Mycobacterium tuberculosis infections in eight species at the National Zoological Gardens of South Africa, 1991-2001

Granulomatous meningoencephalitis and blindness associated with Mycobacterium tuberculosis complex infection in a senile female chimpanzee (Pan troglodytes)

A 40-year old female chimpanzee (Pan troglodytes) developed hyporexia, weight loss, followed by progressive and complete blindness. Tomography demonstrated an intracranial mass in the rostroventral brain involving the optic chiasm, with a presumptive diagnosis of neoplasm. However, histopathology revealed a granulomatous meningoencephalitis, and tissue samples tested positive for Mycobacterium tuberculosis.

Mycobacterium tuberculosis sensu stricto in African Apes, What Is Its True Health Impact?

Since the Symposium on Mycobacterial Infections of Zoo Animals held at the National Zoological Park, Smithsonian Institution in 1976, our understanding of tuberculosis (TB) in non-domestic animals has greatly expanded. Throughout the past decades, this knowledge has resulted in improved zoo-habitats and facilities design, stricter biosecurity measures, and advanced diagnostic methods, including molecular techniques, that have significantly decreased the number of clinical disease caused by Mycobacterium tuberculosis in apes under human care settings. In the other hand, exponential growth of human populations has led to human encroachment in wildlife habitat which has resulted in increased inter-species contact and recurrent conflict between humans and wild animals. Although it is widely accepted that non-human primates are susceptible to M. tb infection, opinions differ with regard to the susceptibility to develop disease amongst different taxa. Specifically, some authors suggest that African apes are less susceptible to clinical tuberculosis than other species of primates. The aim of this review article is to evaluate the current scientific literature to determine the actual health impact of disease caused by Mycobacterium tuberculosis and more specifically Mycobacterium tuberculosis sensu stricto in African apes. The literature review included literature databases: Web of Science, Pubmed, Scopus, Wiley, Springer and Science direct, without temporal limit and proceedings of annual conferences in the field of wildlife health. Our general inclusion criteria included information about serological, molecular, pathological (macroscopic and/or microscopic), and clinical evidence of TB in African apes; while our, our more stringent inclusion selection criteria required that in addition to a gross pathology, a molecular test confirmed Mycobacterium tuberculosis sensu stricto as the cause of disease or death. We identified eleven reports of tuberculosis in African apes; of those, only four reports met the more stringent selection criteria that confirmed M. tb sensu stricto in six individuals. All reports that confirmed M. tb sensu stricto originated from zoological collections. Our review suggests that there is little evidence of disease or mortality caused by M. tb in the different species of African apes both under human care and free ranging populations. Additional studies are needed in free-ranging, semi-captive populations (sanctuaries) and animals under human care (zoos and rescue centers) to definitely conclude that this mycobacteria has a limited health effect in African ape species.

Infectious Disease Risk Across the Growing Human-Non Human Primate Interface: A Review of the Evidence

Most of the human pandemics reported to date can be classified as zoonoses. Among these, there is a long history of infectious diseases that have spread from non-human primates (NHP) to humans. For millennia, indigenous groups that depend on wildlife for their survival were exposed to the risk of NHP pathogens' transmission through animal hunting and wild meat consumption. Usually, exposure is of no consequence or is limited to mild infections. In rare situations, it can be more severe or even become a real public health concern. Since the emergence of acquired immune deficiency syndrome (AIDS), nobody can ignore that an emerging infectious diseases (EID) might spread from NHP into the human population. In large parts of Central Africa and Asia, wildlife remains the primary source of meat and income for millions of people living in rural areas. However, in the past few decades the risk of exposure to an NHP pathogen has taken on a new dimension. Unprecedented breaking down of natural barriers between NHP and humans has increased exposure to health risks for a much larger population, including people living in urban areas. There are several reasons for this: (i) due to road development and massive destruction of ecosystems for agricultural needs, wildlife and humans come into contact more frequently; (ii) due to ecological awareness, many long distance travelers are in search of wildlife discovery, with a particular fascination for African great apes; (iii) due to the attraction for ancient temples and mystical practices, others travelers visit Asian places colonized by NHP. In each case, there is a risk of pathogen transmission through a bite or another route of infection. Beside the individual risk of contracting a pathogen, there is also the possibility of starting a new pandemic. This article reviews the known cases of NHP pathogens' transmission to humans whether they are hunters, travelers, ecotourists, veterinarians, or scientists working on NHP. Although pathogen transmission is supposed to be a rare outcome, Rabies virus, Herpes B virus, Monkeypox virus, Ebola virus, or Yellow fever virus infections are of greater concern and require quick countermeasures from public health professionals.

