Human-to-human transmission of tuberculosis caused by Mycobacterium bovis in immunocompetent patients

Risk factors associated with zoonotic tuberculosis at the animal-human interface in a tuberculosis-endemic sub-Saharan country

We aimed to assess the proportion of tuberculosis in humans and tuberculosis (TB)-associated abattoir condemnations from the animal sector, as well as determine risk factors of zoonotic tuberculosis at the animal-human interface in Zambia. The study involved 255 presumptive TB patients and 156 cattle carcasses and was conducted from April 2020 to December 2021. Univariable and multivariable logistic regressions were performed for risk factor analysis for zoonotic TB. The overall proportion of bovine tuberculosis in traditional cattle and the proportion of tuberculosis among presumptive TB patients were 39.7% and 10.2%, respectively. Consumption of raw milk (adjusted odds ratio (AOR)=2.72, 95% confidence interval (CI): 1.73-4.28) and history of previous contact with a TB patient (AOR=1.86, 95% CI: 1.17-2.95) were risk factors for zoonotic TB at the animal-human interface of Zambia. Therefore, community campaigns and sensitization on zoonotic TB transmission are recommended.

Zoonotic tuberculosis in a high bovine tuberculosis burden area of Ethiopia

Background

Tuberculosis (TB) is a major cause of ill health and one of the leading causes of death worldwide, caused by species of the Mycobacterium tuberculosis complex (MTBC), with Mycobacterium tuberculosis being the dominant pathogen in humans and Mycobacterium bovis in cattle. Zoonotic transmission of TB (zTB) to humans is frequent particularly where TB prevalence is high in cattle. In this study, we explored the prevalence of zTB in central Ethiopia, an area highly affected by bovine TB (bTB) in cattle.

Method

A convenient sample of 385 patients with pulmonary tuberculosis (PTB, N = 287) and tuberculous lymphadenitis (TBLN, N = 98) were included in this cross-sectional study in central Ethiopia. Sputum and fine needle aspirate (FNA) samples were obtained from patients with PTB and TBLN, respectively, and cultures were performed using BACTEC™ MGIT™ 960. All culture positive samples were subjected to quantitative PCR (qPCR) assays, targeting IS1081, RD9 and RD4 genomic regions for detection of MTBC, M. tuberculosis and M. bovis, respectively.

Results

Two hundred and fifty-five out of 385 sampled patients were culture positive and all were isolates identified as MTBC by being positive for the IS1081 assay. Among them, 249 (97.6%) samples had also a positive RD9 result (intact RD9 locus) and were consequently classified as M. tuberculosis. The remaining six (2.4%) isolates were RD4 deficient and thereby classified as M. bovis. Five out of these six M. bovis strains originated from PTB patients whereas one was isolated from a TBLN patient. Occupational risk and the widespread consumption of raw animal products were identified as potential sources of M. bovis infection in humans, and the isolation of M. bovis from PTB patients suggests the possibility of human-to-human transmission, particularly in patients with no known contact history with animals.

Conclusion

The detected proportion of culture positive cases of 2.4% being M. bovis from this region was higher zTB rate than previously reported for the general population of Ethiopia. Patients with M. bovis infection are more likely to get less efficient TB treatment because M. bovis is inherently resistant to pyrazinamide. MTBC species identification should be performed where M. bovis is common in cattle, especially in patients who have a history of recurrence or treatment failure.

Genetic Diversity and Population Structure of Mycobacterium bovis at the Human-Animal-Ecosystem Interface in France: “A One Health Approach”

Mycobacterium bovis infects cattle and wildlife, and also causes a small proportion of tuberculosis cases in humans. In most European countries, M. bovis infections in cattle have been drastically reduced, but not eradicated. Here, to determine the M. bovis circulation within and between the human, cattle, and wildlife compartments, we characterized by spoligotyping and mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing the genetic diversity of M. bovis isolates collected from humans, cattle, and wildlife in France from 2000 to 2010. We also assessed their genetic structure within and among the different host groups, and across time and space. The M. bovis genetic structure and its spatiotemporal variations showed different dynamics in the human and animal compartments. Most genotypes detected in human isolates were absent in cattle and wildlife isolates, possibly because in patients, M. bovis infection was contracted abroad or was the reactivation of an old lesion. Therefore, they did not match the genetic pool present in France during the study period. However, some human-cattle exchanges occurred because some genotypes were common to both compartments. This study provides new elements for understanding M. bovis epidemiology in France, and calls for increased efforts to control this pathogen worldwide.

