumers' knowledge, attitudes, and practices towards zoonotic bovine tuberculosis in a country without veterinary and public health interventions: A cross-sectional study in Bhutan.

Abattoir surveillance: Identifying risk factors associated with bovine tuberculosis lesion detection in a low prevalence region.

Immune response to co-administration of Bacillus Calmette-Guérin (BCG) and contraceptive vaccines in badgers (Meles meles).

Proteomic insights into the adaptation of Mycobacterium bovis to hypoxic conditions

Background and Aim. Mycobacterium bovis is a zoonotic member of the Mycobacterium tuberculosis complex and the causative agent of bovine tuberculosis, posing significant challenges to veterinary health, wildlife management and public health. Despite high genomic similarity to M. tuberculosis, M. bovis exhibits distinct host–pathogen interaction strategies that influence immune recognition, persistence and disease progression. This review aims to systematize and critically synthesize current knowledge on immunoactive proteins of M. bovis and to elucidate their roles in modulation of innate and adaptive immune responses, with particular emphasis on mechanisms of immune evasion, diagnostic relevance and vaccine potential. Materials and Methods. This narrative review synthesizes peer-reviewed literature retrieved from international scientific databases. Studies addressing molecular genetics, proteomics, tran-scriptomics, host immune signaling pathways, and experimental infection models of M. bovis were critically evaluated. Special attention was given to proteins involved in phagocytosis, autophagy, Toll-like receptor (TLR) signaling and cytokine regulation, as well as to comparative studies with M. tuberculosis. Results. The analysis indicates that M. bovis actively modulates macrophage defense mechanisms through multiple molecular axes, including inhibition of phagosome–lysosome fusion, selective activation of PINK1 Parkin-dependent mitophagy and suppression of xenophagy. Key immunoactive proteins, such as ESAT-6, CFP-10, MPB70/80/83, PE/PPE proteins and lipoproteins, play central roles in shaping both inflammatory and regulatory immune responses. Activation of cytosolic DNA sensors, particularly Interferon-Inducible Protein 204 (IFI204), and downstream IFN-β signaling is more pronounced in M. bovis infection and contributes to species-specific immune responses. Differential expression and secretion of these proteins underpin their value as diagnostic biomarkers and potential vaccine antigens. Conclusion. Immunoactive proteins of M. bovis form a complex molecular network that enables immune modulation, intracellular persistence and host adaptation. Their functional significance extends beyond virulence, positioning them as promising targets for Differentiating Infected from Vaccinated Animals (DIVA)-compatible diagnostics and second-generation vaccines. An integrated understanding of these mechanisms is essential for improving control strategies for bovine tubercu-losis and reducing the risk of zoonotic transmission.

Bovine tuberculosis, caused by Mycobacterium bovis, is a major One Health concern, impacting livestock, wildlife, and humans. The complete genetic and lineage characterization of M. bovis strains is lacking in many parts of the world, including India. This study reports Illumina sequencing and the first draft genome of M. bovis strain 3/86Rv isolated from a cross-bred cow in India in 1986 and kept under in vitro passages. The genome assembly produced a single contig of 4,303,074bp with excellent coverage (99.66%) and completeness, and 97.6% of BUSCO genes were conserved.The genome annotation identified 4,246 coding sequences (CDS). Orthologous cluster analysis revealed high protein conservation among M. bovis strains, with unique genes observed in M. tuberculosis. The subsystems analysis highlighted a significant enrichment of genes related to metabolism, protein processing, and virulence. Phylogenetic analysis placed M. bovis strain 3/86Rv within a closely related cluster of M. bovis isolates and distinct from other MTBC species, such as M. kansasii, which is a more recent outlier. SNP analysis compared with M. bovis AN5 revealed 171 SNPs, with a predominance of missense mutations and a Ts/Tv ratio of 1.11, suggesting adaptive evolution. The study underscores the genetic diversity and complex resistance mechanisms of M. bovis, providing valuable insights into its pathogenicity and evolutionary trajectory. This comprehensive genomic characterization will aid in understanding the biology of M. bovis.