Analysing nonsynonymous mutations between two Mycobacterium bovis strains with contrasting pathogenic profiles

Mycobacterium bovis (M. bovis) is the causative agent of bovine tuberculosis, a chronic infectious disease that can affect cattle, other domesticated species, wild animals and humans. This disease produces important economic losses worldwide. Two M. bovis strains (04-303 and 534) have been isolated in Argentina. Whereas the 04-303 strain was isolated from a wild boar, the 534 strain was obtained from cattle. In a previous study, six weeks after infection, the 04-303 strain induced 100% mortality in mice. By contrast, mice infected with the 534 strain survived, with limited tissue damage, after four months. In this study we compared all predictive proteins encoded in both M. bovis genomes. The comparative analysis revealed 141 polymorphic proteins between both strains. From these proteins, nine virulence proteins showed polymorphisms in 04-303, whereas five did it in the 534 strain. Remarkably, both strains contained a high level of polymorphism in proteins related to phthiocerol dimycocerosate (PDIM) synthesis or transport. Further experimental evidence indicated that only mutations in the 534 strain have an impact on PDIM synthesis. The observed reduction in PDIM content in the 534 strain, together with its low capacity to induce phagosome arrest, may be associated with the reported deficiency of this strain to replicate and survive inside bovine macrophages. The findings of this study could contribute to a better understanding of pathogenicity and virulence aspects of M. bovis, which is essential for further studies aiming at developing new vaccines and diagnostic techniques for bovines.

Fatal Tuberculosis in a Free-Ranging African Elephant and One Health Implications of Human Pathogens in Wildlife

Tuberculosis (TB) in humans is a global public health concern and the discovery of animal cases of Mycobacterium tuberculosis (Mtb) infection and disease, especially in multi-host settings, also has significant implications for public health, veterinary disease control, and conservation endeavors. This paper describes a fatal case of Mtb disease in a free-ranging African elephant (Loxodonta africana) in a high human TB burden region. Necropsy revealed extensive granulomatous pneumonia, from which Mtb was isolated and identified as a member of LAM3/F11 lineage; a common lineage found in humans in South Africa. These findings are contextualized within a framework of emerging Mtb disease in wildlife globally and highlights the importance of the One Health paradigm in addressing this anthroponotic threat to wildlife and the zoonotic implications.

Mycobacterium tuberculosis infection in cattle from the Eastern Cape Province of South Africa

Background

Mycobacterium tuberculosis is the main causative agent of tuberculosis (TB) in human and Mycobacterium bovis commonly causes tuberculosis in animals. Transmission of tuberculosis caused by both pathogens can occur from human to animals and vice versa.

Results

In the current study, M. tuberculosis, as confirmed by polymerase chain reaction (PCR) using primers targeting 3 regions of difference (RD4, RD9 and RD12) on the genomes, was isolated from cattle originating from two epidemiologically unrelated farms in the Eastern Cape (E.C) Province of South Africa. Although the isolates were genotyped with variable number of tandem repeat (VNTR) typing, no detailed epidemiological investigation was carried out on the respective farms to unequivocally confirm or link humans as sources of TB transmission to cattle, a move that would have embraced the ‘One Health’ concept. In addition, strain comparison with human M. tuberculosis in the database from the E.C Province and other provinces in the country did not reveal any match.

Conclusions

This is the first report of cases of M. tuberculosis infection in cattle in South Africa. The VNTR profiles of the M. tuberculosis strains identified in the current study will form the basis for creating M. tuberculosis VNTR database for animals including cattle for future epidemiological studies. Our findings however, call for urgent reinforcement of collaborative efforts between the veterinary and the public health services of the country.

