Role of abattoir monitoring in determining the prevalence of bovine tuberculosis: a systematic review and meta-analysis.
Bovine tuberculosis (bTB) is one of the major zoonotic concerns of the world, as milk and meat from cattle are major products for human consumption. Bovine tuberculosis not only affects the health of cattle and poses an imminent zoonotic threat, but also causes significant economic loss in both developed and developing countries. This systematic review reports the prevalence of Mycobacterium tuberculosis complex (MTBC) organisms in slaughtered cattle showing tuberculosis-like lesion (TBL) with available literature worldwide. Appropriate keywords were used to search various databases to collect articles pertaining to slaughterhouse studies. Bovine TB prevalence, based on the prevalence of MTBC organisms in slaughtered cattle showing TBL by culture, microscopy, PCR and spoligotyping, was assessed in each study using a random-effects model and standardized mean with 95% confidence interval (CI). Heterogeneity was assessed by the I2 statistic. Publication bias was evaluated using funnel plots. Out of 72 hits, 37 studies were selected based on title and abstract. Ten articles were excluded due to lack of desired data, and 27 studies were included in the final analysis. From the selected articles, it was found that 426 [95% CI: 302-560] per 1,000 slaughtered cattle with TBL were positive for the presence of MTBC organisms. The sensitivity analysis showed that no individual study alone influenced the estimation of pooled prevalence. The prevalence of MTBC organisms in slaughtered cattle showing TBL by culture, microscopy, PCR and spoligotyping was 474[95% CI: 342-610], 385 [95% CI: 269-515], 218 [95% CI: 132-338], 326 [95% CI: 229-442], respectively, per 1,000 slaughtered cattle. Most of the slaughtered cattle were from the same locality as the slaughterhouse. The results obtained in this study suggest that abattoir monitoring can give an estimate of the prevalence of bTB in that locality. This study also emphasizes the need to test cattle and animal handlers who were in contact with bTB-positive cattle.