Mycobacterium bovis infection at the interface between domestic and wild animals in Zambia

Tuberculosis in wild animals in India

India is renowned for its complex megadiverse ecosystems and abundant biodiversity. Bovine tuberculosis (bTB) often remains synonymous with Mycobacterium bovis infection in cattle. The domain of tuberculosis (TB) among wild animals, induced by members of the Mycobacterium tuberculosis complex organisms (MTBC), is often underexplored and underreported in India. Within this context, instances of wild animal tuberculosis (wTB) have manifested across both captive and free-roaming animals. The sources contributing to wTB in animals can be human, animal, or environmental factors, thus illuminating the complex transmission pathways. The diagnosis of wTB continues to pose a formidable challenge, a consequence of the expansive taxonomic diversity in both the host and the pathogen. Complications inherent in acquiring samples from wildlife, the absence of standardized diagnostic protocols, limited insights into infection prevalence, and resource constraints compound diagnosis. Amidst these, adopting the comprehensive One Health paradigm surfaces as an imperative, accentuating the interconnectedness bridging human, animal, and environmental health. Recognizing key stakeholders and fostering intersectoral collaboration to provide enhanced diagnostic techniques driven by skilled personnel and advanced infrastructure play pivotal roles in a comprehensive strategy. Additionally, leveraging vaccination efforts contributes to effective control. A national wTB surveillance program is a cornerstone, ensuring an integrated and holistic approach to disease management. Through this review, we delve into the current landscape of wTB in India, unveiling its multifaceted challenges, and further explore the multifarious strategies that the One Health approach proffers in this dynamic endeavor.

Insight into the genetic diversity of Mycobacterium bovis isolated from cattle in Malawi

We describe the genetic diversity and phylogenetic relationships of Mycobacterium bovis, isolated from cattle in Malawi. Deletion analysis, spoligotyping, and MIRU-VNTR typing were used to genotype the isolates. Combined with a larger dataset from neighboring countries, the overall M. bovis diversity in Southern Africa was contextualized. From the southern and northern regions of Malawi, 24 isolates were confirmed as M. bovis. We pooled data for the central region (60 isolates) from our recent publication to conceptualize the genetic and phylogenetic relationships of M. bovis in Malawi. European 1 was the dominant M. bovis clonal complex, with 10 unique spoligotype patterns, and SB0131 was ubiquitous. High genetic diversity, a low clustering rate, and many singletons, coupled with a low mutation transmission index, infer a low level of recent transmission, and suggest an endemic status of bovine tuberculosis (bTB) in Malawi. M. bovis isolates from Zambia, Mozambique, and South Africa were genetically related to Malawian isolates, whereas Tanzanian isolates were distantly related. The diversity and phylogenetic analysis suggest earlier introductions and maintenance of M. bovis by constant reinfection from reservoir animals. These findings are fundamental to understanding the source and route of infection in order to establish alternative management strategies for bTB.

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.

Evidence, Challenges, and Knowledge Gaps Regarding Latent Tuberculosis in Animals

Mycobacterium bovis and other Mycobacterium tuberculosis complex (MTBC) pathogens that cause domestic animal and wildlife tuberculosis have received considerably less attention than M. tuberculosis, the primary cause of human tuberculosis (TB). Human TB studies have shown that different stages of infection can exist, driven by host–pathogen interactions. This results in the emergence of heterogeneous subpopulations of mycobacteria in different phenotypic states, which range from actively replicating (AR) cells to viable but slowly or non-replicating (VBNR), viable but non-culturable (VBNC), and dormant mycobacteria. The VBNR, VBNC, and dormant subpopulations are believed to underlie latent tuberculosis (LTB) in humans; however, it is unclear if a similar phenomenon could be happening in animals. This review discusses the evidence, challenges, and knowledge gaps regarding LTB in animals, and possible host–pathogen differences in the MTBC strains M. tuberculosis and M. bovis during infection. We further consider models that might be adapted from human TB research to investigate how the different phenotypic states of bacteria could influence TB stages in animals. In addition, we explore potential host biomarkers and mycobacterial changes in the DosR regulon, transcriptional sigma factors, and resuscitation-promoting factors that may influence the development of LTB.