Experimental Mycobacterium bovis infection in three white rhinoceroses (Ceratotherium simum): Susceptibility, clinical and anatomical pathology

Tuberculosis caused by Mycobacterium bovis is endemic in the African buffalo (Syncerus caffer) population in the Kruger National Park and other conservation areas in South Africa. The disease has been diagnosed in a total of 21 free ranging or semi-free ranging wildlife species in the country with highly variable presentations in terms of clinical signs as well as severity and distribution of tuberculous lesions. Most species are spillover or dead-end hosts without significant role in the epidemiology of the disease. White rhinoceroses (Ceratotherium simum) are translocated from the Kruger National Park in substantial numbers every year and a clear understanding of their risk to manifest overt tuberculosis disease and to serve as source of infection to other species is required. We report the findings of experimental infection of three white rhinoceroses with a moderately low dose of a virulent field isolate of Mycobacterium bovis. None of the animals developed clinical signs or disseminated disease. The susceptibility of the white rhinoceros to bovine tuberculosis was confirmed by successful experimental infection based on the ante mortem isolation of M. bovis from the respiratory tract of one rhinoceros, the presence of acid-fast organisms and necrotizing granulomatous lesions in the tracheobronchial lymph nodes and the detection of M. bovis genetic material by PCR in the lungs of two animals.

Detection of Mycobacterium tuberculosis Complex in New World Monkeys in Peru

The Mycobacterium tuberculosis complex causes tuberculosis in humans and nonhuman primates and is a global public health concern. Standard diagnostics rely upon host immune responses to detect infection in nonhuman primates and lack sensitivity and specificity across the spectrum of mycobacterial infection in these species. We have previously shown that the Oral Swab PCR (OSP) assay, a direct pathogen detection method, can identify the presence of M. tuberculosis complex in laboratory and free-ranging Old World monkeys. Addressing the current limitations in tuberculosis diagnostics in primates, including sample acquisition and pathogen detection, this paper furthers our understanding of the presence of the tuberculosis-causing bacteria among New World monkeys in close contact with humans. Here we use the minimally invasive OSP assay, which includes buccal swab collection followed by amplification of the IS6110 repetitive nucleic acid sequence specific to M. tuberculosis complex subspecies, to detect the bacteria in the mouths of Peruvian New World monkeys. A total of 220 buccal swabs from 16 species were obtained and positive amplification of the IS6110 sequence was observed in 30 (13.6%) of the samples. To our knowledge, this is the first documentation of M. tuberculosis complex DNA in a diverse sample of Peruvian Neotropical primates.

Bronchoalveolar lavage (BAL) in tapirs (Tapirus terrestris) with Mycobacterium tuberculosis

This paper describes the in vivo Bronchoalveolar lavage (BAL) technique by endoscopy in tapirs (Tapirus terrestris) with clinical signs of tuberculosis. The technique was performed in two tapirs, male and female, from Curitiba Zoo, Paraná, Brazil. A flexible endoscope and a polyethylene catheter were used after the chemical restraint of the animals. For BAL technique, 60mL of saline 0.9% were infused with a polyethylene catheter, introduced by the endoscope's working channel, and 15mL of BAL were recovered, analyzed and submitted to cytocentrifugation. Slides were stained by Papanicolaou, periodic acid-Schiff (PAS) and Ziehl-Neelsen methods contained high quantity of inflammatory cells on light microscopy (macrophages 27.5%, lymphocytes 0.5%, neutrophis 67% and eosinophis 5%). BAL samples were submitted to culture, bacilloscopy and PCR and were negative for both animals. Based on this study, it was concluded that the bronchoalveolar lavage technique in tapirs is feasible, simple, noninvasive, practical and fast, providing an important clinical information in vivo regarding the functional status of the lower respiratory tract.

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.

