Identification and genotyping of Mycobacterium tuberculosis complex infections at the human/domestic animals/wildlife interface in Nigeria and South Africa

The relevance of the use of molecular tools in the global epidemiology of Mycobacterium tuberculosis complex (MTBC) cannot be undermined. Molecular epidemiological studies of the MTBC in Nigeria are not extensive, and to date, there has only been one detailed report. More strains are therefore needed to be genotyped in order to give a clear indication of disease transmission chains and to highlight routes of infection particularly with respect to zoonotic tuberculosis. This study therefore focuses on the identification and genotyping of MTBC isolates in south western Nigeria, with emphasis on interactions occurring at the human/livestock interface. The molecular epidemiology of M. bovis strains in Hluhluwe-iMfolozi Park in South Africa was also undertaken. Prior to this study, a pilot study was initially done to establish techniques, using samples from Belgium. Mycobacterium bovis strains were first identified in Belgium using the Multiple locus [variable number of tandem repeats] (MLVA) technique and analysis was done using capillary electrophoresis. In this study, the Belgium isolates were repeated using MLVA and analysis by agaorse gel electrophoresis and the two analysis techniques compared. Human isolates (136) and livestock isolates from cattle (50), pigs (12) and goats (5) isolated in Nigeria were also used and species identification of the members of the MTBC were done using the deletion analysis PCR technique amplifying RD1mic, RD2seal, RD4 andRD9 regions as well as spoligotyping. Seventy four positive MTBC strains (humans and livestock) were genotyped using 16 VNTR loci. The discriminatory ability of the 16 loci MLVA was compared with spoligotype data on 33 MTBC strains. Mycobacterium bovis isolates from buffalo in HluhluweiMfolozi Park (HiP) South Africa, were also genotyped using the 16 loci MLVA and spoligotyping. Results indicated that agarose based MLVA is as discriminatory as the capillary based MLVA. Furthermore, the relevance of molecular techniques in the rapid identification and genotyping of members of the MTBC, especially in a tuberculosis endemic setting like Nigeria, is also highlighted. This was clearly seen in the identification of undescribed spoligopatterns of the LAM 10-CAM M. tuberculosis strains in humans as well as the identification of undescribed M. bovis spoligopatterns in livestock isolates. The prevalent M. bovis strain (SB0944) in Nigeria was also identified in a human isolate. Also, two classical M. bovis strains were identified in two human isolates obtained from cattle traders, thus suggesting the influence of close interaction between infected animals and man as a means of zoonotic tuberculosis transmission. Mycobacterium tuberculosis was also identified in three isolates, from cattle, pig and goat; with the goat isolate having a spoligopattern (EAI5) typical of strains indigenous to East Africa and India. This study demonstrated the prevalent strains of M. bovis and M. tuberculosis circulating in Nigeria with SB0944 the predominant M. bovis spoligotype and LAM10-CAM the predominant M. tuberculosis spoligotype. The MLVA results revealed the occurrence of interspecies transmission of mycobacterial species, which was seen as isolates from different animal species having identical VNTR profiles and thus belonging to the same genotype. In the HiP, two strains of M. bovis were identified, a strain previously described in cattle and buffalo in other regions of South Africa and a new undescribed strain, thus giving an indication of the circulating strains in HiP and also suggesting possible sources of introduction of novel species in HiP. The relevance of a detailed molecular epidemiological study was clearly demonstrated in both Nigeria and HiP. Strain relatedness and interactions occurring at human/livestock interface and domestic/wild life interface could also clearly be demonstrated.Dissertation (MSc)--University of Pretoria, 2008.Veterinary Tropical Diseasesunrestricte

Original Mycobacterial Sin, a consequence of highly homologous antigens?

The role of antigens shared between Mycobacteria in in-vivo cross-reactive immune responses in host animals, have been reported to be responsible for reduced BCG vaccination efficacy as well reduced specificity of routine immunological diagnostic tests. This presents with significant disease control challenges in humans and animals. The present review highlights the results of previous studies on the effect of pre-sensitization to environmental mycobacteria on either pathogenic mycobacteria and/or M. bovis BCG, in experimental animals. It also takes an in-depth view into assessing the genetic similarities and relationships between atypical mycobacteria and Mycobacterium tuberculosis complex (MTBC) and how they might explain the immunological imprint of environmental mycobacteria in directing the hosts’ immune response upon subsequent exposure to other classes of mycobacteria. The outcome of this review suggests that genetic closeness between particular atypical mycobacteria and MTBC usually indicate a higher level of homology for certain shared protective antigens. This ultimately results in a higher level of cross reactive immune responses as compared with other atypical mycobacteria that are further away genetically. This would explain the different effects of environmental mycobacteria on MTBC that have been reported in the different studies. In other words the direction of the host immune system in response to exposure to MTBC would depend on the type of environmental mycobacteria that was encountered in the initial exposure. We also explain these mycobacterial interactions in the context of the phenomenon of “Original Mycobacterial Sin”. The effects of these inevitable mycobacterial interactions on field diagnosis and control by vaccination and how to circumvent them are discussed.http://www.elsevier.com/locate/vetmicam2017Veterinary Tropical Disease