Mycobacterium bovis induced human tuberculosis in India: Current status, challenges & opportunities

Tuberculosis (TB) caused by Mycobacterium tuberculosis is a leading cause of human deaths due to any infectious disease worldwide. However, infection of Mycobacterium bovis, primarily an animal pathogen, also leads to the development of 'human tuberculosis'. Infected animals have been considered the major source of M. bovis infection and humans get exposed to M. bovis through close contact with infected animals or consumption of contaminated milk, unpasteurized dairy products and improperly cooked contaminated meat. The information on the global distribution of bovine TB (bTB) is limited, but the disease has been reported from all the livestock-producing middle- and low-income countries of the world. In recent years, there is a renewed interest for the control of bTB to minimize human infection worldwide. In India, while the sporadic presence of M. bovis has been reported in domestic animals, animal-derived food products and human beings from different geographical regions of the country, the information on the national prevalence of bTB and transmission dynamics of zoonotic TB is, however, not available. The present article reviewed published information on the status of M. bovis-induced zoonotic TB to highlight the key challenges and opportunities for intervention to minimize the risk of M. bovis infection in humans and secure optimum animal productivity in India.

Retrospective analysis of the control and prevention of tuberculosis among cattle in Ukraine in the period 1994–2020

Bovine tuberculosis (bTB) – is a chronic infectious disease, the causative agent of which affects many species of mammals. It is a zoonosis caused by various types of mycobacteria in the complex Mycobacterium tuberculosis family Mycobacteriaceae. The most important etiological agent of bTB in cattle is M. bovis, which has been isolated from tuberculosis infected cattle for centuries. Livestock and species of the Bovidae family are the most susceptible to this pathogen and are the main reservoir species for animals and humans. In Ukraine, the main methods of diagnosing tuberculosis in animal husbandry are lifetime (clinical examination, allergic intradermal test with tuberculin), and postmortem techniques (pathological changes, bacteriological investigation). The authors performed a retrospective analysis of the epizootic situation of tuberculosis among cattle in Ukraine for the period 1994–2020 and conducted a critical assessment of the work done to prevent and control this disease. In total, over the last 27 years, 219 088 head of cattle with tuberculosis and 933 affected locations have been identified in Ukraine. The results of this work showed that in our country the epizootic situation of bovine tuberculosis on farms of various forms of ownership is fully controlled. The most active fight against tuberculosis was carried out during 1995–2015. In 1994–1997, the largest number of affected locations was registered, from 90 to 144, respectively, and the largest number of animals with tuberculosis – 21 395–33 474. In 1994–1995, the largest number of sick animals per one affected point was registered (371.9 and 471.7 head, respectively). Currently, official statistics show that many farms, especially in Vinnytska, Cherkaska and Kyivska regions, continue to show positive allergic reactions to tuberculin (46 898 reactions for the last 12 years). Applying diagnostic methods of research in complex (bacteriological, bioassay, molecular), excludes affection of cattle by pathogenic mycobacteria. This study showed that for the last 5 years no farms with confirmed pathological diagnosis by bacteriological methods have been registered and no culture of the pathogen from animals has been detected. Besides the scurpulous work of the veterinary service, in our opinion, the catastrophic decline in the number of cattle in Ukraine also had a significant impact on improving the epizootic situation regarding tuberculosis.

The puzzle of the evolutionary natural history of tuberculosis

Several pieces of the puzzle of the natural history of tuberculosis are assembled in this review to illustrate the potential reservoirs and sources of the Mycobacterium tuberculosis complex (MTBC) mycobacteria, their transmission to animals and humans, and their fate in populations, in a co-evolutionary perspective. Millennia-old companions of mammalian and human populations, MTBC are detected in the soil, in which they infect and survive within vegetative amoebae and cysts, except for Mycobacterium canettii. Never detected in the sphere of plants, they are transmissible by transcutaneous, digestive and respiratory routes and cause an infection of the lymphatic system with secondary dissemination in most tissues, in which they determine a specific and non-pathognomonic granulomatous inflammatory reaction; in which MTBC survives in dormant form irrespective of MTBC species and mammalian species; indicating that the current epidemiology in mammalian populations is essentially governed by the probabilities of contact between mammalian species and MTBC species. Individual variabilities in clinical expression of tuberculosis are related to MTBC species, strain and inoculum; host genetic factors; acquired modulations of the inflammatory response; and probably human microbiota. This review of the literature suggests an evolutionary natural history of telluric environmental mycobacteria, satellites of unicellular eukaryotes, transmissible to mammals via the digestive and then respiratory tracts, in which they determine a fatal contagious infection that is primarily lymphatic and a quiescence-mimicking encysted form. This review opens perspectives for microbiological and translational medical research.

Occupational exposure and challenges in tackling M. bovis at human-animal interface: a narrative review