Molecular epidemiology of Mycobacterium bovis in central parts of Malawi

Bovine tuberculosis (bTB) is a neglected disease that affects cattle and humans. The burden of bTB is higher in developing countries as compared to industrialized countries. The reasons behind this discrepancy include the fact that bTB control measures, such as testing and slaughter of infected cattle and pasteurization of milk, are not usually practised in developing countries largely because of their high cost. To improve our understanding of bTB in developing countries, molecular typing studies are essential, in particular in terms of transmission dynamics, infection sources and knowledge of circulating strains of the principal causative agent, Mycobacterium bovis. In this study, we applied a suite of molecular typing techniques encompassing deletion analysis, spoligotyping and MIRU-VNTR to isolates recovered from samples collected during the routine post-mortem of cattle at the cold storage abattoir in Lilongwe, Malawi. Out of 63 isolates, 51 (81%) belonged to the European 1. M. bovis clonal complex. Spoligotyping identified 8 profiles, with SB0131 being the predominant type (56% of isolates). Spoligotypes SB0273 and SB0425 were identified in 14% and 13%, respectively, of the isolates. MIRU-VNTR showed a high discriminatory power of 0.959 and differentiated the 8 spoligotypes to 31 genotypes. The high diversity of M. bovis within the study area suggests the infection has been circulating in the area for a considerable period of time, likely facilitated by the lack of effective control measures. We also observed genetic similarities between isolates from Malawi (this study) to isolates described in previous studies in Zambia and Mozambique, suggesting transmission links in this region. The information provided by this study provides much needed evidence for the formulation of improved bTB control strategies.

Development of a loop-mediated isothermal amplification (LAMP) method for specific detection of Mycobacterium bovis

Bovine tuberculosis (TB) caused by Mycobacterium bovis is a significant health threat to cattle and a zoonotic threat for humans in many developing countries. Rapid and accurate detection of M. bovis is fundamental for controlling the disease in animals and humans, and for the proper treatment of patients as one of the first-line anti-TB drug, pyrazinamide, is ineffective against M. bovis. Currently, there are no rapid, simplified and low-cost diagnostic methods that can be easily integrated for use in many developing countries. Here, we report the development of a loop-mediated isothermal amplification (LAMP) assay for specific identification of M. bovis by targeting the region of difference 4 (RD4), a 12.7 kb genomic region that is deleted solely in M. bovis. The assay's specificity was evaluated using 139 isolates comprising 65 M. bovis isolates, 40 M. tuberculosis isolates, seven M. tuberculosis complex reference strains, 22 non-tuberculous mycobacteria and five other bacteria. The established LAMP detected only M. bovis isolates as positive and no false positives were observed using the other mycobacteria and non-mycobacteria tested. Our LAMP assay detected as low as 10 copies of M. bovis genomic DNA within 40 minutes. The procedure of LAMP is simple with an incubation at a constant temperature. Results are observed with the naked eye by a color change, and there is no need for expensive equipment. The established LAMP can be used for the detection of M. bovis infections in cattle and humans in resource-limited areas.

Although bovine tuberculosis in humans has been eliminated in developed countries, the disease remains a challenge in many developing countries. Routine laboratory methods used to identify tuberculosis (TB) in high-burden countries do not distinguish between the two main causes of TB in humans, namely Mycobacterium tuberculosis and M. bovis. In addition, M. bovis is naturally resistant to one of the first-line drugs used to treat TB called pyrazinamide; therefore, accurate diagnosis of M. bovis is important for proper selection of anti TB drugs. In cattle, surveillance for M. bovis infection is important to obtain data on bovine TB burden and hence provide a basis for the establishment and/or improvement of control programs. In this study, a loop-mediated isothermal amplification (LAMP) based method was developed to identify M. bovis. This LAMP method detected M. bovis within 40 minutes following incubation at constant temperature (66°C) in a battery-powered incubator and results could be read with the naked eye following development of a color change. Our results elaborate a rapid and low-cost LAMP based method for detection and surveillance of M. bovis infection in cattle and humans in resource-limited, endemic areas.