Indicine cattle exhibit superior resistance to Mycobacterium bovis infection compared to taurine breeds, revealing divergent genetic mechanisms underlying bovine tuberculosis (bTB) resilience. Previous research has demonstrated that Cytochrome b-245 (CYBB) gene variants are associated with Mendelian susceptibility to Mycobacterium tuberculosis complex (MTBC) infections. In this study, we analyzed the X-chromosomal sequences from 258 female cattle and identified a divergent missense variant (L237M) in the CYBB gene. This variant occurs at high frequencies in indicine populations. Functional studies using murine macrophages revealed that CYBB L237M mitigates M. tuberculosis-induced ferroptosis by elevating glutathione synthesis and glutathione peroxidase 4 expression. Mechanistically, the L237M substitution enhances the stability of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and p22phox complex (NOX2-p22), which is critical for the generation of phagosomal reactive oxygen species and bacterial clearance. Our findings demonstrate that CYBB L237M promotes intracellular MTBC elimination through ferroptosis suppression, partially explaining the superior bTB resistance of indicine cattle. This study highlights X-chromosomal genetic variation as an evolutionary driver of innate immunity against mycobacterial infections, with implications for breeding strategies and host-directed tuberculosis therapies. The CYBB variant exemplifies how cattle subspecies divergence can illuminate conserved antimicrobial defense mechanisms in mammals.

Bovine tuberculosis (bTB) is a chronic disease of cattle and the leading cause of zoonotic tuberculosis. In Bhutan, there is no dedicated program for bTB despite the country being situated in the bTB enzootic region, where a large section of population relies on cattle and raw milk and, dairy products are widely consumed.To contribute to the design of future education, surveillance, mitigation, and control programs, we investigated the knowledge, attitudes, and practices relevant to bTB among dairy farmers. We surveyed 264 farmers in Thimphu, Paro, and Haa Dzongkhags. These farmers contribute to supplying the eight milk outlets in the capital, Thimphu. We found that only 11 farmers (4.2%; confidence interval 95%: 2.1% - 7.3%) were aware that bTB existed, and only five of them (1.9%; CI 95%: 0.6% – 4.3%) were aware that bTB is a zoonosis. Risk perception and practice followed a gradient of variation from Thimphu to Haa, but overall, we found a correlation between bTB risk perception for animals and humans. Farmers and traders, along with the consumption of meat and sick animals, were perceived as occupations and activities involving the highest risk of zoonotic infection. Contact with animals entering the herd and with neighbouring cattle were perceived as the highest risk for animal infection. Most farmers in Haa consume raw milk and dairy products they produced by themselves, whereas farmers in Paro and Thimphu prefer powdered milk. Using generalised low-rank models and k-means clustering, we found that dzongkhag of residence and attitudes toward zoonotic infection prevention explained most variability in the data. The severe knowledge deficits about bTB are particularly concerning given the zoonosis is present in Bhutan, is prevalent in neighbouring countries, and negatively affects cattle health and well-being, diminishing fertility, milk, and overall productivity, ultimately impacting farmers’ livelihoods and undermining Bhutan’s nutritional and economic reliance on this sector. Urgent short and mid-term activities should be prioritised to identify bTB high-risk areas, educate farmers, and mitigate bTB impacts.