Zoonotic tuberculosis caused by Mycobacterium bovis (M. bovis), a member of Mycobacterium tuberculosis complex (MTBC) has increasingly gathered attention as a public health risk, particularly in developing countries with higher disease prevalence. M. bovis is capable of infecting multiple hosts encompassing a number of domestic animals, in particular cattle as well as a broad range of wildlife reservoirs. Humans are the incidental hosts of M. bovis whereby its transmission to humans is primarily through the consumption of cattle products such as unpasteurized milk or raw meat products that have been contaminated with M. bovis or the transmission could be due to close contact with infected cattle. Also, the transmission could occur through aerosol inhalation of infective droplets or infected body fluids or tissues in the presence of wound from infected animals. The zoonotic risk of M. bovis in humans exemplified by miscellaneous studies across different countries suggested the risk of occupational exposure towards M. bovis infection, especially those animal handlers that have close and unreserved contact with cattle and wildlife populations These animal handlers comprising of livestock farmers, abattoir workers, veterinarians and their assistants, hunters, wildlife workers as well as other animal handlers are at different risk of contracting M. bovis infection, depending on the nature of their jobs and how close is their interaction with infected animals. It is crucial to identify the underlying transmission risk factors and probable transmission pathways involved in the zoonotic transmission of M. bovis from animals to humans for better designation and development of specific preventive measures and guidelines that could reduce the risk of transmission and to protect these different occupational-related/populations at risk. Effective control and disease management of zoonotic tuberculosis caused by M. bovis in humans are also hindered by various challenges and factors involved at animal–human interface. A closer look into factors affecting proper disease control and management of M. bovis are therefore warranted. Hence, in this narrative review, we have gathered a number of different studies to highlight the risk of occupational exposure to M. bovis infection and addressed the limitations and challenges underlying this context. This review also shed lights on various components and approaches in tackling M. bovis infection at animal–human interface.

Zoonotic Tuberculosis in Humans: Control, Surveillance, and the One Health Approach

Zoonotic tuberculosis is a reemerging infectious disease in high-income countries and a neglected one in low- and middle-income countries. Despite major advances in its control as a result of milk pasteurization, its global burden is unknown, especially due the lack of surveillance data. Additionally, very little is known about control strategies. The purpose of this review was to contextualize the current knowledge about the epidemiology of zoonotic tuberculosis and to describe the available evidence regarding surveillance and control strategies in high-, middle-, and low-income countries. We conducted this review enriched by a One Health perspective, encompassing its inherent multifaceted characteristics. We found that the burden of zoonotic tuberculosis is likely to be underreported worldwide, with higher incidence in low-income countries, where the surveillance systems are even more fragile. Together with the lack of specific political commitment, surveillance data is affected by lack of a case definition and limitations of diagnostic methods. Control measures were dependent on risk factors and varied greatly between countries. This review supports the claim that a One Health approach is the most valuable concept to build capable surveillance systems, resulting in effective control measures. The disease characteristics and suggestions to implement surveillance and control programs are discussed.

Bovine Tuberculosis: A Re-emerging Zoonotic Infection

Bovine tuberculosis is caused by Mycobacterium bovis (M. bovis), which infects both humans and cattle. In 2018, a dairy farm in Wisconsin was affected by M. bovis, including a farmworker with exposure to the affected herd. Largely eradicated by effective public health strategies in the United States, most cases are now associated with risk factors including occupational hazards, food consumption, and iatrogenic infections. M. bovis continues to cause disease worldwide affecting certain at-risk populations in the United States. Infections more often result in extrapulmonary sequelae and resistance to pyrazinamide is universal. Thus, successful treatment depends on early and correct identification of the mycobacterium species. A One Health approach to control this re-emerging disease is crucial.

Prevalence of bovine tuberculosis in cattle of lower and middle ranges of north-western Himalayas

This study was conducted to ascertain the prevalence of bovine tuberculosis in cattle of different breeds reared under different faming systems and agro-climatic zones of Himachal Pradesh. Tuberculin reactors (17) were detected only in organized dairy farms. Prevalence (15/595, 2.5%) of the disease was highest in animals aged between 5-10 years with 88.2% (15/17) of total reactors being detected in this age group. Tuberculin reactors were found among animal from Red Sindhi crosses (11.8%, 13/110) and pure Jersey/HF animals (2.8%, 4/143). RT-PCR detected M. bovis in milk (20%, 2/10) and lymph node biopsy samples (17.6%, 3/17). M. bovis is zoonotic and shedding of bacteria in milk is a serious public health hazard. Raw milk and products prepared from unpasteurized or raw milk are major vehicles of M. bovis transmission and causation of extra pulmonary tuberculosis in humans.

Epidemiology of Mycobacterium bovis Disease in Humans in England, Wales, and Northern Ireland, 2002-2014

Despite slightly increased cases in these areas, human infection with this cattle pathogen remains rare.

Despite control efforts, Mycobacterium bovis incidence among cattle remains high in parts of England, Wales, and Northern Ireland, attracting political and public health interest in potential spread from animals to humans. To determine incidence among humans and to identify associated factors, we conducted a retrospective cohort analysis of human M. bovis cases in England, Wales, and Northern Ireland during 2002–2014. We identified 357 cases and observed increased annual case numbers (from 17 to 35) and rates. Most patients were >65 years of age and born in the United Kingdom. The median age of UK-born patients decreased over time. For 74% of patients, exposure to risk factors accounting for M. bovis acquisition, most frequently consumption of unpasteurized milk, was known. Despite the small increase in case numbers and reduction in patient age, M. bovis infection of humans in England, Wales, and Northern Ireland remains rare.