Tracing cross species transmission of Mycobacterium bovis at the wildlife/livestock interface in South Africa

BACKGROUND

Bovine tuberculosis (bTB) affects cattle and wildlife in South Africa with the African buffalo (Syncerus caffer) as the principal maintenance host. The presence of a wildlife maintenance host at the wildlife/livestock interface acting as spill-over host makes it much more challenging to control and eradicate bTB in cattle. Spoligotyping and mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) genotyping methods were performed to investigate the genetic diversity of Mycobacterium bovis (M. bovis) isolates from cattle and wildlife, their distribution and transmission at the wildlife/livestock interface in northern Kwa-Zulu Natal (KZN), South Africa.

RESULTS

SB0130 was identified as the dominant spoligotype pattern at this wildlife/livestock interface, while VNTR typing revealed a total of 29 VNTR profiles (strains) in the KZN province signifying high genetic variability. The detection of 5 VNTR profiles shared between cattle and buffalo suggests M. bovis transmission between species. MIRU-VNTR confirmed co-infection in one cow with three strains of M. bovis that differed at a single locus, with 2 being shared with buffalo, implying pathogen introduction from most probably unrelated wildlife sources.

CONCLUSION

Our findings highlight inter and intra species transmission of bTB at the wildlife/livestock interface and the need for the implementation of adequate bTB control measures to mitigate the spread of the pathogen responsible for economic losses and a public health threat.

A first insight into the application of high discriminatory MIRU-VNTR typing using QIAxcel technology for genotyping Mycobacterium bovis isolated from the Delta area in Egypt

Mycobacterium bovis is a notorious infectious agent leading to serious economic losses for cattle farms worldwide. Analysis of the widely spreading genotypes is vital for tracing infections, understanding transmission dynamics, and controlling the cluster growth. This study aimed to evaluate the discrimination ability of 15 mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR) loci and to assess the extremely efficient loci subset for molecular epidemiological investigations of M.bovis from farms in the Delta area of Egypt. The discriminating ability of MIRU-VNTR genotyping using 15 loci {2 exact tandem repeat (ETR) loci, 6 MIRU loci, 4 Mtub loci, and 3 Queen's University of Belfast (QUB) group loci)} were evaluated on 61 M.bovis isolates from cattle (Holstein Frisian) and buffaloes. The results indicate that there are 48 genotypes: 3 unique genotypes and 45 genotypes with shared similarities. Using the MIRU-VNTRplus database, M.bovis ID 7540/01 and ID 5346/02 were the nearest lineages to both groups. Six loci (MIRU10, QUB11b, QUB26, ETRA, Mtub30, and Mtub39) were highly discriminating, seven other loci (Mtub21, MIRU26, QUB4156, MIRU04 (ETRD), MIRU16, MIRU 40, and ETRC) gave moderate discriminatory power, and the last two loci (Mtub04 and MIRU31) were poorly discriminative. MIRU-VNTR typing generally proved efficacy and high discriminatory power, with a collective allele's diversification of 0.9641. Both the six highly discriminating (DI = 0.9492) and the seven moderately discriminating loci (DI = 0.9269) evidenced to be suitable for M.bovis first-step initial genotyping from cattle herds in Egypt. MIRU-VNTR is rapid and effective in the genotyping of M.bovis from cattle and buffaloes in Egypt.