Bovine tuberculosis is a chronic granulomatous disease caused by Mycobacterium tuberculosis var bovis. Despite control programs, bovine tuberculosis presents a significant challenge worldwide and it remains a concern in Brazil. Neurotuberculosis is a relatively rare form of the disease in which Mycobacterium reaches the central nervous system, leading to the formation of multiple small granulomas on the meningeal surface. This study reports a case of neurotuberculosis in an 8-month-old Holstein-Friesian calf from the state of Rio Grande do Sul, southern Brazil. The clinical course was chronic, of nearly five months, and clinical signs were mainly neurological, including ataxia, motor incoordination, stiff neck, muscular tremors, and seizures. These clinical signs resulted from granulomatous lesions affecting the central nervous system. Similar granulomas were also present in the lungs, mediastinal and mesenteric lymph nodes, and adrenal glands. Histologically the granulomas were characterized by caseous necrosis associated to inflammatory infiltration of epithelioid macrophages, Langhans multinucleated giant cells, lymphocytes, and plasma cells, proliferation of fibrous tissue, as well as occasional mineralization. Ziehl-Neelsen staining method yielded acid-alcohol resistant bacilli amidst necrotic debris and in the cytoplasm of Langhans cells. Clinic-pathological findings, postmortem and histological examinations, along with Ziehl-Neelsen staining, confirmed the diagnosis of neurotuberculosis in the present case. This report highlights the importance of control measures for tuberculosis, given the debilitating and zoonotic nature of the disease and the lack of effective treatment.

Tuberculosis (TB) and paratuberculosis (pTBC) are chronic, progressive, and debilitating infectious bacterial diseases caused by Mycobacterium bovis and Mycobacterium avium subsp. paratuberculosis, respectively. Their definitive hosts are cattle, although domestic and wild mammals are also considered accidental hosts. The objective of this study was to determine the seroprevalence for both pathogens using enzyme-linked immunosorbent assays (ELISA). The study was conducted in the commune of San Carlos, Punilla province, Ñuble region, Chile. Fifty blood samples were collected from cattle in three dairy farms. Of the 50 samples, 12 (24%) were seropositive for TB and 13 (26%) for pTBC, while the other 9 samples (18%) were positive for both diseases (co-infection). In the analysis by age group of animals positive for both diseases, 5 (19%) positive samples were found in cows <5 years old and 4 (17%) samples in cows >5 years old or older (p>0.05).

Genomic insights into Mycobacterium orygis in wild ungulates in Chennai, India.

BackgroundThe Bacille Calmette-Guérin (BCG) vaccine, developed in the early 20th century, remains the only widely approved prophylactic against tuberculosis (TB). It was derived from an attenuated strain of Mycobacterium bovis. Its protective efficacy against pulmonary TB in adolescents and adults varies from 0 to 80%; genetic differences among worldwide vaccine strains contribute to this variation. The Brazilian vaccine strain used until 2017, BCG Moreau, is considered a primitive strain and more immunogenic, closer to the original BCG when compared to newer strains, such as BCG Pasteur. The characterization of BCG daughter-strains can contribute not only to a better understanding of the vaccine and its protective effect, but also to elucidating how different BCG culture conditions may contribute to the impact on the host’s immune response. Thus, we aimed to characterize the differences in gene expression through the intracellular proteomic profile of BCG Moreau and Pasteur strains, cultivated in Sauton or 7H9 media, using two-dimensional electrophoresis (2DE) and mass spectrometry.ResultsComparative 2DE analysis of 7H9-cultured BCG strains showed 7 upregulated proteins in BCG Pasteur versus only 2 in BCG Moreau. This profile, however, was different for cultures obtained in the Sauton media, in which 6 proteins were upregulated in BCG Moreau compared to only 3 in BCG Pasteur. The comparison of 2DE profiles from the same strain under these 2 cultivation forms revealed that BCG Moreau regulates 19 proteins when grown in Sauton media, with 17 upregulated, while BCG Pasteur modulated the expression of 10 proteins, 7 upregulated when compared to growth in 7H9. These findings might indicate that the BCG Moreau strain needs to regulate its protein composition more strongly than Pasteur to adapt to adverse conditions of growth and cultivation.ConclusionsThe analysis of the intracellular 2DE profile reveals differences between cultivation methods as well as between the two M. bovis BCG vaccine strains, Moreau and Pasteur. Our results identify important proteins that may contribute to elucidating differences in vaccine efficacy, highlighting the importance of culture conditions when comparing different studies. These findings contribute to the characterization of the Brazilian vaccine strain, BCG Moreau under growth conditions similar to those used in vaccine production.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12866-025-04529-9.