Seroprevalence, characterization, and risk factors of brucellosis in cattle, sheep, goats, and camels in the Oromia region, Borena Zone, Ethiopia

Abstract

Brucellosis is a significant issue in the Borena Zone of Ethiopia, causing economic losses due to decreased milk production, abortions, infertility, and weak offspring. However, it is underreported and adequately addressed in the region. A cross-sectional study was conducted in the Gomole and Dhas districts of the Borena Zone in Ethiopia between November 2022 and June 2023 to estimate the seroprevalence of brucellosis in livestock. The study included cattle, camels, sheep, and goats, with random sampling at the individual and herd levels. A total of 490 cattle, 160 camels, and 330 each of sheep and goats were tested for seroprevalence. Random sampling was done on farms within the peasant association to test livestock at the individual and herd levels. Blood samples were collected from 490 cattle, 160 camels, and 330 each from sheep and goats. Samples were screened with the rose Bengal test (RBT) confirmed with the indirect enzyme-linked immunosorbent assay (iELISA). Polymerase chain reaction (PCR) detected Brucella species in blood clot samples collected from seropositive animals. The highest prevalence was observed in goats, with individual and herd-level rates of 10.0 % and 56.7 %, respectively. In contact, cattle had the lowest prevalence, 1.4 % at the individual level and 23.0 % at the herd level. Both B. abortus and B. melitensis were detected in cattle, sheep, and camels, while B. melitensis was the most common species found in goats. Statistically significant differences in brucellosis prevalence were observed among species, with the highest rates in the Gomole district compared to Dhas. Female animals had a higher prevalence than males, especially those with a history of abortion. Logistic regression showed that district and host species were associated with Brucella infection, with Gomole herds at higher risk. Brucella melitensis infections were common in sheep, camels, and goats, while B. abortus infections were mainly in cattle, with mixed infections in all species except sheep. Brucella melitensis infections were common in sheep, camels, and goats in the Oromia pastoral community, while B. abortus infections were mostly seen in cattle, with mixed infections in all species except sheep.