Sero-prevalence and risk factors associated with brucellosis in ruminants and humans in selected districts of West Shoa zone, Oromia regional state, Ethiopia

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Addis Ababa University


A cross-sectional seroprevalence study was conducted in Bako Tibe, Ilu Galan, and Nono districts of the West Shoa zone, from January - May 2021 to estimate the seroprevalence and identify associated risk factors of brucellosis in ruminants and humans, as well as to assess the knowledge and practices of livestock owners towards the disease. A total of 295 blood samples were collected for serological tests from ruminants using a simple random sampling, whereas the districts and kebeles were selected purposively. In addition, 102 human sera were included in the study. Rose Bengal Plate test was used to screen the serum samples, and indirect enzyme-linked immunosorbent assay was employed as a confirming test. Besides, information was collected on the individual animal and herd-level risk factors using a structured questionnaire. Descriptive statistics were used to summarize the prevalence of brucellosis and present the questionnaire survey results. Firth's bias-reduced logistic regression was used to determine the association between the prevalence of brucellosis and the risk factors. The overall seroprevalence of brucellosis was 3.3 % (95 % CI: 1.73-6.34) by Rose Bengal Plate test and 1.3 % (95 % CI: 0.43 -3.67) by indirect enzyme-linked immunosorbent test, of these,1.17% (95 % CI: 0.14 - 4.18) in cattle, 1.63% (95 % CI: 0.04 - 8.7) in sheep and 1.56% (95 % CI: 0.03 - 8.4) in goats. The result of univariable firth's bias-reduced logistic regression analysis indicates that animals with the history of abortion (OR= 26, P= 0.003), species composition (OR= 8, P= 0.023), and retained fetal membrane (OR=9, P=0.034) were found significantly associated with brucellosis. Nevertheless, in the multivariable firth's bias-reduced logistic regression analysis, history of abortion (OR=10.72, 95 % CI: 1.06 -131.26, P = 0.044) and species composition (OR=12.37, 95 % CI:0.98 -155.67, P = 0.03) were statistically significant risk factors of ruminant brucellosis. Four blood clots from seropositive animals were further tested with real-time PCR and the result revealed that all samples were negative for IS711 primers. Similarly, no human sera were found positive for Brucella antibodies. A total of 120 peoples were questioned to evaluate their awareness and practices regarding to brucellosis. Accordingly, most respondents 71.7% did not know brucellosis and 50% of them practices handling animals’ delivery. In conclusion, despite the low figure of brucellosis, the free movement of animals across herds could make it a source of infection for other herds. The study also shows that, despite having some understanding about zoonosis, the community's practices are poor. As a result, seropositivity in animals may suggest that brucellosis poses a public health risk. This necessitates a more detailed epidemiological and genomic assessment to identify the specific Brucella species found in the area's animals and humans.



Brucellosis, Ruminants, Risk factors, Seroprevalence, West Shoa, Ethiopia