Prevalence of Bovine Tuberculosis and Molecular Characterization of Isolates in Barka Breed Cattle in Humera, Tigray Regional State, Ethiopia
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Date
2011-06-01
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Addis Ababa University
Abstract
Bovine tuberculosis (BTB) is a chronic infectious disease of animals and humans characterized by the formation of granulomas in tissues and organs, principally caused by Mycobacterium Bovis (M bovis). A cross-sectional study was conducted from September 2010 to May 20 11 with the objectives to determine the prevalence of BTB, to characterize the isolates of Mycobacterium tuberculosis complex, and to assess zoonotic importance of BTB based on questionnaire survey in Setit and Kafta Humera districts, Western Zone of Tigray Region. Thirty one herds comprising 484 cattle were subjected to CIDT test. Accordingly, the individual animal prevalences were 6.6% (95% CI 4.4-8.8) and 8.7% (95% CI, 6.2- 11.2) at cut-offs greater than 4 mm and 2 mm, respectively while the herd prevalences were 61.3 % (95% CI, 43 .1-79.5) at cut-off >4 mm and 77.4% (95% CI, 61.8-93 .0) at cut-off >2 mm. One of the 7 milk samples collected from tuberculin-positive milking cows was culture positive. Bovine tuberculin positivity was significantly associated with body condition score(x2=13.4, P=0.001 at cut-off >4 mm; x2=6.8 P=0.033 at cut-off >2 mm), while the other assessed potential risk factors were not statistically significant. Thus, animals with medium body condition score (OR=5.5 [95% cr, 1.9-15.9] at cut-off >4 mm; OR=2.7 [95% CI, 1.2-5 .8] at cut-off >2 mm) had a higher odds for tuberculin reactivity. On abattoir survey, a total of 582 cattle were subjected to postmortem examination, of which 5.8% were found to be positive for gross tuberculous lesions Larger proportion (61. 8%) of TB suggestive lesion was recorded in the respiratory pathway followed by digestive system and prescapular lymph nodes with 23 .5% for each. Among the risk factors assessed in abattoir survey, age (x2=6.8, P=0.009) and body condition (X2=74.5, P=0.000) were significanly associated with the presence of TB suggestive lesion. Thus, animals older than 6 years (OR=3.7 [95% CI, 1.3-10.7]) and with poor body condition score (OR=53.4 [95% CI, 7.1-402.4]) had a higher odds for tuberculin reactivity. Of 34 tissue specimens collected from the gross lesions 35.3% (12/34) were positive on primary culture, of which four showed a positive signal for the genus Mycobacterium using multiplex PCR and none of them were in Mycobacterium luberculusis complex. The result suggests the importance of non-tuberculosis mycobacteria in cattle of the study area and recommended further study to reveal the specific species of mycobacteria and their public health significance in human
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Keywords
Bovine tuberculosis, cattle, Humera, Mycobacterium tuberculosis complex