Epidemiology of Mycobacterium bovis and Mycobacterium tuberculosis in animals: Transmission dynamics and control challenges of zoonotic TB in Ethiopia

Mycobacterium tuberculosis complex is the cause of tuberculosis (TB) in humans and other animals. Specifically, Mycobacterium bovis (M. bovis) and Mycobacterium tuberculosis (M. tuberculosis) are highly pathogenic mycobacteria that may infect different animal species and are the sources of TB in humans. The objective of this paper was to review the epidemiology of M. bovis and M. tuberculosis in animals. The review also highlighted the transmission dynamics of M. bovis and M. tuberculosis in humans and animals and control challenges of zoonotic TB in Ethiopia. The literature review focused on scientific peer-reviewed articles from studies exclusively conducted in Ethiopia that were published from 1998 to 2017. Husbandry system, breed and herd size have significant role in the epidemiology of bovine tuberculosis (BTB) in Ethiopia. The information presented reveals that different strains of M. bovis are widely distributed in domestic animals predominantly in the Ethiopian cattle and the main strain was found to be SB1176. In addition, the isolation of M. tuberculosis from domestic animals in different settings signifies the circulation of the agent between humans and animals in Ethiopia. The life styles of the Ethiopian communities, close contact with domestic animals and/or the habit of consuming raw animal products, are suggested as the main factors for transmission of M. bovis and M. tuberculosis between human and animal which may have impact on the TB control program in human. In Ethiopia, a human TB control program has been widely implemented, however, the role of animal in the transmission of the causative agent has been neglected which could be one of the challenges for an effective control program. This warrants the need for incorporating animal TB control programs using "One Health" approach for effective TB control for both human and animal.

Genetic profiling of Mycobacterium bovis strains from slaughtered cattle in Eritrea

Mycobacterium bovis (M.bovis) is the main causative agent for bovine tuberculosis (BTB) and can also be the cause of zoonotic tuberculosis in humans. In view of its zoonotic nature, slaughterhouse surveillance, potentially resulting in total or partial condemnation of the carcasses and organs, is conducted routinely. Spoligotyping, VNTR profiling, and whole genome sequencing (WGS) of M. bovis isolated from tissues with tuberculosis-like lesions collected from 14 cattle at Eritrea’s largest slaughterhouse in the capital Asmara, were conducted.The 14 M. bovis isolates were classified into three different spoligotype patterns (SB0120, SB0134 and SB0948) and six VNTR profiles. WGS results matched those of the conventional genotyping methods and further discriminated the six VNTR profiles into 14 strains. Furthermore, phylogenetic analysis of the M. bovis isolates suggests two independent introductions of BTB into Eritrea possibly evolving from a common ancestral strain in Europe.This molecular study revealed the most important strains of M. bovis in Eritrea and their (dis)similarities with the strains generally present in East Africa and Europe, as well as potential routes of introduction of M. bovis. Though the sample size is small, the current study provides important information as well as platform for future in-depth molecular studies on isolates from both the dairy and the traditional livestock sectors in Eritrea and the region. This study provides information onthe origin of some of the M. bovis strains in Eritrea, its genetic diversity, evolution and patterns of spread between dairy herds. Such information is essential in the development and implementation of future BTB control strategy for Eritrea.

The livestock sector plays a major role in poverty and hunger reduction in the vast majority of Africa, as a source of food, cash income, manure, draught power, transportation, savings, insurance and social status. However, for livestock to play this vital role, the impact of diseases of economic and zoonotic importance need to be reduced. Bovine tuberculosis, mainly caused by Mycobacterium bovis, is such an infectious disease. Slaughterhouse (gross pathology) surveillance, followed by bacterial culture and genotyping, are options to identify the disease-causing agents, their distribution, and enabling trace back of the sources of infections, in order to prevent their re-introduction and spread. Unfortunately, genotyping is by far not generally introduced in the continent. In the present study, tissues with tuberculosis-like lesions were collected from the Asmara municipal slaughterhouse, the largest slaughterhouse in Eritrea, and bacterial culture, classical Mycobacterium tuberculosis complex typing (Spoligotyping and VNTR profiling), as well as whole genome sequencing (WGS) were used to gain insight into the spatial and temporal distribution, genetic diversity and evolution of M. bovis strains circulating in Eritrean dairy cattle. The results revealed (dis)similarities of the Eritrean M. bovis strains with the strains generally present in Africa and Europe, potential routes of introduction to Eritrea and genetic diversity of the M. bovis strains. Future in-depth molecular studies including more samples from dairy cattle as well as cattle and goats from the traditional livestock sector are recommended.