Occupational exposure to human Mycobacterium bovis infection: A systematic review

BACKGROUND

Mycobacterium bovis (M. bovis) is the main causative agent of bovine zoonotic tuberculosis. The aim of this systematic review is to highlight the occupational exposure to bovine tuberculosis due to M. bovis.

METHODOLOGY/PRINCIPAL FINDINGS

A computer based literature search was carried out to identify papers published between January 2006 and March 2017. "PubMed, Cochrane Library and Science Direct" databases were searched systematically. Articles presenting the following properties were included: (i) focusing on M. bovis; (ii) concerning occupational exposure to bovine tuberculosis. A quality assessment was performed after selection of studies. Our search strategy identified a total of 3,264 papers of which 29 studies met the inclusion criteria. Of the 29 articles, 17 were cross-sectional studies (6 were of high quality and scored in the range of 6-7, 11 were of moderate quality and scored in the range 3-5), 10 were case reports, and 2 were reviews. Different occupational fields exposing to the disease were described: livestock sector, particularly in contact with dairy cattle (farmers, veterinaries and assistants, abattoir workers) and working in contact with wildlife (hunters, taxidermists).

CONCLUSIONS

A specific guideline for occupational practitioners taking care of employees exposed to bovine tuberculosis is warranted and should be tailored to level of exposure. This review was intended to be the first step of such a project. Articles were identified from various continents and countries with different socio-economic situations, broadening our understanding of the worldwide situation. Published data on occupational exposure in developed countries are scarce. We had to extrapolate findings from countries with higher prevalence of the disease.

Incidence and Drug Resistance of Zoonotic Mycobacterium bovis Infection in Peshawar, Pakistan

Prevalence of zoonotic Mycobacterium bovis (bTB) disease in human population is underreported from the North of Pakistan. Here, we report on the proportion of human bTB disease among the overall TB patients, drug resistance pattern of bTB isolates, and knowledge, attitude, and practices (KAP)-based analysis of bTB disease. For this purpose, sputum samples from a total of 300 clinically diagnosed TB patients and 100 randomly selected school children suspected of pulmonary TB were processed by culture as well as polymerase chain reaction (PCR) for isolation, identification, and confirmation of Mycobacterium tuberculosis (mTB) and bTB species. Isolates of bTB were processed for drug susceptibility tests. Data on KAP regarding TB were obtained on a pretested questionnaire. Sputum-based PCR results indicated that 288/300 (96%) were confirmed as mTB, while 12/300 (4%) were found as bTB diseases. Interestingly, none of the school child was declared positive for either mTB or bTB. Notably, 274/300 (91.3%) positively cultured samples were identified as mTB, 13/300 (4.3%) as bTB, while 5/300 (1.7%) as mixed containing both. Importantly, except one, all of the bTB isolates were found resistant to pyrazinamide. Surprisingly, most of the bTB isolates (~70%) were found resistant to a broad range of first- and second-line anti-TB drugs. SplitsTree and recombination analysis indicated no evidence of intergenic recombination. Finally, residence, occupation, presence of animals at home, and sleeping alongside animals were found significantly associated with occurrence of bTB disease. To the best of our knowledge, we report for the first time on the high (4%) burden of bTB disease in human TB patients in Peshawar, Pakistan.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine tuberculosis

Bovine tuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of bovine tuberculosis to be listed, Article 9 for the categorisation of bovine tuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to bovine tuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, bovine tuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 2, 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (b), (c), (d) and (e) of Article 9(1). The main animal species to be listed for bovine tuberculosis according to Article 8(3) criteria are several mammal species, as indicated in the present opinion.

Human Tuberculosis Caused by Mycobacterium bovis in the United States, 2006-2013

BACKGROUND

Using genotyping techniques that have differentiated Mycobacterium bovis from Mycobacterium tuberculosis since 2005, we review the epidemiology of human tuberculosis caused by M. bovis in the United States and validate previous findings nationally.

METHODS

All tuberculosis cases with a genotyped M. tuberculosis complex isolate reported during 2006-2013 in the United States were eligible for analysis. We used binomial regression to identify characteristics independently associated with M. bovis disease using adjusted prevalence ratios (aPRs) and corresponding 95% confidence intervals (CIs).

RESULTS

During 2006-2013, the annual percentages of tuberculosis cases attributable to M. bovis remained consistent nationally (range, 1.3%-1.6%) among all tuberculosis cases (N = 59 273). Compared with adults 25-44 years of age, infants aged 0-4 years (aPR, 1.9 [95% CI, 1.4-2.8]) and children aged 5-14 years (aPR, 4.0 [95% CI, 3.1-5.3]) had higher prevalences of M. bovis disease. Patients who were foreign-born (aPR, 1.4 [95% CI, 1.2-1.7]), Hispanic (aPR, 3.9 [95% CI, 3.0-5.0]), female (aPR, 1.4 [95% CI, 1.3-1.6]), and resided in US-Mexico border counties (aPR, 2.0 [95% CI, 1.7-2.4]) also had higher M. bovis prevalences. Exclusively extrapulmonary disease (aPR, 3.7 [95% CI, 3.3-4.2]) or disease that was both pulmonary and extrapulmonary (aPR, 2.4 [95% CI, 2.1-2.9]) were associated with a higher prevalence of M. bovis disease.