The first report of Escherichia fergusonii isolated from non-human primates, in Africa

The aim of this study was to determine the resistance phenotypes of selected enteric bacteria isolated from nonhuman primates at a wildlife-human interface. Bacterial isolates from faecal samples of non-human primates at two wildlife rehabilitation centres in South Africa were screened for the presence of Escherichia coli. The biochemical characterisation of E. coli and E. coli-like bacteria revealed both adonitol positive and sorbitol negative strains – a unique characteristic of Escherichia fergusonii and Escherichia coli K99. Further tests were carried out to identify the isolates, namely growth on Simmons citrate agar supplemented with 2% adonitol and biochemical tests based on their ability to ferment cellobiose and D-arabitol. Antimicrobial sensitivity was determined with microbroth dilution tests employing microtitre plates with 21 different antimicrobial drugs. Molecular characterisation was done with a duplex polymerase chain reaction (PCR) assay that targeted the yliE and EFER_1569 genes. E. fergusonii strains were confirmed by the presence of a 233 bp segment of the yliE gene and a 432 bp segment of the EFER_1569 gene. Twenty-three E. coli-like bacteria were confirmed as E. fergusonii based on the confirmatory tests and they were in 100% agreement. Approximately 87% of them were resistant to polymyxins B and E (colistin) as well as the carbapenem group with occasional resistance to amikacin. This is the first reported isolation and identification of E. fergusonii strains in non-human primates. The findings point to E. fergusonii as a possible emerging pathogen of zoonotic importance.https://www.elsevier.com/locate/onehltam2018Veterinary Tropical Disease

The contribution of veterinary medicine to public health and poverty reduction in developing countries

Few studies have explicitly examined the linkages between human health, animal disease control and poverty alleviation. This paper reviews the contribution that veterinary medicine can make to poverty alleviation in sub-Saharan Africa. Our analysis attempts to explore aspects of this contribution under five themes: food production; food safety; impact and control of zoonotic infections; promotion of ecotourism; and environmental protection. While these areas of human activity have, more or less, fallen under the influence of the veterinary profession to varying degrees, we attempt to unify this mandate using a ‘One Health’ narrative, for the purpose of providing clarity on the linkages between the veterinary and other professions, livestock production and poverty alleviation. Future opportunities for improving health and reducing poverty in the context of developing African countries are also discussed. We conclude that veterinary science is uniquely positioned to play a key role in both poverty reduction and the promotion of health, a role that can be enhanced through the reorientation of the profession’s goals and the creation of synergies with allied and related professions.Le relazioni tra salute umana, controllo delle patologie animali e programmi di riduzione della povertà raramente sono state oggetto di analisi. Questo articolo analizza il contributo che la medicina veterinaria può fornire ai processi di riduzione della povertà nell’Africa sub‑sahariana. In particolare, vengono analizzate le implicazioni della medicina veterinaria su: produzione di alimenti, igiene alimentare, impatto e controllo delle zoonosi, promozione di ecoturismo e protezione dell’ambiente. Lo studio ha l’obiettivo di riconsiderare questi aspetti sulla base dell’approccio “One Health” e di chiarire le relazioni che la professione veterinaria ha con le altre professioni, gli allevamenti animali e i programmi di riduzione della povertà. L’articolo esamina le opportunità future per migliorare le condizioni di salute e ridurre il sottosviluppo nei paesi africani, evidenziando il ruolo determinante delle scienze veterinarie. Ruolo che può essere ancor più potenziato attraverso la ridefinizione degli obiettivi professionali e la creazione di sinergie con le altre professioni.http://www.izs.it/vet_italiana/issues_vet_it.htmhb201

Field application of immunoassays for the detection of Mycobacterium bovis infection in the African buffalo (Syncerus caffer)

