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BACKGROUND: Bovine tuberculosis (bTB) is a zoonotic disease with great economic impact estimated at billions of dollars annually worldwide. Meat inspection represents a long-standing form of disease surveillance that serves both food safety and animal health. The objective of this study was to determine the prevalence of bTB in livestock at abattoirs using a cell-mediated immune (CMI) assay, the gamma interferon (IFN-I³) assay. This cross-sectional study was conducted at selected abattoirs (low-throughput, high-throughput and rural/informal) in Gauteng province, where animals were also subjected to routine meat inspection. RESULTS: A total of 410 fresh blood samples were collected from slaughter livestock (369 cattle and 41 sheep) from 15 abattoirs, and analysed using Bovigam® test kit with bovine, avian and Fortuitum purified protein derivatives (PPD) as blood stimulating antigens. The estimated prevalence of bTB in cattle was 4.4% (95% CI: 2.4%-7.3%). The prevalence of bTB in cattle varied between abattoirs (p = .005), ranging from 0% to 23%; however, there were no significant differences among genders, breeds, municipality, districts, origins of animals (feedlot, auction or farm) or throughput of abattoirs. The prevalence of avian reactors was 6.0% (95% CI: 3.6%-9.2%) in cattle, varying between abattoirs (p = .004) and ranging from 0% to 20.7%. None of the sheep with valid test results was positive for bTB and none was avian reactors (95% CI: 0%-15%). CONCLUSION: The detection of bTB reactor cattle in our study clearly shows the limitation of disease surveillance using a meat inspection approach, as all the 410 slaughter animals sampled had passed visual abattoir inspection and been classified as bTB-free. Our findings therefore emphasize the risk of zoonotic transmission of bTB to abattoir workers and potential food safety hazard to consumers. Furthermore, our study highlights the potential for the use of the IFN-I³ assay to reduce this risk.

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains an ongoing threat to human health. Many plant species contain antimycobacterial compounds, which may serve as template molecules for new anti-TB drugs. The Rubiaceae family is the largest family of trees in southern Africa, and preliminary evidence revealed antimycobacterial activity in several species of the genus, motivating further studies. Leaf extracts of 15 tree species from the Rubiaceae family were screened for antimycobacterial activity against pathogenic M. tuberculosis and non-pathogenic Mycobacterium smegmatis, Mycobacterium aurum and Mycobacterium bovis BCG (Bacillus Calmette-Guérin) using a twofold serial microdilution assay. Cytotoxicity was determined using a tetrazolium-based colorimetric assay against C3A liver cells and Vero kidney cells. Minimum inhibitory concentration values as low as 0.04 mg/mL against M. smegmatis and M. tuberculosis were recorded. Activity against M. aurum was the best predictor of activity against pathogenic M. tuberculosis (correlation coefficient = 0.9). Bioautography indicated at least 40 different antimycobacterial compounds in the extracts. Cytotoxicity of the extracts varied, and Oxyanthus speciosus had the most promising selectivity index values.

Bovine tuberculosis (BTB), a chronic disease of mammals caused by Mycobacterium bovis, is a threat to South African wildlife. It has been reported that African buffaloes (Syncerus caffer) are reservoir hosts of BTB in South African wildlife populations. This study reports on the molecular identification and typing of 31 M. bovis isolates collected between 1993 and 2008, mainly from buffaloes but also from two lions and a bush pig, in the Hluhluwe-iMfolozi Park (HiP) in KwaZulu-Natal. To study the dynamics of BTB in the buffalo populations, 28 M. bovis isolates from the HiP and epidemiologically related parks were characterised using regions of difference deletion analysis for species identification and spoligotyping, variable number of tandem repeats (VNTR), polymorphic G-C-rich sequences and IS6110 restriction fragment length polymorphism (RFLP) genotyping methods. At least three distinct M. bovis genotypes were found amongst HiP samples. The combination of VNTR typing (using a 16-loci panel) and IS6110 RFLP revealed the presence of three additional genetic profiles in individual buffaloes, demonstrating that the highest level of discrimination was achieved by these typing methods. One of the observed spoligotypes (SB0130) was dominant and represented 75% of isolates from buffaloes. A novel M. bovis spoligotype (SB1474), which is reported for the first time in this study, was observed in 14.3% of isolates from buffaloes. Based on the observed genetic relationships, the findings suggest independent introductions from at least three unrelated sources. These findings improve the knowledge regarding the diversity of circulating M. bovis strains in the HiP.