Exploring the use of molecular epidemiology to track bovine tuberculosis in Nigeria: An overview from 2002 to 2004

Systematic review and meta-analysis of tuberculosis in animals in Nigeria

Animal tuberculosis (TB) is a contagious and chronic disease caused by mycobacteria belonging to theMycobacterium tuberculosis complex (MTBC) in domestic and wild animals. MTBC strains infection has been confirmed in many animal species in Nigeria, including captive wildlife, cattle, dromedary camels, goats, and pigs. Despite widespread infection and the potential impact of the disease on public health, active surveillance and control strategies are absent in Nigeria. This study aimed to conduct the first comprehensive meta-analysis to assess the distribution of tuberculosis and analyze the potential moderators of infection in animals in Nigeria. Eligible studies (sixty-one (Cadmus et al., 2014) [61] prevalence and seven (Menzies and Neill, 2000) [7] case reports) were retrieved and included in the analysis. The analyses showed an overall pooled TB prevalence of 7.0% (95% CI: 6.0-8.0) comprising of infection distributed in cattle (8.0%, 95% CI: 7.0-8.0), goats (0.47%, 95% CI: 0-1.2), sheep (0.27%, 95% CI: 0.14-0.46), camels (13.0%, 95% CI: 0-47), and wildlife (13.0%, 95% CI: 9-16) respectively. The occurrence of infection was significantly moderated by the publication periods, geographical location, sample size, and detection methods. TB prevalence was heterogeneous across several predictors, with the year of publication exhibiting a higher rate (46%) of the detected heterogeneity. These findings should provide policy-relevant information to guide the design and establishment of prevention and control measures amenable to the local situations in Nigeria.

Prevalence and molecular characterization of Mycobacterium tuberculosis complex in cattle and humans, Maiduguri, Borno state, Nigeria: a cross-sectional study

INTRODUCTION

Globally, the highest burden of bovine and human tuberculosis resides in Africa and Asia. Tuberculosis (TB) is the second leading single infectious killer after severe acute respiratory syndrome corona virus-2 (SARSCOV-2). Bovine TB remains a treat to wild and domesticated animals, humans and hinders international trade in endemic countries like Nigeria. We aimed at determining the prevalence of bovine and human tuberculosis, and the spoligotypes of Mycobacterium tuberculosis complex in cattle and humans in Maiduguri.

METHODS

We conducted a cross sectional study on bovine and human tuberculosis in Maiduguri, Borno state. We calculated sample size using the method of Thrusfield. Lesions suggestive of TB from 160 slaughtered cattle were obtained from Maiduguri Central Abattoir. Sputum samples from humans; 82 abattoir workers and 147 suspected TB patients from hospitals/clinics were obtained. Lesions and sputum samples were cultured for the isolation of Mycobacterium spp. Positive cultures were subjected genus typing, deletion analysis and selected isolates were spoligotyped. Data was analysed using SPSS VERSION 16.0.

RESULTS

Prevalence of 32.5% (52/160) was obtained in cattle. Damboa local government area (LGA), where majority of the infected animals were obtained from had 35.5% bTB prevalence. All categories analysed (breed, age, sex, body conformation and score) had P-values that were not significant (P > 0.05). Sputum culture revealed a prevalence of 3.7% (3/82) from abattoir workers and 12.2% from hospitals/clinics. A significant P-value (0.03) was obtained when positive culture from abattoir and that of hospitals/clinics were compared. Out of the 52 culture positive isolates obtained from cattle, 26 (50%) belonged to M. tuberculosis complex (MTC) and 17/26 (65.4%) were characterized as M. bovis. In humans, 7/12 (58.3%) MTC obtained were characterized as M. tuberculosis. Spoligotyping revealed SB0944 and SB1025 in cattle, while SIT838, SIT61 of LAM10_CAM and SIT1054, SIT46 of Haarlem (H) families were obtained from humans.

CONCLUSIONS

Cattle in Damboa LGA need to be screened for bTB as majority of the infected animals were brought from there. Our findings revealed the presence of SB0944 and SB1025 spoligotypes from cattle in Borno state. We isolated M. tuberculosis strain of the H family mainly domiciled in Europe from humans.

Prevalence of bovine tuberculosis in slaughtered cattle and factors associated with risk of disease transmission among cattle handlers at Oko-Oba Abattoir, Lagos, Nigeria

Background and Aim:

Bovine tuberculosis (bTB) is a zoonotic disease of major public health importance, especially in many developing countries, including Nigeria, where control measures are largely not applied, and the risks of human infection are high. This study was aimed at determining the current prevalence of bTB in slaughtered cattle and identifying factors associated with the risk of disease transmission among cattle handlers toward making informed control measures to limit human-animal interface disease transmission.