The African buffalo (Syncerus caffer) is considered the most important maintenance host of bovine tuberculosis (BTB) in wildlife in Southern Africa. The diagnosis of Mycobacterium bovis infection in this species mostly relies on the single intradermal comparative tuberculin test (SICTT). As an alternative, the BOVIGAM®1G, an interferon-gamma (IFN- ) release assay, is frequently used. The test performance of cell-mediated immunity (CMI-) and humoral immunity (HI-) based assays for the detection of M. bovis infections in buffaloes was compared to identify the test or test combination that provided the highest sensitivity in the study. Buffaloes were sampled during the annual BTB SICTT testing in the Hluhluwe-iMfolozi-Park (KwaZulu-Natal, South Africa) during June 2013. A total of 35 animals were subjected to the SICTT, 13 of these tested positive and one showed an inconclusive reaction. CMI-based assays (BOVIGAM®1G (B1G) and BOVIGAM®2G (B2G)) as well as a serological assay (IDEXX TB ELISA) were used to further investigate and compare immune responsiveness. Thirteen SICTT positive buffaloes and one inconclusive reactor were slaughtered and a post-mortem (PM) examination was conducted to confirm BTB. Lesions characteristic of BTB were found in 8/14 animals (57.1%). Test results of individual assays were compared with serial and parallel test interpretation and the sensitivity was calculated as a percentage of test positives out of the number of SICTT positive animals with granulomatous lesions (relative sensitivity). The B1G assay showed the highest individual sensitivity (100%; 8/8) followed by the B2G assay (75%; 6/8) and the IDEXX TB ELISA (37.5%; 3/8). Therefore, using in parallel interpretation, any combination with the B1G showed a sensitivity of 100% (8/8), whereas combinations with the B2G showed a 75% sensitivity (6/8).Out of the 21 SICTT negative animals, 7 animals showed responsiveness in the B2G or IDEXX TB ELISA. In conclusion, this study has shown that the BOVIGAM®IFN- assay had the highest test performance.WOTRO Science for Global Development (grant W01.65.321.00).http://www.elsevier.com/locate/vetimmhb2016Veterinary Tropical Disease

Mycobacterium tuberculosis and Mycobacterium africanum in stools from children attending an immunization clinic in Ibadan, Nigeria

BACKGROUD: Tuberculosis is a major cause of chilhood morbidity and mortality in Nigeria. Diagnosis of childhood tuberculosis is a global challenge making early treatment a mirage. In this study we investigated the stools of children for the presence of mycobacteria. METHODS: Stool samples from children aged 3 days to 3 years who presented for postnatal immunization at a large University-based clinic in Nigeria, were subjected to Ziehl-Neelsen staining. Samples with acid-fast bacilli wer further processed using mycobacterial culture, spoligotyping, and deletion typing. RESULTS: One hundred and ninety-two stool samples from different children were collected and processed. Thirty (15.6%) had acid-fast bacilli. Of these, eight had Mycobacterial tuberculosis and one had Mycobacterial africanum. CONCLUSION: Approximetely 5% (9/192) of apparently well children had evidence of potentially serious tuberculosis infection. The usefullness of stool specimens for diagnosing pediatric tuberculosis warrants further investigation

Cross reactive immune responses in cattle arising from exposure to Mycobacterium bovis and non-tuberculous mycobacteria

Accurate diagnosis of tuberculosis in cattle may be compromised in areas where there are high rates of exposure to environmental/non-tuberculous mycobacteria (NTM). This cross reaction of immune responses to Mycobacterium bovis antigens shared with NTMs can result in reduced specificity of commonly used diagnostic tests including tuberculin skin tests and the interferon gamma assay (IFN-ɣ). In this study we assessed the cross-reactive immune responses of M. bovis (infected) and NTM exposed animals to M. bovis and M. avium tuberculin, the ESAT6/CFP10 cocktail antigen, tuberculin derived from cultures of selected NTMs, and a panel of recombinant mycobacterium tuberculosis complex (MTBC) antigens sharing homology with orthologues in NTM. Gamma interferon (IFN-ɣ) responses were measured in whole blood cultures using the IFN-ɣ assay and the IFN-ɣ elispot assay on purified peripheral blood mononuclear cells (PBMC). We observed the expected strong IFN-ɣ response to PPD-B in the M. bovis infected animals that distinguished this group from non-infected NTM exposed cattle. The IFN-ɣ responses to PPD-N (M. nonchromogenicum), were relatively high in both infected and non-infected NTM exposed cattle, but were not significantly different to classify the true infection status of each group. The results indicated that the cross-reactive responses to PPD-B and/or PPD-A with PPD-N, likely arose from prior exposure to environmental non-tuberculous mycobacteria. The IFN-ɣ immune responses to the 10 R-Mag measured by the IFN-ɣ elispot assay revealed that three of the selected antigens, Rv3615 (ESpC), Rv0287 (esxG) and the ESAT6/CFP10, were immunogenic in the infected cattle, and distinguished the infected cattle from the non-infected NTM exposed animals. The combined data of PPDs and R-Mags derived from NTM mycobacteria may prove useful in future development of novel bTB diagnostic tests.http://www.elsevier.com/locate/prevetmed2019-04-01hj2019Production Animal StudiesVeterinary Tropical Disease