Mycobacterium tuberculosis at the human/wildlife interface in a high TB burden country

This study reports on an investigation of Mycobacterium tuberculosis cases in mostly captive wild animals using molecular typing tools [Variable Number of Tandem Repeat (VNTR) typing and Restriction Fragment Length Polymorphism typing]. The investigation included cases from (i) the National Zoological Gardens of South Africa (NZG) recorded between 2002 and 2011; (ii) Johannesburg Zoo, where tuberculosis was first diagnosed in 2007 and has since been detected in three antelope species; (iii) a rehabilitation centre for vervet monkeys (Chlorocebus pygerythrus) in which M. tuberculosis was diagnosed in 2008; and (iv) incidental cases in other facilities including a sable antelope (Hippotragus niger), two unrelated cases in chacma baboons (Papio ursinus) (one of which was from a free-ranging troop) and a colony of capuchin monkeys (Cebus capucinus). Identical genetic profiles of the latter three isolates indicate the persistence of a single M. tuberculosis strain in this population since at least 2006. Results of the outbreak investigation in the captive vervet monkey colony indicate that it was caused by two unrelated strains, while all 13 M. tuberculosis isolates from 11 animal species in the NZG showed different VNTR patterns. A substantial increase in tuberculosis cases of 60% was recorded in the NZG, compared with the previous reporting period 1991-2001, and may indicate a countrywide trend of increasing spillover of human tuberculosis to wild animals. South Africa ranks among the countries with the highest-tuberculosis burden worldwide, complicated by an increasing rate of multidrug-resistant strains. Exposure and infection of captive wildlife in this high prevalence setting is therefore a growing concern for wildlife conservation but also for human health through potential spillback.

Reverse zoonotic disease transmission (zooanthroponosis): a systematic review of seldom-documented human biological threats to animals

Background

Research regarding zoonotic diseases often focuses on infectious diseases animals have given to humans. However, an increasing number of reports indicate that humans are transmitting pathogens to animals. Recent examples include methicillin-resistant Staphylococcus aureus, influenza A virus, Cryptosporidium parvum, and Ascaris lumbricoides. The aim of this review was to provide an overview of published literature regarding reverse zoonoses and highlight the need for future work in this area.

Methods

An initial broad literature review yielded 4763 titles, of which 4704 were excluded as not meeting inclusion criteria. After careful screening, 56 articles (from 56 countries over three decades) with documented human-to-animal disease transmission were included in this report.

Findings

In these publications, 21 (38%) pathogens studied were bacterial, 16 (29%) were viral, 12 (21%) were parasitic, and 7 (13%) were fungal, other, or involved multiple pathogens. Effected animals included wildlife (n = 28, 50%), livestock (n = 24, 43%), companion animals (n = 13, 23%), and various other animals or animals not explicitly mentioned (n = 2, 4%). Published reports of reverse zoonoses transmission occurred in every continent except Antarctica therefore indicating a worldwide disease threat.

Interpretation

As we see a global increase in industrial animal production, the rapid movement of humans and animals, and the habitats of humans and wild animals intertwining with great complexity, the future promises more opportunities for humans to cause reverse zoonoses. Scientific research must be conducted in this area to provide a richer understanding of emerging and reemerging disease threats. As a result, multidisciplinary approaches such as One Health will be needed to mitigate these problems.

Novel Mycobacterium tuberculosis complex isolate from a wild chimpanzee

Tuberculosis (TB) is caused by gram-positive bacteria known as the Mycobacterium tuberculosis complex (MTBC). MTBC include several human-associated lineages and several variants adapted to domestic and, more rarely, wild animal species. We report an M. tuberculosis strain isolated from a wild chimpanzee in Côte d’Ivoire that was shown by comparative genomic and phylogenomic analyses to belong to a new lineage of MTBC, closer to the human-associated lineage 6 (also known as M. africanum West Africa 2) than to the other classical animal-associated MTBC strains. These results show that the general view of the genetic diversity of MTBC is limited and support the possibility that other MTBC variants exist, particularly in wild mammals in Africa. Exploring this diversity is crucial to the understanding of the biology and evolutionary history of this widespread infectious disease.

Transmission of Mycobacterium tuberculosis between farmers and cattle in central Ethiopia

Background

Transmission of Mycobacterium tuberculosis (M. tuberculosis) complex could be possible between farmers and their cattle in Ethiopia.

