Bovine tuberculosis in India: Potential basis for zoonosis

doi:10.1016/j.tube.2005.08.005

Tuberculosis

Volume 85, Issues 5–6, September–November 2005, Pages 421-428

https://doi.org/10.1016/j.tube.2005.08.005 Get rights and content

Summary

Our laboratory has designed a specific nested-PCR (N-PCR) assay, based on the hupB gene of Mycobacterium tuberculosis (Rv2986c) and Mycobacterium bovis (Mb3010c) as a method to differentiate these closely related species. The present paper deciphers the utility of this assay for identification of pathogenic Mycobacteria in clinical samples. Extra-pulmonary clinical samples obtained from cattle and humans were investigated. Pre-dominance of M. tuberculosis (15.7%) and M. bovis (26.8%) was seen in humans and cattle, respectively. However, more importantly, both mycobacterial pathogens (mixed infection) were identified in a number of samples. In humans 8.7% of the samples and 35.7% in cattle were classified as mixed infection. The detection of mixed infection with the mycoabcterial pathogenic duo in humans and bovines denotes the prospect of potential transmission of these pathogens from humans to cattle (zoonosis) and vice versa (reverse zoonosis).

Introduction

Infection with Mycobacterium bovis and Mycobacterium tuberculosis have been known to cause bovine and human tuberculosis, respectively.1, 2, 3 The reported increase in incidence of infection by these two species in domesticated animals and humans has become the subject of investigation. However, there are reports that these mycobacterial pathogens are not limited to these susceptible hosts. In fact infection with M. tuberculosis and M. bovis has shown to occur across a wide spectrum of species.4, 5 In developing countries, increase of M. bovis infection in humans has manifested into a grave public health problem.6, 7, 8 This crisis has been related to the fact that in developing countries domesticated animals and humans share the same habitat.⁹ The problem has been further exacerbated by reports of: (i) transmission to animals from humans shedding infectious tubercle bacilli10, 11; and (ii) the association of HIV with M. bovis besides M. tuberculosis.12, 13, 14

The disease caused by M. bovis is indistinguishable to that caused by M. tuberculosis.¹⁵ The bacteriological, biochemical and genetic similarities of these two species have made it difficult to differentially identify them in clinical samples/cultivated isolates. Presently, a battery of tedious tests (microbiological, biochemical, etc.) has been described for detecting and differentiating M. tuberculosis and M. bovis. In the recent past there have been reports of molecular biological techniques such as multiplex-PCR and spoligotyping for differentiating these two mycobacterial species.16, 17, 18, 19, 20, 21

Our laboratory has designed a reliable and specific, PCR-RFLP and nested-PCR (N-PCR) assays to differentiate and detect these species in clinical isolates and samples.22, 23, 24 The assay exploits the 27 bp difference in the C-terminal part of the hupB gene between M. tuberculosis and M. bovis (Rv2986c in M. tuberculosis; Mb3010c in M. bovis).²² Further, the utility of the PCR target in identifying mixed infection with these closely related pathogens namely M. tuberculosis and M. bovis in an individual sample has been demonstrated.23, 24 The degree of correlation between the gold standard culture-based identification techniques and PCR-RFLP assay has been shown to be 99.0% ( $p < 0.001$ ).²³ The present paper summarizes some of our work on the detection and differentiation of the two pathogens in extra-pulmonary samples of bovine and human origin.