Materials and Methods:

Serum samples at slaughter and lesions suggestive of bTB collected during postmortem examination of 187 slaughtered cattle at the Oko–Oba Abattoir, Agege, Lagos State, Nigeria, were subjected to lateral flow and Ziehl–Neelsen (ZN) techniques, respectively. Furthermore, a structured questionnaire was interviewer-administered to 156 cattle handlers to investigate associated exposure factors to bTB infection. Data were analyzed using bivariate and multivariate logistic regression.

Results:

The prevalence of bTB in cattle was 25.7% and 7.0% by lateral flow technique and ZN, respectively. The seropositivity was highest in cattle with poor body condition (50.0%), then with good (36.4%) and fair (25.0%) body conditions. The questionnaire survey revealed that being in livestock handling business for >6 years (p=0.001), not knowing the mode of transmission (p=0.02) and ignoring TB lesions at slaughter (p=0.02) were exposure factors associated with increased risk of bTB infection among the cattle handlers. Further, multivariate analysis showed that those who spent more than 6 years in livestock handling were about 4 times (Adjusted odds ratio [AOR]=3.5; 95% confidence interval [CI]=1.1-7.6, p=0.01) more likely to be exposed to bTB infection than those with lesser years. Again, respondents who called the attention of meat inspectors on seeing lesions in animals were about 4 times less likely to be exposed to bTB infection than those who ignored it (AOR=0.3; CI=0.1-0.8, p=0.01).

Conclusion:

This study has reiterated the endemicity of bTB in cattle population in Nigeria, with the prevalence of 25.7% and 7.0% of bTB by lateral flow and ZN techniques, respectively. This portends potential risk for disease transmission at the human-animal interface, particularly at the abattoir setting. The study also identified important knowledge and practice gaps which would enable informed, all-inclusive, and well-directed programs for effective control of the disease in both human and cattle populations.

Bovine tuberculosis: within-herd transmission models to support and direct the decision-making process

Use of mathematical models to study the transmission dynamics of infectious diseases is becoming increasingly common in veterinary sciences. However, modeling chronic infectious diseases such as bovine tuberculosis (bTB) is particularly challenging due to the substantial uncertainty associated with the epidemiology of the disease. Here, the methodological approaches used to model bTB and published in the peer-reviewed literature in the last decades were reviewed with a focus on the impact that the models' assumptions may have had on their results, such as the assumption of density vs. frequency-dependent transmission, the existence of non-infectious and non-detectable stages, and the effect of extrinsic sources of infection (usually associated with wildlife reservoirs). Although all studies suggested a relatively low rate of within-herd transmission of bTB when test-and-cull programs are in place, differences in the estimated length of the infection stages, sensitivity and specificity of the tests used and probable type of transmission (density or frequency dependent) were observed. Additional improvements, such as exploring the usefulness of contact-networks instead of assuming homogeneous mixing of animals, may help to build better models that can help to design, evaluate and monitor control and eradication strategies against bTB.

Experimental aerosol Mycobacterium bovis model of infection in goats

The use of animal models is essential in testing the efficacy for novel therapies against tuberculosis (TB). Calves and non-human primates are examples of large animal models currently used to test TB vaccine efficacy but these animals are difficult and very expensive to house under high containment conditions. The goat may represent an effective but less expensive alternative for testing prototype vaccines against TB. Goats are susceptible to Mycobacterium bovis, Mycobacterium caprae and Mycobacterium tuberculosis infection. Aerosolized bacteria are the most common source of natural infection in humans and the primary site of natural infection is the respiratory tract. We developed a simple procedure for infecting goats with M. bovis by aerosol exposure. After 8 and 12 weeks of infection the goats were euthanized, post-mortem analysis was performed, and all exposed animals presented TB compatible lesions in the lung and associated lymph nodes. Selected lung lesions and respiratory lymph nodes were evaluated and cultured for bacteriological and histological analysis. The present work shows a reliable new animal model of aerosol infection to be used in the understanding of TB disease and development of new therapies.

Naming spoligotype patterns for the RD9-deleted lineage of the Mycobacterium tuberculosis complex; www.Mbovis.org

This www.Mbovis.org website and associated databases were initiated in response to the need of the Mycobacterium bovis molecular typing community for standardisation of nomenclature for spoligotype patterns. The purpose of the website is to provide standardised names for spoligotype patterns from strains of the RD9-deleted, lineage of the Mycobacterium tuberculosis complex. Each unique spoligotype pattern is named by 'SB' followed by a four integer number (e.g. SB0120) and the database currently records over 1400 patterns submitted by the research community over the last 9 years. The database holds information and authoritative names for spoligotype patterns from both clades of Mycobacterium africanum, M. bovis (antelope), Mycobacterium microti, Mycobacterium pinnipedii, Mycobacterium caprae and M. bovis. The history of the database is described, as well as the method for submitting new patterns to the database and the functionality of the website.