Genetic diversity and potential routes of transmission of Mycobacterium bovis in Mozambique

Bovine tuberculosis is a zoonotic disease with largely unknown impact in Africa, with risk factors such as HIV and direct contact with animals or consumption of Mycobacterium bovis infected animal products. In order to understand and quantify this risk and design intervention strategies, good epidemiological studies are needed. Such studies can include molecular typing of M. bovis isolates. The aim of this study was to apply these tools to provide novel information concerning the distribution of bovine tuberculosis in cattle in Mozambique and thereby provide relevant information to guide policy development and strategies to contain the disease in livestock, and reduce the risk associated with transmission to humans. A collection of 178 M. bovis isolates was obtained from cattle in Mozambique. Using spoligotyping and regions of difference analysis, we classified the isolates into clonal complexes, thus reporting the first characterisation of M. bovis strains in this region. Data from MIRU-VNTR typing was used to compare isolates from a number of African countries, revealing a deeply geographically structured diversity of M. bovis. Eastern Africa appears to show high diversity, suggesting deep evolution in that region. The diversity of M. bovis in Africa does not seem to be a function of recent importation of animals, but is probably maintained within each particular region by constant reinfection from reservoir animals. Understanding the transmission routes of M. bovis in Mozambique and elsewhere is essential in order to focus public health and veterinary resources to contain bovine tuberculosis.

Bovine tuberculosis is a rather neglected zoonotic disease caused by Mycobacterium bovis that is of global concern owing to the persistence of the bacillus in reservoirs that can spread bovine tuberculosis between animals and humans. Africa remains understudied regarding this pathogen, and should be an area of concern given that in many regions the consumption of raw milk or meat from infected animals persists and the presence of HIV infection renders the population more susceptible. In order to control the disease, we need to understand M. bovis epidemiology, which includes the sources of infection. The important conclusion drawn from the work presented here is that there is a strong association between M. bovis genetic characteristics and geography. This implies that the diversity of M. bovis isolates in Mozambique does not seem to be caused by recent introductions to the territory, but is probably maintained within reservoirs in each particular region.

Patterns and processes of Mycobacterium bovis evolution revealed by phylogenomic analyses

Mycobacterium bovis is an important animal pathogen worldwide that parasitizes wild and domesticated vertebrate livestock as well as humans. A comparison of the five M. bovis complete genomes from the United Kingdom, South Korea, Brazil, and the United States revealed four novel large-scale structural variations of at least 2,000 bp. A comparative phylogenomic study including 2,483 core genes of 38 taxa from eight countries showed conflicting phylogenetic signal among sites. By minimizing this effect, we obtained a tree that better agrees with sampling locality. Results supported a relatively basal position of African strains (all isolated from Homo sapiens ), confirming that Africa was an important region for early diversification and that humans were one of the earliest hosts. Selection analyses revealed that functional categories such as “Lipid transport and metabolism,” “Cell cycle control, cell division, chromosome partitioning” and “Cell motility” were significant for the evolution of the group, besides other categories previously described, showing importance of genes associated with virulence and cholesterol metabolism in the evolution of M. bovis . PE/PPE genes, many of which are known to be associated with virulence, were major targets for large-scale polymorphisms, homologous recombination, and positive selection, evincing for the first time a plethora of evolutionary forces possibly contributing to differential adaptability in M. bovis . By assuming different priors, US strains originated and started to diversify around 150–5,210 ya. By further analyzing the largest set of US genomes to date (76 in total), obtained from 14 host species, we detected that hosts were not clustered in clades (except for a few cases), with some faster-evolving strains being detected, suggesting fast and ongoing reinfections across host species, and therefore, the possibility of new bovine tuberculosis outbreaks.