Section snippets

Animals

Fifty-six cattle of a single herd were segregated into two groups. One group consisting of 29 cattle with signs and symptoms of tuberculosis (TB category) and the second, 27 healthy animals clinically free of tuberculosis (NTB category). Clinical examination of the cattle was carried out at Central Military Veterinary Laboratory, Meerut. Samples were processed in the laboratories of HKP for N-PCR for detection of pathogenic Mycobacteria and VMK for cultivation and characterization by standard

Detection and differentiation of M. bovis and M. tuberculosis in cattle by N-PCR assay

Bovine samples obtained from the two categories of cattle viz. tuberculous (TB) and not categorized as tuberculous (NTB), were processed for N-PCR as described in methods. The amplified products obtained in representative bovine samples have been shown in Fig. 2. The mycobacterial pathogens in the cattle were identified as M. tuberculosis and M. bovis based on gel analysis. The molecular weights of the N-PCR products obtained for standard M. tuberculosis and M. bovis corresponded to 116 and 89

Discussion

Bovine tuberculosis, caused by M. bovis, has been on the increase in developed countries and continues to occur in developing countries.3, 6 The epidemiological impact of M. bovis infection in humans has not been assessed and is a major lacuna in developing countries. M. bovis has been known to spread to humans from infected cattle (zoonotic TB) by aerosol or by consumption of contaminated dairy products (Fig. 5).1, 6 Tuberculosis caused by M. bovis is clinically indistinguishable from that

Acknowledgments

The role of Dr. J.S. Tyagi during the execution of the project is acknowledged. This work was supported by Department of Biotechnology (DBT) India. A.S. was a recipient of SRF fellowship from University Grant Commission (UGC) India.

