Bovine tuberculosis: prevalence and diagnostic efficacy of routine meat inspection procedure in Woldiya municipality abattoir north Wollo zone, Ethiopia
2013
Aylate, Alemu | Shah, Shahid Nazir | Aleme, Haileluel | Gizaw, Tarkegn Tintagu
Bovine tuberculosis (BTB) is a widespread and endemic disease of cattle in Ethiopia posing a significant threat to public health. Regular surveillance by skin test, bacteriology, and molecular methods is not feasible due to lack of resources. Thus, routine abattoir (RA) inspection will continue to play a key role for national surveillance. A cross-sectional study was conducted at Woldiya municipal abattoir from April 1, 2009 to April 5, 2010 to estimate the prevalence of BTB in slaughtered cattle on the basis of detailed abattoir inspection and to compare efficacy of RA inspection with respect to detailed abattoir inspection and isolation and identification of Mycobacterium. Diagnostic accuracies (with corresponding measures of statistical uncertainty) were determined by computing test property statistics (sensitivity and specificity). Agreement between RA and detailed abattoir inspections was measured using kappa statistics. Out of 1,029 slaughtered heads of cattle examined during the study period, 63 (6.12 %) and 15 (1.45 %) were diagnosed with gross tuberculous lesions by detailed abattoir meat inspections and RA meat inspections, respectively, making a prevalence of 6.12 % (95 % CI: 5.2–7.1) on the basis of detailed abattoir inspection. About 59.45 % of tuberculous lesions were observed in the lungs and associated lymph nodes, whereas 35.13 % lesions were from the lymph nodes of the head. From 63 cattle suspected with tuberculosis (TB) based on detailed abattoir meat inspection, nine (19.05 %) were identified as Mycobacterium bovis, while three (4.8 %) as Mycobacterium tuberculosis. The sensitivity of RA meat inspection was 23.8 % in comparison to the detailed abattoir meat inspection and 25 % in comparison to culture, respectively. Poor agreement (k = 0.37) was seen between RA meat examination and detailed abattoir meat examination methods. Similarly, poor agreement (k = 0.013) was seen between RA meat examination and culture results. In conclusion, relatively higher prevalence (6.12 %) was recorded in Woldiya municipal abattoir on the basis of detailed Abattoir inspection and RA meat inspection protocols currently utilized in Ethiopia which are insufficient to detect the majority (76.19 %) of TB lesions at the gross level, which indicates the magnitude of meat borne zoonotic TB as an ongoing risk to public health. Detailed abattoir inspection protocols were demonstrated to improve the detection level by approximately fourfold. In conclusion, routine meat inspections have limitations in detecting BTB-suggestive lesions which indicate the magnitude of meat-borne zoonotic TB as an ongoing risk to public health.
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