Methodology/Principal Findings

A study was conducted in mixed type multi-purposes cattle raising region of Ethiopia on 287 households (146 households with case of pulmonary tuberculosis (TB) and 141 free of TB) and 287 herds consisting of 2,033 cattle belonging to these households to evaluate transmission of TB between cattle and farmers. Interview, bacteriological examinations and molecular typing were used for human subjects while comparative intradermal tuberculin (CIDT) test, post mortem and bacteriological examinations, and molecular typing were used for animal studies. Herd prevalence of CIDT reactors was 9.4% and was higher (p<0.01) in herds owned by households with TB than in herds owned by TB free households. Animal prevalence was 1.8% and also higher (p<0.01) in cattle owned by households with TB case than in those owned by TB free households. All mycobacteria (141) isolated from farmers were M. tuberculosis, while only five of the 16 isolates from cattle were members of the M. tuberculosis complex (MTC) while the remaining 11 were members of non-tuberculosis mycobacteria (NTM). Further speciation of the five MTC isolates showed that three of the isolates were M. bovis (strain SB1176), while the remaining two were M. tuberculosis strains (SIT149 and SIT53). Pathology scoring method described by “Vordermeier et al. (2002)” was applied and the average severity of pathology in two cattle infected with M. bovis, in 11 infected with NTM and two infected with M. tuberculosis were 5.5, 2.1 and 0.5, respectively.

Conclusions/Significance

The results showed that transmission of TB from farmers to cattle by the airborne route sensitizes the cows but rarely leads to TB. Similarly, low transmission of M. bovis between farmers and their cattle was found, suggesting requirement of ingestion of contaminated milk from cows with tuberculous mastitis.

Transmission of Mycobacterium tuberculosis from an Asian elephant (Elephas maximus) to a chimpanzee (Pan troglodytes) and humans in an Australian zoo

Mycobacterium tuberculosis is primarily a pathogen of humans. Infections have been reported in animal species and it is emerging as a significant disease of elephants in the care of humans. With the close association between humans and animals, transmission can occur. In November 2010, a clinically healthy Asian elephant in an Australian zoo was found to be shedding M. tuberculosis; in September 2011, a sick chimpanzee at the same zoo was diagnosed with tuberculosis caused by an indistinguishable strain of M. tuberculosis. Investigations included staff and animal screening. Four staff had tuberculin skin test conversions associated with spending at least 10 hours within the elephant enclosure; none had disease. Six chimpanzees had suspected infection. A pathway of transmission between the animals could not be confirmed. Tuberculosis in an elephant can be transmissible to people in close contact and to other animals more remotely. The mechanism for transmission from elephants requires further investigation.

Facts and dilemmas in diagnosis of tuberculosis in wildlife

Mycobacterium bovis, causing bovine tuberculosis (BTB), has been recognized as a global threat at the wildlife-livestock-human interface, a clear "One Health" issue. Several wildlife species have been identified as maintenance hosts. Spillover of infection from these species to livestock or other wildlife species may have economic and conservation implications and infection of humans causes public health concerns, especially in developing countries. Most BTB management strategies rely on BTB testing, which can be performed for a range of purposes, from disease surveillance to diagnosing individual infected animals. New diagnostic assays are being developed for selected wildlife species. This review investigates the most frequent objectives and associated requirements for testing wildlife for tuberculosis at the level of individual animals as well as small and large populations. By aligning those with the available (immunological) ante mortem diagnostic assays, the practical challenges and limitations wildlife managers and researchers are currently faced with are highlighted.

Serodiagnosis of tuberculosis in Asian elephants (Elephas maximus) in Southern India: a latent class analysis

BACKGROUND

Mycobacterium tuberculosis, a causative agent of chronic tuberculosis disease, is widespread among some animal species too. There is paucity of information on the distribution, prevalence and true disease status of tuberculosis in Asian elephants (Elephas maximus). The aim of this study was to estimate the sensitivity and specificity of serological tests to diagnose M. tuberculosis infection in captive elephants in southern India while simultaneously estimating sero-prevalence.