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Bovine tuberculosis in India: The need for One Health approach and the way forward
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Bovine tuberculosis (bTB) is a chronic granulomatous infectious illness in cattle. The etiological agent of bTB is Mycobacterium bovis. However, other members belonging to the Mycobacterium tuberculosis complex, like M. tuberculosis, M. africanum, M. caprae, M. orygis, and M. microti are known to cause bTB in cattle. There are 303.76 million bovines in India, and it is the largest producer of milk and the second largest producer of meat worldwide. The prevalence of bTB among farm and dairy cattle in India is estimated to be around 7.3%, which makes it a country with one of the largest infected herds in the world. While bTB control programs have had considerable success in reducing the prevalence of the disease in many developed countries, they have yet to be formulated or implemented in India. Bovine TB also has a zoonotic and reverse component, which means that the disease can spread from cattle to human and from human to cattle. In a country like India, which contributes to nearly one-fourth of the global TB burden, the zoonotic aspect must be addressed so that the disease can be curbed. While cattle are the primary reservoir host to bTB, animals like goats, deer, bison, pigs, dogs, badgers, possums, and primates are also susceptible to the disease. This review talks about the burden of bTB in India and the necessity of One Health approach to combat the disease.
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Citation Excerpt :
M. bovis, a globally distributed bacilli and the main cause of bovine TB, also infects humans, domestic animal species, and wildlife [12]. M. tuberculosis is primarily a human pathogen and is isolated only from domestic and wildlife species that have lived in close proximity to humans for an extended period of time [13]. In recent years, M. orygis has emerged as a cause of zoonotic TB, especially in South Asia [14].
Tuberculosis (TB) is a serious zoonotic threat, impacting the human-livestock-wildlife interface globally. Here, we evaluated the status and histomorphological differentiation of TB lesions in 89 morbid cases of wild animals (bovids, cervids, carnivores, non-human primates, and pachyderms) in India. Histomorphological and molecular studies were done using Ziehl-Neelsen (ZN) staining, immunohistochemistry, and polymerase chain reaction (PCR), whereas cultural isolation was performed on selected samples. A total of 32 (35.95%) cases were confirmed as TB, comprising of 12 carnivores, 09 bovids, 06 cervids, 04 non-human primates, and a pachyderm. The TB lesions in the lungs, liver, and lymph nodes varied from the large-sized caseous nodules filled with dry cheesy material in bovids and cervids to variable-sized cavitations containing liquefied caseum in carnivores' lungs. The lungs, livers, and spleens of non-human primates exhibited small to medium-sized nodules. Histologically, lesions were divided into four categories (Types I, II, III, and IV) based on the extent of necrosis, the presence of mineralization, giant cells, and fibrous encapsulation. Extensive caseous necrosis with calcification, abundant giant cells, and thick fibroblastic encapsulation were consistent findings in the lungs, livers, and lymph nodes of bovids and cervids, whereas airway impaction with cellular exudate containing a teeming number of acid-fast bacilli and, at times, alveolar rupture leading to cavity formation was present in the lungs of carnivores. Absence of calcification and fibrous encapsulation was recorded in lungs of non-human primates. Immunohistochemical labelling with anti-early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10) antibodies showed mild, moderate, and intense positive reactions in type II and III, type I, and type IV granulomatous lesions, respectively. Molecular detection by PCR revealed Mycobacterium tuberculosis (12 carnivores, 02 non-human primates and 01 pachyderm), M. bovis (02 cervids and 01 bovid) and M. orygis (02 cervids and 01 bovid). Cultural isolation confirmed M. tuberculosis in 03 carnivores and M. orygis in 02 cervids and 01 bovid. Our findings imply that TB is quite prevalent in the wildlife of India and there are considerable differences in the histomorphological lesions induced by distinct Mycobacterium species in different wild animals. The circulation of TB organisms in wild animals warrants a strict surveillance programme to identify the carrier status of these animals so that effective TB control strategies can be formulated to prevent spillover and spillback incidences at the human-livestock-wildlife interface.
Reconsidering Mycobacterium bovis as a proxy for zoonotic tuberculosis: a molecular epidemiological surveillance study
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Zoonotic tuberculosis is defined as human infection with Mycobacterium bovis. Although globally, India has the largest number of human tuberculosis cases and the largest cattle population, in which bovine tuberculosis is endemic, the burden of zoonotic tuberculosis is unknown. The aim of this study was to obtain estimates of the human prevalence of animal-associated members of the Mycobacterium tuberculosis complex (MTBC) at a large referral hospital in India.
We did a molecular epidemiological surveillance study of 940 positive mycobacteria growth indicator tube (MGIT) cultures, collected from patients visiting the outpatient department at Christian Medical College (Vellore, India) with suspected tuberculosis between Oct 1, 2018, and March 31, 2019. A PCR-based approach was applied to subspeciate cultures. Isolates identified as MTBC other than M tuberculosis or as inconclusive on PCR were subject to whole-genome sequencing (WGS), and phylogenetically compared with publicly available MTBC sequences from south Asia. Sequences from WGS were deposited in the National Center for Biotechnology Information Sequence Read Archive, accession number SRP226525 (BioProject database number PRJNA575883).
The 940 MGIT cultures were from 548 pulmonary and 392 extrapulmonary samples. A conclusive identification was obtained for all 940 isolates; wild-type M bovis was not identified. The isolates consisted of M tuberculosis (913 [97·1%] isolates), Mycobacterium orygis (seven [0·7%]), M bovis BCG (five [0·5%]), and non-tuberculous mycobacteria (15 [1·6%]). Subspecies were assigned for 25 isolates by WGS, which were analysed against 715 MTBC sequences from south Asia. Among the 715 genomes, no M bovis was identified. Four isolates of cattle origin were dispersed among human sequences within M tuberculosis lineage 1, and the seven M orygis isolates from human MGIT cultures were dispersed among sequences from cattle.
M bovis prevalence in humans is an inadequate proxy of zoonotic tuberculosis. The recovery of M orygis from humans highlights the need to use a broadened definition, including MTBC subspecies such as M orygis, to investigate zoonotic tuberculosis. The identification of M tuberculosis in cattle also reinforces the need for One Health investigations in countries with endemic bovine tuberculosis.
Bill & Melinda Gates Foundation, Canadian Institutes for Health Research.
A review on bovine tuberculosis in India
2020, Tuberculosis
Bovine tuberculosis (bTB) is a chronic illness in animals, especially in cattle, leading to loss in the productivity and signifies a crucial public health risk. Regardless of the zoonotic threat and significant economic costs associated with the disease, precise estimates of bTB prevalence are deficient in many countries, including India, where national control programs are yet to be instigated. The true burden of the disease remains unknown due to lack of routine surveillance data from most of the developing countries. India is progressing well towards attaining the End TB goal, yet bTB continues to remain largely hidden. Moreover, the paucity of literature on bTB in India might lead to undue complacency and hence has to be scrupulously guarded and prevented from gaining any misconceptions in the minds of the common people. Preventing and controlling bTB at the animal interface is pivotal to evade transmission to human, increase food safety and guard the livelihood of the people. To attain this goal, implementation of strategies based on international norms and a multi-sectoral approach will empower enhanced surveillance and diagnosis of disease in animals and subsequently reduce the risk for humans. As an initiative, we step forward to address this review which briefly summarizes the available data in the literature from early 20th century to date to assess the status of bTB in India. We have discussed in detail, the epidemiology, transmission and diagnosis pertaining to bTB. The review also focuses on the interconnection between the health of people and animal, discuss the preventions and control strategies and recommend the use of vaccination in cattle to reduce the spread of infection among other animals and humans. Implementing One Health approach in India, which recognizes the interdependence of the health of people and animals will help the nation in the fight against TB.
Conventional and molecular determination of drug resistance in Mycobacterium tuberculosis and Mycobacterium bovis isolates in cattle
2019, Tuberculosis
This study was aimed out to explore the presence of drug resistance among M. tuberculosis and M. bovis isolates (n = 51) of bovine origin by conventional broth microdilution method and molecular methods. By broth microdilution method, 16 isolates were found to be resistant to isoniazid, 08 isolates were resistant to pyrazinamide, 09 isolates were resistant to rifampicin and 07 isolates were found to be resistant for ethambutol. Two isolates showed resistance to rifampicin and pyrazinamide, one isolate showed resistance to pyrazinamide and ethambutol and 03 isolates showed resistance to isoniazid and ethambutol. None of isolates showed multi drug resistance (MDR). Other than the M. bovis strains, none of the other M. tuberculosis isolates showed any resistance to pyrazinamide. Molecular methods by multiplex PCR targeting katG, pncA, rpoB genes, multiplex allele specific PCR to detect mutation in embB codon 306 and sequencing showed point mutation in katG and rpoB gene. No mutation could be detected in the embB gene by multiplex allele specific PCR. The results indicates that further elaborate studies need to be carried out due to the presence of drug resistant M. tuberculosis in bovines which could be due to spill over from human in tuberculosis endemic areas making TB eradication programme more challenging.
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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.

