Molecular Identification of Mycobacterium bovis from Post-mortem Inspected Cattle at the Abattoir and Slaughter Houses in Bauchi State, Nigeria

Abstract

Aims: Bovine tuberculosis (bTB) is a chronic infectious and contagious zoonotic disease of domestic, wild animals and humans. The disease occurs in a wide range of mammalian species and therefore, poses a public health threat. It also results in considerable economic losses in livestock production and carcass condemnation of infected cattle during meat inspection. This study was aimed at determining the prevalence of zoonotic bovine tuberculosis in slaughtered cattle, based on Post-Mortem (PM) meat inspection, Ziehl-Neelsen staining (ZN) and Polymerase Chain Reaction (PCR) techniques in abattoir and slaughter houses in Bauchi State, Nigeria. Place and Duration of study: A cross-sectional abattoir based-study was conducted on 800 slaughtered cattle in the Northern, Central and Southern Zonal abattoirs of Bauchi State, Nigeria. This work was carried out between June-September, 2013. Study Design: Experimental. Methodology: One hundred and twenty (120) tissue samples from different organs were suspected to have bTB lesions at PM 15% (120/800). Out of the samples examined 35 (29.2%) were Acid-Fast Bacilli (AFB) positive; 10 (8.3%) of which were confirmed positive for M. bovis by the confirmatory Polymerase Chain Reaction (PCR). Results: The present study found the prevalence rates of 3.33% (4/120) and 5.00% (6/120) for males and females, respectively. This gave an overall prevalence of 8.33% for bTB (M. bovis) based on PCR. Bovine TB sex-specific rates were 10.00% (4/40) and 7.50% (6/80) by PCR, in males and females respectively. Female cattle also had a higher prevalence than male cattle but there was no statistically significant association (p>0.05, x2 = 0.218) between the presence of bTB in the tissues sampled and the sex of the cattle. There was a statistically significant association (p<0.05, x2 =7.002, OR=3.363) between detection of bTB in suspected tissues and the age of cattle. Using ZN, cattle aged six (6) years and above had the highest number of positive bTB cases 67.9% (31), while cattle aged 3-5 years old had the lowest 14.81% (4/27). PCR technique, revealed age-specific prevalence rate in cattle aged 6-8 and 9-11 years were 17.07% and 5.77%, respectively. Bauchi zonal abattoir had the highest number of suspected bTB cases (62.5%), followed by Katagum (26.7%) and Misau (10.8%). Conclusion: High infection rate of bTB was found among cattle sampled in the study area, with a significant prevalence in Bauchi metropolitan abattoir than the other two (2) slaughter houses (Katagum and Misau). This showed that the prevalence of bTB was higher in Bauchi metropolitan abattoir which supplies larger population of the state with beef. These findings also demonstrated that, there is urgent need for public health authorities in the state to intervene.