METHODOLOGY/PRINCIPAL FINDINGS

Health assessment of 600 elephants was carried out and their sera screened with a commercially available rapid serum test. Trunk wash culture of select rapid serum test positive animals yielded no animal positive for M. tuberculosis isolation. Under Indian field conditions where the true disease status is unknown, we used a latent class model to estimate the diagnostic characteristics of an existing (rapid serum test) and new (four in-house ELISA) tests. One hundred and seventy nine sera were randomly selected for screening in the five tests. Diagnostic sensitivities of the four ELISAs were 91.3-97.6% (95% Credible Interval (CI): 74.8-99.9) and diagnostic specificity were 89.6-98.5% (95% CI: 79.4-99.9) based on the model we assumed. We estimate that 53.6% (95% CI: 44.6-62.8) of the samples tested were free from infection with M. tuberculosis and 15.9% (97.5% CI: 9.8 - to 24.0) tested positive on all five tests.

CONCLUSIONS/SIGNIFICANCE

Our results provide evidence for high prevalence of asymptomatic M. tuberculosis infection in Asian elephants in a captive Indian setting. Further validation of these tests would be important in formulating area-specific effective surveillance and control measures.

Pinniped tuberculosis in Malayan tapirs (Tapirus indicus) and its transmission to other terrestrial mammals

In the last 7 yr, three different species of terrestrial mammals were diagnosed with Mycobacterium pinnipedii either within one collection or through the introduction of an infected animal from another zoo. The affected species included the Malayan tapir (Tapirus indicus), Bactrian camel (Camelus bactrianus bactrianus), and crested porcupine (Hystrix cristata). In the first zoo, all of these were living in exhibits adjacent to a group of South American sea lions (Otariaflavescens) and were cared for by the same keeper. One infected tapir was transferred to a different zoo and transmitted M. pinnipedii infection to three other Malayan tapirs. The tapirs were tested with various diagnostic methods, including comparative intradermal tuberculin test, PCR and culture of sputum samples, Rapid Test (RT), and multiantigen print immunoassay (MAPIA). The M. pinnipedii infection was confirmed at postmortem examination in all animals. RT and MAPIA showed the diagnostic potential for rapid antemortem detection of this important zoonotic disease.

From the mouths of monkeys: detection of Mycobacterium tuberculosis complex DNA from buccal swabs of synanthropic macaques

Although the Mycobacterium tuberculosis complex (MTBC) infects a third of all humans, little is known regarding the prevalence of mycobacterial infection in nonhuman primates (NHP). For more than a century, tuberculosis has been regarded as a serious infectious threat to NHP species. Advances in the detection of MTBC open new possibilities for investigating the effects of this poorly understood pathogen in diverse populations of NHP. Here, we report results of a cross-sectional study using well-described molecular methods to detect a nucleic acid sequence (IS6110) unique to the MTBC. Sample collection was focused on the oral cavity, the presumed route of transmission of MTBC. Buccal swabs were collected from 263 macaques representing 11 species in four Asian countries and Gibraltar. Contexts of contact with humans included free ranging, pets, performing monkeys, zoos, and monkey temples. Following DNA isolation from buccal swabs, the polymerase chain reaction (PCR) amplified IS6110 from 84 (31.9%) of the macaques. In general, prevalence of MTBC DNA was higher among NHP in countries where the World Health Organization reports higher prevalence of humans infected with MTBC. This is the first demonstration of MTBC DNA in the mouths of macaques. Further research is needed to establish the significance of this finding at both the individual and population levels. PCR of buccal samples holds promise as a method to elucidate the mycobacterial landscape among NHP, particularly macaques that thrive in areas of high human MTBC prevalence.

Development of a diagnostic gene expression assay for tuberculosis and its use under field conditions in African buffaloes (Syncerus caffer)

