Prevalence and associated risk factors of brucellosis in sheep and goat from South Omo Zone, Ethiopia

Brucellosis is known as a highly contagious zoonotic bacterial disease, with a significant effect on the livestock industry. It is caused by several species of cocco-bacilli Gram-negative bacteria from the Genus Brucella, and distributed worldwide including Ethiopia. However, there was a scarcity of epidemiological data on its occurrence in pastoral areas. A cross-sectional investigation was performed from September 2018 to June 2019, to estimate the seroprevalence of brucellosis and to characterized main Brucella isolates infecting small ruminants in two randomly selected pastoral districts of the South Omo Zone, Ethiopia. A pre-tested questionnaire was used and collected data were subjected to statistical analyses (multivariate logistic regression). For the serological test, blood samples were drawn from a total of 124 small ruminants with a history of abortion. Subsequently, 30 vaginal swabs were sampled from seropositive animals for Brucella isolation. All sera were first analyzed serologically bya modified Rose Bengal Plate Test (mRBPT) and Brucellaseropositivity was further confirmed by Complement Fixation Test (CFT). The brucellosis seroprevalence among small ruminants with a history of abortion was 21% (26/124; 95% CI: 0.14 - 0.28). Multivariable logistic regression analysis showed that the main risk factors related to Brucella spp. infections were history of abortion (OR: 0.28, 95% CI: 0.18 - 0.43) and parity numbers (OR: 0.20, 95% CI: 0.059 - 0.72). Brucella spp. were also isolated from 5 (16.7%) of the 30 vaginal swabs cultured on Brucella Selective Agar.  The isolates were identified as B. melitensis based on biochemical and bacteriological culture results. In conclusion, this study revealedthehigh prelance of brucellosis in small ruminants in the studied area. Therefore, regular testing of breeding animals is necessary to reduce brucellosis and its economic impact in the region.