CONCLUSIONS

Children, foreign-born persons, Hispanics, and females are disproportionately affected by M. bovis, which was independently associated with extrapulmonary disease. Targeted prevention efforts aimed at Hispanic mothers and caregivers are warranted.

Mycobacterium bovis hip bursitis in a lung transplant recipient

We present a report of extrapulmonary Mycobacterium bovis infection in a lung transplant recipient. M. bovis is acquired predominantly by zoonotic transmission, particularly from consumption of unpasteurized foods. We discuss epidemiologic exposure, especially as relates to the Mexico-US border, clinical characteristics, resistance profile, and treatment.

Epidemiology of human Mycobacterium bovis disease, California, USA, 2003-2011

Disease was associated with the Hispanic binational population and immunosuppressive conditions, including diabetes.

We conducted a retrospective review of California tuberculosis (TB) registry and genotyping data to evaluate trends, analyze epidemiologic differences between adult and child case-patients with Mycobacterium bovis disease, and identify risk factors for M. bovis disease. The percentage of TB cases attributable to M. bovis increased from 3.4% (80/2,384) in 2003 to 5.4% (98/1,808) in 2011 (p = 0.002). All (6/6) child case-patients with M. bovis disease during 2010–2011 had >1 parent/guardian who was born in Mexico, compared with 38% (22/58) of child case-patients with M. tuberculosis disease (p = 0.005). Multivariate analysis of TB case-patients showed Hispanic ethnicity, extrapulmonary disease, diabetes, and immunosuppressive conditions, excluding HIV co-infection, were independently associated with M. bovis disease. Prevention efforts should focus on Hispanic binational families and adults with immunosuppressive conditions. Collection of additional risk factors in the national TB surveillance system and expansion of whole-genome sequencing should be considered.

Transmission and Progression to Disease of Mycobacterium tuberculosis Phylogenetic Lineages in The Netherlands

The aim of this study was to determine if mycobacterial lineages affect infection risk, clustering, and disease progression among Mycobacterium tuberculosis cases in The Netherlands. Multivariate negative binomial regression models adjusted for patient-related factors and stratified by patient ethnicity were used to determine the association between phylogenetic lineages and infectivity (mean number of positive contacts around each patient) and clustering (as defined by number of secondary cases within 2 years after diagnosis of an index case sharing the same fingerprint) indices. An estimate of progression to disease by each risk factor was calculated as a bootstrapped risk ratio of the clustering index by the infectivity index. Compared to the Euro-American reference, Mycobacterium africanum showed significantly lower infectivity and clustering indices in the foreign-born population, while Mycobacterium bovis showed significantly lower infectivity and clustering indices in the native population. Significantly lower infectivity was also observed for the East African Indian lineage in the foreign-born population. Smear positivity was a significant risk factor for increased infectivity and increased clustering. Estimates of progression to disease were significantly associated with age, sputum-smear status, and behavioral risk factors, such as alcohol and intravenous drug abuse, but not with phylogenetic lineages. In conclusion, we found evidence of a bacteriological factor influencing indicators of a strain's transmissibility, namely, a decreased ability to infect and a lower clustering index in ancient phylogenetic lineages compared to their modern counterparts. Confirmation of these findings via follow-up studies using tuberculin skin test conversion data should have important implications on M. tuberculosis control efforts.

Investigation of the high rates of extrapulmonary tuberculosis in Ethiopia reveals no single driving factor and minimal evidence for zoonotic transmission of Mycobacterium bovis infection

Background

Ethiopia, a high tuberculosis (TB) burden country, reports one of the highest incidence rates of extra-pulmonary TB dominated by cervical lymphadenitis (TBLN). Infection with Mycobacterium bovis has previously been excluded as the main reason for the high rate of extrapulmonary TB in Ethiopia.

Methods

Here we examined demographic and clinical characteristics of 953 pulmonary (PTB) and 1198 TBLN patients visiting 11 health facilities in distinct geographic areas of Ethiopia. Clinical characteristics were also correlated with genotypes of the causative agent, Mycobacterium tuberculosis.

Results

No major patient or bacterial strain factor could be identified as being responsible for the high rate of TBLN, and there was no association with HIV infection. However, analysis of the demographic data of involved patients showed that having regular and direct contact with live animals was more associated with TBLN than with PTB, although no M. bovis was isolated from patients with TBLN. Among PTB patients, those infected with Lineage 4 reported “contact with other TB patient” more often than patients infected with Lineage 3 did (OR = 1.6, CI 95% 1.0-2.7; p = 0.064). High fever, in contrast to low and moderate fever, was significantly associated with Lineage 4 (OR = 2.3; p = 0.024). On the other hand, TBLN cases infected with Lineage 4 tended to get milder symptoms overall for the constitutional symptoms than those infected with Lineage 3.

