Strengthening the Monitoring and Surveillance System for Bovine Tuberculosis in Post Mortem Material from Slaughtered Cattle in Eswatini: A Review

The main objective of this review study was to examine the validity of test results generated by using the Ziehl-Neelsen smear microscopy as the sole diagnostic tool for the monitoring and surveillance of bovine tuberculosis in cattle slaughtered in Eswatini.

Methods: A retrospective analysis of available laboratory data of beef carcass condemnations for a study period from 2014 to 2018 was carried out. Literature was reviewed to find out potential sample preparation and concentration methods to improve the sensitivity of current Z-N smear microscopy.

Results: The limited literature reviewed in this study has briefly highlighted (i) the limitations of using the Z-N direct smear microscopy as a screening and confirmatory laboratory test for bovine tuberculosis suspected carcasses, (ii) that the Z-N smear microscopy method may be inadequate for identifying and differentiating other acid fast bacilli co-existing in a M. bovis infection, (iii) that concentration of lymph node aspirate samples may improve the sensitivity of acid fast bacilli smear microscopy, (iv) that strategic deployment of ancillary laboratory tests, such as the Rapid diagnostic tests (RDT) and the Polymerase chain reaction test (PCR) alongside the Z-N smear microscopy may achieve an adequate level of diagnostic test performance.

Conclusion: In order to strengthen the surveillance and monitoring of bovine tuberculosis in the country, it is necessary to consider techniques for the concentration of bovine tuberculosis suspect lymph node samples, to use Rapid diagnostic test Kits in parallel to the Z-N direct smear microscopy.