The development of diagnostic tests for tuberculosis (TB) in exotic species is constrained by host biology and the limited availability of suitable assay reagents. As such, we evaluated a gene expression assay (GEA) which is easily modified for novel species and allows for initial sample processing under field conditions. African buffaloes (Syncerus caffer) were categorized using the single comparative intradermal tuberculin test, and blood from test-positive and test-negative animals was incubated for 20 h in "Nil" tubes (containing saline) and "TB Antigen" tubes (containing Mycobacterium tuberculosis complex (MTC)-specific antigens) of a commercial human TB test, the QuantiFERON(®)-TB Gold (In-Tube) (QFT) assay. Blood samples were then stabilized in RNAlater(®) and transported to the laboratory for RNA extraction. A Custom TaqMan GEA was used to calculate the relative abundance of interferon-gamma (IFN-γ) mRNA in the TB Antigen tube compared to that in the Nil tube as a marker of immune activation in response to MTC antigen recognition. The GEA results from the two buffalo groups were compared and a cutoff value of 2.85 was calculated to differentiate between animals from these groups with a sensitivity of 80% (95% C.I.: 56-94%) and a specificity of 95% (95% C.I.: 75-100%). Further optimization of this assay could provide a highly useful tool for the diagnosis of MTC infection in exotic species.

Detection of Mycobacterium tuberculosis infection in dogs in a high-risk setting

Dogs infected with Mycobacterium tuberculosis can develop clinical tuberculosis (TB) but there are currently no validated immunological assays for diagnosing this infection in this species. Using a post mortem survey we investigated the prevalence of non-clinical M. tuberculosis infection and clinical TB disease in a high-risk population of dogs and developed and utilised a novel interferon-gamma release assay to determine the risk of transmission of M. tuberculosis from TB patients to contact dogs. The prevalence of clinical TB in dogs from a high-risk setting was 1% (95% CI: 0-5%) while the prevalence of immunological sensitization to M. tuberculosis antigens in dogs living in contact with sputum smear-positive TB patients was 50%. The IGRA proved a useful test of M. tuberculosis infection in dogs and the high levels of transmission of this pathogen from humans to companion dogs should be considered when assessing the zoonotic risks associated with such animals.

Detection of Mycobacterium tuberculosis infection in chacma baboons (Papio ursinus) using the QuantiFERON-TB gold (in-tube) assay

BACKGROUND

Early diagnosis of simian tuberculosis (TB) is vital to prevent transmission of this disease. We evaluated the ability of the QuantiFERON-TB Gold (In-Tube Method) assay (QFG-IT) to detect TB in chacma baboons (Papio ursinus).

METHODS

Fifty-one baboons were tested using the Tuberculin Skin Test (TST) and the QFG-IT. Baboons testing positive, and animals exposed to infected individuals, were euthanised and subjected to necropsy. Selected tissues were processed for histopathology, mycobacterial culture and genetic speciation.

RESULTS

Tuberculosis was confirmed in one TST positive/QFG-IT positive animal and one TST negative/QFG-IT positive animal. One TST positive/QFG-IT negative animal and five TST negative/QFG-IT negative animals were confirmed uninfected following necropsy.

CONCLUSION

The QFG-IT correctly detected TB in two baboons, including one TST negative individual and correctly identified six baboons as uninfected, including one TST positive individual. The QFG-IT shows promise as a sensitive, specific test for TB in chacma baboons.

Outbreak of tuberculosis caused by Mycobacterium caprae in a zoological garden

In the autumn of 2004, tuberculosis caused by Mycobacterium caprae occurred in a zoo in Slovenia. A dromedary camel (Camelus dromedarius) was killed after a history of progressive emaciation. Necropsy findings indicated disseminated tuberculosis, which was confirmed by cultivation of M. caprae. Consequently, a tuberculin skin test was performed in all epidemiologically linked animals and another dromedary camel and six bison (Bison bison) were positive and killed. Mycobacterium caprae was isolated from two bison while M. scrofulaceum and Mycobacterium spp. were found in two other bison, respectively. The second dromedary camel was found to be negative for mycobacteria under both microscopic and culture tests. The isolates were investigated with commercial identification kits, IS6110 PCR, IS6110 restriction fragment length polymorphism analysis, spoligotyping and mycobacterial interspersed repetitive units typing. Genotyping results revealed that the dromedary camel and the two bison were infected by the same M. caprae.

Transmission of Mycobacterium tuberculosis from human to cattle

We describe the first transmission of Mycobacterium tuberculosis from human to cattle confirmed by molecular typing of isolates involved in the transmission. IS6110-based restriction fragment length polymorphism analysis showed that the isolates from the cattle and farm worker who suffered from pulmonary tuberculosis 1 year prior to this case were the same strains.