Conclusions

The study suggests a complex role for multiple interacting factors in the epidemiology of extrapulmonary TB in Ethiopia, including factors that can only be derived from population-based studies, which may prove to be significant for TB control in Ethiopia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-0846-7) contains supplementary material, which is available to authorized users.

Standing of nucleic acid testing strategies in veterinary diagnosis laboratories to uncover Mycobacterium tuberculosis complex members

Nucleic acid testing (NAT) designate any molecular approach used for the detection, identification, and characterization of pathogenic microorganisms, enabling the rapid, specific, and sensitive diagnostic of infectious diseases, such as tuberculosis. These assays have been widely used since the 90s of the last century in human clinical laboratories and, subsequently, also in veterinary diagnostics. Most NAT strategies are based in the polymerase chain reaction (PCR) and its several enhancements and variations. From the conventional PCR, real-time PCR and its combinations, isothermal DNA amplification, to the nanotechnologies, here we review how the NAT assays have been applied to decipher if and which member of the Mycobacterium tuberculosis complex is present in a clinical sample. Recent advances in DNA sequencing also brought new challenges and have made possible to generate rapidly and at a low cost, large amounts of sequence data. This revolution with the high-throughput sequencing (HTS) technologies makes whole genome sequencing (WGS) and metagenomics the trendiest NAT strategies, today. The ranking of NAT techniques in the field of clinical diagnostics is rising, and we provide a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis with our view of the use of molecular diagnostics for detecting tuberculosis in veterinary laboratories, notwithstanding the gold standard being still the classical culture of the agent. The complementary use of both classical and molecular diagnostics approaches is recommended to speed the diagnostic, enabling a fast decision by competent authorities and rapid tackling of the disease.

Rapid identification of veterinary-relevant Mycobacterium tuberculosis complex species using 16S rDNA, IS6110 and Regions of Difference-targeted dual-labelled hydrolysis probes

Members of the Mycobacterium tuberculosis complex (MTC) are causative agents of tuberculosis (TB) in both humans and animals. MTC species are genetically very similar but may differ in their epidemiology, namely geographic distribution and host preferences, virulence traits and antimicrobial susceptibility patterns. However, the conventional laboratory diagnosis does not routinely differentiate between the species of the MTC. In this work we describe a rapid and robust two-step five-target probe-based real-time PCR identification algorithm, based on genomic deletion analysis, to identify the MTC species most commonly associated with TB in livestock and other animals. The first step allows the confirmation of the cultures as MTC members, by targeting their IS6110 element, or as a mycobacterial species, if only a 16S rDNA product is detected in the duplex amplification reaction. If a MTC member is identified, the second amplification step allows the assessment of the presence or absence of the RD1, RD4 and RD9 genomic regions. The correspondent pattern allows us to infer the species of the isolate as M. tuberculosis (if all RDs are present), Mycobacterium caprae (if only RD1 and RD4 are present) and Mycobacterium bovis (if only RD1 is present). The identification algorithm developed presented an almost perfect agreement with the results of the routine bacteriological analysis, with a kappa coefficient of 0.970 (CI(P95%) 0.929-1.000). The assay is able to be adaptable to automation and implementation in the routine diagnostic framework of veterinary diagnostic laboratories, with a particular focus for reference laboratories.

Relevance of bovine tuberculosis research to the understanding of human disease: historical perspectives, approaches, and immunologic mechanisms

Pioneer studies on infectious disease and immunology by Jenner, Pasteur, Koch, Von Behring, Nocard, Roux, and Ehrlich forged a path for the dual-purpose with dual benefit approach, demonstrating a profound relevance of veterinary studies for biomedical applications. Tuberculosis (TB), primarily due to Mycobacterium tuberculosis in humans and Mycobacterium bovis in cattle, is an exemplary model for the demonstration of this concept. Early studies with cattle were instrumental in the development of the use of Koch's tuberculin as an in vivo measure of cell-mediated immunity for diagnostic purposes. Calmette and Guerin demonstrated the efficacy of an attenuated M. bovis strain (BCG) in cattle prior to use of this vaccine in humans. The interferon-γ release assay, now widely used for TB diagnosis in humans, was developed circa 1990 for use in the Australian bovine TB eradication program. More recently, M. bovis infection and vaccine efficacy studies with cattle have demonstrated a correlation of vaccine-elicited T cell central memory (TCM) responses to vaccine efficacy, correlation of specific antibody to mycobacterial burden and lesion severity, and detection of antigen-specific IL-17 responses to vaccination and infection. Additionally, positive prognostic indicators of bovine TB vaccine efficacy (i.e., responses measured after infection) include: reduced antigen-specific IFN-γ, iNOS, IL-4, and MIP1-α responses; reduced antigen-specific expansion of CD4(+) T cells; and a diminished activation profile on T cells within antigen stimulated cultures. Delayed type hypersensitivity and IFN-γ responses correlate with infection but do not necessarily correlate with lesion severity whereas antibody responses generally correlate with lesion severity. Recently, serologic tests have emerged for the detection of tuberculous animals, particularly elephants, captive cervids, and camelids. B cell aggregates are consistently detected within tuberculous lesions of humans, cattle, mice and various other species, suggesting a role for B cells in the immunopathogenesis of TB. Comparative immunology studies including partnerships of researchers with veterinary and medical perspectives will continue to provide mutual benefit to TB research in both man and animals.