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¹: Present address: Section of Experimental Haematology/Oncology, Department of Paediatric Haematology/Oncology, Medical School Hanover, Carl Neuberg Strasse 1, D-30625 Hanover, Germany.

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Bovine tuberculosis in India: Potential basis for zoonosis

Summary

Introduction

Section snippets

Animals

Detection and differentiation of M. bovis and M. tuberculosis in cattle by N-PCR assay

Discussion

Acknowledgments

Tuber Lung Dis

Tuberculosis

Tuberculosis

Vet Microbiol

FEMS Microbiol Lett

Vet Microbiol

FEMS Microbiol Lett

Mycobacterium tuberculosis in zoo and wildlife species

Rev Sci Tech

Incidence of bovine tuberculosis in wild and domestic animals other than cattle in six Central European countries during 1990–1999

Vet Med Czech

Zoonotic tuberculosis due to Mycobacterium bovis in developing countries

Emerg Infect Dis

Tuberculosis due to Mycobacterium bovis in the Australian population: DNA typing of isolates, 1970–1994

Int J Tuberc Lung Dis

Isolation of Mycobacterium bovis from human cases of cervical adenitis in Tanzania: a cause for concern?

Int J Tuberc Lung Dis

Bovine tuberculosis: an old disease but a new threat to Africa

Int J Tuberc Lung Dis

Mycobacterium bovis tuberculosis: from animal to man and back

Int J Tuberc Lung Dis