Prevalence of Swine Tuberculosis in Central Ethiopia and Molecular Characterization of its Causative Agents
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Date
2011-12-01
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Addis Ababa University
Abstract
A cross-sectional study was carried on 841 pigs slaughtered at Addis Ababa and Alema Swine Farm abattoirs in central Ethiopia to estimate the prevalence of swine tuberculosis (TB) and to investigate the potential risk factors associated with the prevalence as well as to isolate and characterize the causative agents. To achieve these objectives, detailed post-mortem examination, mycobacteriological culturing, molecular typing usmg multiplex polymerase chain reaction (PCR), regions of difference (RD)-4, and RD9 deletion typing, and spoligotyping were used. The prevalence of TB in the study pigs was 5.8% (49/841) on the basis of gross post-mortem lesion. The prevalence was significantly higher in older pigs than in younger pigs (10.8% versus 3.4%, X2 = 18.84; P<O.OOI). The origin of pigs was also found to significantly affect the prevalence (X2 = 27.67; P< 0.001). Pigs originated from Addis Ababa and its surrounding had prevalence of 12.8% and were more than 3 times likely to get the infection (OR=3.3, 95% CI=1.7:6.4, P<O.OOI) than pigs from Bishoftu which had a prevalence of 3.2%. In contrast, sex, floor type and water source did not significantly affect the prevalence (P>0.05). The multivariate analysis indicated that age and origin of pigs were the only statistically significant explanatory factor for variation in the recorded prevalence. Culture positivity was confirmed in 30.6% (15/49) of the pigs with TB suspected lesions. Of the 10 acid-fast positive isolates subjected to PCR 4 showed band for Mycobacterium tuberculosis complex on gel electrophoresis. Speciation of three isolates indicated that two of them were Mycobacterium tuberculosis (M tuberculosis), and one was M bovis and further strain characterization of the two M tuberculosis showed that one was SIT 53 and the other was a new strain which had not been reported to the international spoligotype database before. The findings of human type Mycobacteria probably suggest interspecies transmission pattern. SIT 53 is known to be common in human population in the country further strengthening the suggested transmission pattern given the endemic nature of TB in Ethiopia. Hence launching feasible control methods for swine TB and avoiding physical contact between infected cattle or humans and swine would be required
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Keywords
Ethiopia, Molecular typing, postmortem lesion, prevalence, risk factors, swine tuberculosis