Current knowledge and pending challenges in zoonosis caused by Mycobacterium bovis: a review

Mycobacterium bovis is both the causative agent of bovine tuberculosis (TB) and a zoonotic pathogen. In humans, considerably fewer cases of TB are caused by M. bovis than M. tuberculosis; nevertheless, diagnostic limitations mean that currently available data on prevalence grossly underestimate the true dimension of the problem. The routes of transmission from animals to humans are well known and include direct exposure to infected animals or consumption of contaminated animal products. Application of fingerprinting tools facilitates analysis of the molecular epidemiology of M. bovis in animal-to-human and human-to-human transmission. Apart from cattle and M. bovis, other animal species and members within the M. tuberculosis complex can contribute to the zoonosis. Improvements in diagnostic techniques, application of more advanced discriminatory genotyping tools, and collaboration between veterinary and human health care researchers are key to our understanding of this zoonosis.

Enhanced detection of tuberculous mycobacteria in animal tissues using a semi-nested probe-based real-time PCR

Bovine tuberculosis has been tackled for decades by costly eradication programs in most developed countries, involving the laboratory testing of tissue samples from allegedly infected animals for detection of Mycobacterium tuberculosis complex (MTC) members, namely Mycobacterium bovis. Definitive diagnosis is usually achieved by bacteriological culture, which may take up to 6–12 weeks, during which the suspect animal carcass and herd are under sanitary arrest. In this work, a user-friendly DNA extraction protocol adapted for tissues was coupled with an IS6110-targeted semi-nested duplex real-time PCR assay to enhance the direct detection of MTC bacteria in animal specimens, reducing the time to achieve a diagnosis and, thus, potentially limiting the herd restriction period. The duplex use of a novel β-actin gene targeted probe, with complementary targets in most mammals, allowed the assessment of amplification inhibitors in the tissue samples. The assay was evaluated with a group of 128 fresh tissue specimens collected from bovines, wild boars, deer and foxes. Mycobacterium bovis was cultured from 57 of these samples. Overall, the full test performance corresponds to a diagnostic sensitivity and specificity of 98.2% (CI_P95% 89.4–99.9%) and 88.7% (CI_P95% 78.5–94.7%), respectively. An observed kappa coefficient was estimated in 0.859 (CI_P95% 0.771–0.948) for the overall agreement between the semi-nested PCR assay and the bacteriological culture. Considering only bovine samples (n = 69), the diagnostic sensitivity and specificity were estimated in 100% (CI_P95% 84.0–100%) and 97.7% (CI_P95% 86.2–99.9%), respectively. Eight negative culture samples exhibiting TB-like lesions were detected by the semi-nested real-time PCR, thus emphasizing the increased potential of this molecular approach to detect MTC-infected animal tissues. This novel IS6110-targeted assay allows the fast detection of tuberculous mycobacteria in animal specimens with very high sensitivity and specificity, being amenable and cost effective for use in the routine veterinary diagnostic laboratory with further automation possibilities.

(1)H-NMR spectroscopy revealed Mycobacterium tuberculosis caused abnormal serum metabolic profile of cattle

To re-evaluate virulence of Mycobacterium tuberculosis (M. tb) in cattle, we experimentally infected calves with M. tb andMycobacterium bovisvia intratracheal injection at a dose of 2.0×10⁷ CFU and observed the animals for 33 weeks. The intradermal tuberculin test and IFN-γin vitro release assay showed that both M. tb and M. bovis induced similar responses. Immunohistochemical staining of pulmonary lymph nodes indicated that the antigen MPB83 of both M. tb and M. bovis were similarly distributed in the tissue samples. Histological examinations showed all of the infected groups exhibited neutrophil infiltration to similar extents. Although the infected cattle did not develop granulomatous inflammation, the metabolic profiles changed significantly, which were characterized by a change in energy production pathways and increased concentrations of N-acetyl glycoproteins. Glycolysis was induced in the infected cattle by decreased glucose and increased lactate content, and enhanced fatty acid β-oxidation was induced by decreased TG content, and decreased gluconeogenesis indicated by the decreased concentration of glucogenic and ketogenic amino acids promoted utilization of substances other than glucose as energy sources. In addition, an increase in acute phase reactive serum glycoproteins, together with neutrophil infiltration and increased of IL-1β production indicated an early inflammatory response before granuloma formation. In conclusion, this study indicated that both M. tb and M.bovis were virulent to cattle. Therefore, it is likely that cattle with M. tb infections would be critical to tuberculosis transmission from cattle to humans. Nuclear magnetic resonance was demonstrated to be an efficient method to systematically evaluate M. tb and M. bovi sinfection in cattle.

