Conventional and Molecular Epidemiology of Bovine Tuberculosis in Dairy Farms in Addis Ababa City, the Capital of Ethiopia

A cross-sectional investigation of Bovine Tuberculosis (BTB) was conducted on 1132 dairy cattle from 56 herds using comparative intradermal tuberculin test (CIDT), postmor¬tem examination, bacteriological culturing, and molecular typing of mycobacterium isolates involving spoligotyping and variable number of tandem repeat (VNTR). Herd and individual BTB prevalence rate was found to be 53.6% (95% CI=39.74- 67.00) and 34.1% (95% CI =31.33-36.92) respec¬tively. The individual animal prevalence was significantly affected by both herd size (x2 = 10.9, p<0.001) and age of the animals (x2= 56.4, p<0.001). Moreover, a strong positive correlation (r=0.89, p<0.001) was observed between herd size and number of reactor animals. However, there was no statistically significant association (P>0.05) between reactor herd and years of establishment of the farm, origin and status of the animal. Typical tuberculous lesions were detected on 72.7% (8/11) of sacrificed tuberculin reactors animals and mycobacterial isolates were recovered by culturing from 100% (11/11) of tissue specimens. Among these, eight isolates were M. bovis while three were M. tuberculosis. All M. bovis isolates were further classified into three different spoligotyping patterns and two different VNTR profiles. In conclusion, the result of the present study showed high prevalence of BTB in Addis Ababa City dairy farms, and the identification of three M. bovis spoli- gotype pattern from eleven animals only merely suggests a possible presence of more strains in the region.