Evaluation of MIRU-VNTR for typing of Mycobacterium bovis isolated from Sika deer in Northeast China

Background

Bovine tuberculosis has led to serious economic losses for Sika Deer producers in China. Strategies for controlling the spread of Mycobacterium bovis are often hampered by a lack of epidemiological data. Specifically, tracing infections requires the ability to trace back infections, which, in turn, requires the ability to determine isolates with a common source. This study was planned to assess the discriminatory power of each mycobacterial interspersed repetitive unit (MIRU)-variable number tandem repeats (VNTR) locus and evaluate the most appropriate combination of MIRU-VNTR loci for molecular epidemiological studies on Sika Deer in China.

Results

The discriminatory power of MIRU-VNTR typing based on 22 known loci (12 MIRUs, 2 ETRs, 4 QUBs, and 4 Mtubs) were assessed in 96 Mycobacterium bovis strains collected sequentially from Sika Deer at a slaughterhouse in northeastern China. We defined four loci (MIRU4, ETRA, QUB11b, and Mtub4) as highly discriminative, eight loci (MIRU2, MIRU23, MIRU27, MIRU31, MIRU39, MIRU40, QUB26, and Mtub21) as moderately discriminative, and three loci (MIRU16, Mtub30, and Mtub34) as poorly discriminative. The final locus showed no polymorphism between strains. MIRU-VNTR typing as a whole was highly discriminative, with an overall allelic diversity of 0.897. Of the loci tested, the four highly discriminative loci and eight moderately discriminative loci proved to be most appropriate for first line typing of M. bovis from Sika Deer, with the same resolving ability as all 22 loci (H = 0.897).

Conclusions

MIRU-VNTR typing is quick and effective for typing bovine tuberculosis isolates from Sika Deer in China.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0402-0) contains supplementary material, which is available to authorized users.

Isolation and molecular characterization of Mycobacterium bovis from Kafue lechwe (Kobus leche kafuensis) from Zambia

Bovine tuberculosis (BTB) is a chronic bacterial disease caused by Mycobacterium bovis. Infections due to M. bovis, which serves as a stable reservoir, can pose serious challenge to control and eradicate in both wildlife and livestock at the interface. This study aimed at isolating and characterizing M. bovis from Kafue lechwe (Kobus leche kafuensis) and black lechwe (Kobus leche smithemani) at the animal/human interface in Zambia. The samples with lesions compatible with BTB collected during the hunting seasons of 2009 and 2010 were cultured for isolation of mycobacteria using Stonebrink with pyruvate (BD Diagnostics, MD, USA) and Middlebrook 7H10 (BD Diagnostics) slants. Isolated mycobacteria were identified using IS6110 polymerase chain reaction and deletion analysis. Molecular characterization of the isolates was performed using spoligotyping and mycobacteria interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) with nine loci. Data was analyzed using BioNumerics software 6.1. Out of the 39 samples, acid fast bacilli were detected in 27 (69.2 %) based on smear microscopy. Seven isolates were found to belong to Mycobacterium tuberculosis complex, and all were identified as M. bovis based on deletion analysis. All seven isolates were identical on spoligotyping as belonging to the SB0120 (SIT 482). MIRU-VNTR differentiated the isolates into five different patterns. This study has confirmed that M. bovis circulates in the Kafue lechwe, and non-tuberculous mycobacteria were detected in the black lechwe in Zambia which represents a wildlife reservoir, with a potential to spillover to cattle and humans. Isolates of M. bovis from lechwe antelopes are much conserved as only one spoligotype was detected. The study has shown that three loci differentiated fairly well. This option is cheap and less laborious, and hence a better option in resource-strained country like Zambia. The study further showed that some of the loci recommended by the European Reference Laboratory are not suitable for typing M. bovis in Zambia.

An epidemiological perspective on bovine tuberculosis spotlighting facts and dilemmas in Iran, a historically zebu-dominant farming country

For the whole 20th century, bovine tuberculosis (BTB) challenged the international community efforts to control this zoonotic disease. Asia and Africa accommodate the largest BTB-infected zebu cattle in the world. Similar to other few Asian nations, Iran has been actively running its BTB-control plan for the last four decades. BTB however, is still a number-one health concern for Iranian veterinary practitioners and also farmers across the country. Why is that? Here we have addressed this question in the light of most recent epidemiological data as well as microbiology and molecular biology observations.