Molecular characterization of Mycobacterium bovis isolates from pastoral livestock at Mikumi-Selous ecosystem in the eastern Tanzania

Domestic ruminants and Wild ungulates can act as reservoir hosts for Mycobacterium bovis, causative agent for bovine tuberculosis (BTB) in animals and man. Bovine tuberculosis (BTB) is endemic in pastoral livestock in Tanzania. There is lack of information on genotypic distribution of M. bovis in animals at wildlife-livestock interface areas and in wildlife conserved areas. The objectives of this study were to characterize and determine the spatial distribution of M. bovis isolates. Tissue samples from cattle and wildlife were cultured and analyzed using deletion typing and spoligotyping techniques. Eight (8.9%) M. bovis strains were isolated from cattle and confirmed by RD4 and RD9 polymerize chain reaction (PCR) assays. Spoligotype SB1467 was the dominant pattern 62.5% (n = 8) in infected animals, two isolates belonged to a newly reported type SB2190, and one isolate belonged to SB0133. The spoligotype patterns of SB1467 and SB0133 were closely related (96.9%) while SB2190 was less related (59.4%) to SB0133, the relatedness amongst spoligotypes were associated with spacer position 15. No M. bovis was isolated from hunted wild animals. The current study has identified a novel spoligotype SB2190. The current data suggest that wild animals in Mikumi-Selous ecosystem are at risk of acquiring M. bovis infection due to occasional interaction by sharing of pasture and water sources between wildlife and livestock. Integrated efforts by all stakeholders are crucial for controlling spread of tuberculosis at livestock/wildlife/human interface areas.

Intrafamilial cluster of pulmonary tuberculosis due to Mycobacterium bovis of the African 1 clonal complex

A new clonal complex of Mycobacterium bovis present at high frequency in cattle from west central African countries has been described as the African 1 (Af1) clonal complex. Here, the first intrafamilial cluster of human tuberculosis cases due to M. bovis Af1 clonal complex strains is reported. We discuss hypotheses regarding modes of transmission.

Dendritic cells in chronic mycobacterial granulomas restrict local anti-bacterial T cell response in a murine model

BACKGROUND

Mycobacterium-induced granulomas are the interface between bacteria and host immune response. During acute infection dendritic cells (DCs) are critical for mycobacterial dissemination and activation of protective T cells. However, their role during chronic infection in the granuloma is poorly understood.

METHODOLOGY/PRINCIPAL FINDINGS

We report that an inflammatory subset of murine DCs are present in granulomas induced by Mycobacteria bovis strain Bacillus Calmette-guerin (BCG), and both their location in granulomas and costimulatory molecule expression changes throughout infection. By flow cytometric analysis, we found that CD11c(+) cells in chronic granulomas had lower expression of MHCII and co-stimulatory molecules CD40, CD80 and CD86, and higher expression of inhibitory molecules PD-L1 and PD-L2 compared to CD11c(+) cells from acute granulomas. As a consequence of their phenotype, CD11c(+) cells from chronic lesions were unable to support the reactivation of newly-recruited, antigen 85B-specific CD4(+)IFNgamma(+) T cells or induce an IFNgamma response from naïve T cells in vivo and ex vivo. The mechanism of this inhibition involves the PD-1:PD-L signaling pathway, as ex vivo blockade of PD-L1 and PD-L2 restored the ability of isolated CD11c(+) cells from chronic lesions to stimulate a protective IFNgamma T cell response.

CONCLUSIONS/SIGNIFICANCE

Our data suggest that DCs in chronic lesions may facilitate latent infection by down-regulating protective T cell responses, ultimately acting as a shield that promotes mycobacterium survival. This DC shield may explain why mycobacteria are adapted for long-term survival in granulomatous lesions.

Tracing the origins of Mycobacterium bovis tuberculosis in humans in the USA to cattle in Mexico using spoligotyping

OBJECTIVES

To compare genotypes of Mycobacterium bovis strains from humans in Southern California with genotypes of M. bovis strains in cattle in Mexico and the USA to explore the possible origins of human infections.

METHODS

We conducted a descriptive analysis of M. bovis genotypes from a binational population of humans and cattle using spacer oligonucleotide typing (spoligotyping).

RESULTS

One hundred six human M. bovis spoligotypes were compared to spoligotypes from 496 Mexican cattle and 219 US cattle. Twelve spoligotype patterns were identified among human cases and 126 spoligotype patterns were detected in cattle. Over 91% (97/106) of the human M. bovis isolates had spoligotypes that were identical to those found in Mexican cattle. Four human cases had spoligotypes that matched both cattle born in Mexico and in the USA. Nine human cases had spoligotypes that did not match cattle born in Mexico or the USA.

CONCLUSIONS

Our data indicate that the population of M. bovis strains causing human TB disease in Southern California is closely related to the M. bovis strain population found in Mexican cattle and supports existing epidemiological evidence that human M. bovis disease in San Diego likely originated from Mexican cattle.