BackgroundThe feeding habits and close physical contact between Ethiopian farmers and their cattle promote the transmission of tuberculosis (TB) between the farmers and their cattle. This study aimed to investigate the transmission of TB between farmers and their cattle in smallholder farms in northwestern Ethiopia.ResultsA total of 70 human TB lymphadenitis (TBLN) cases visiting the Felegehiwot Comprehensive Specialized Hospital in Bahir Dar City and 660 cattle were investigated. Half of the cattle were owned by households with TB cases, and the remaining half by TB free households. Among the 70 human TBLN patients interviewed, 65.7% (46 out of 70) of the respondents were not aware of zoonotic TB, and 67.1% (47/70) of them consumed raw milk. Positive cultures of TB were obtained in 40 of the 70 cases where TBLN tests were positive with fine needle aspiration cytology. Spoligotyping resulted in 31 different patterns, of which 25 isolates were Mycobacterium (M.) tuberculosis, and the remaining were M. africanum (4 isolates) and M. bovis (2 isolates). None of the animals showed positive test results for bovine TB by comparative intradermal tuberculin test.ConclusionsBased on the identification of M. bovis from two patients diagnosed with TBLN, we obtained preliminary evidence of zoonotic transmission of TB in northwestern Ethiopia. We did not identify a direct route of transmission between cattle and its owners. This is the objective of further investigations.

The knowledge of the diversity of strains of Mycobacterium tuberculosis complex (MTBC) species in a specific geographical region can contribute to the control of tuberculosis (TB). This study was conducted to identify the MTBC isolates to the species and spoligotype international type (SIT) level by spoligotyping. A total of 168 MTBC isolates were recovered from TB patients, spoligotyped, and their patterns were compared with those of the strains registered in the SITVIT2 database. Of 168 isolates spoligotyped, 89 patterns were identified. Ninety-eight isolates were clustered into 19 strain groups with clustering percentage of 58.3%. Forty-four strains matched the preexisting SITs in the SITVIT2 database. The dominant strains were SIT289, SIT134, and SIT3411, comprising 16.7% (28/168), 7.14% (12/168), and 4.76% (8/168) of the isolates, respectively. Euro-American (51.2%), East-African-Indian (34.5%), and M. africanum (9.52%) were the major lineages identified. Two strains of M. bovis were isolated from TB lymphadenitis cases. The high percentage of clustered strains of M. tuberculosis could suggest that a small number of lineages of M. tuberculosis are causing the disease in the area while isolation of M. bovis could suggest its zoonotic potential. Additionally, identification of M. africanum requires further confirmation by tools with a better discriminatory power.

A cross-sectional study focusing on the prevalence and assessment of the associated risk factors of bovine tuberculosis (BTB) among dairy cattle herds was conducted from 2012 to 2014 in Bahir Dar City and the surrounding districts. Comparative intradermal tuberculin test (CIDT) and interviewer administer questionnaire were used for conducting this study. Animal prevalence of BTB was 3.55% (95% confidence interval (CI): 2.26-4.84) at >=2mm cutoff value and 1.27% (95%CI: 0.49-2.05) at >=4mm cutoff value. Similarly, herd prevalence was 12.5% (95% CI: 7.78-17.2) at >=2mm cutoff value and 5.21 % (95%CI: 2.04-8.38) at >=4mm cutoff value. In a multivariable logistic regression analysis, being cross breed (adjusted OR=3 .33, 95%CI: 0.33-34.0) and having poor body condition (adjusted OR=467, 95%CI: 35.9-6086) were identified as animal level risk factors for higher tuberculin reactivity. At herd level increased risk for CIDT positivity was recorded at intensive dairy herds (adjusted OR= 10.8: 95%CI: 1.32-88.1) as compared to smallholder dairy herds. In summary, the present study revealed overall low prevalence of BTB in dairy cattle in the study area. However, comparatively higher proportion of skin reactors recorded at upgraded breeds and intensive dairy herds. This warrants the need for the designing of practically acceptable control strategy.