Seroepidemiology and Molecular Identification of Brucella Species in Livestock and Humans in South Omo Zone, South Ethiopia Regional State, Ethiopia
No Thumbnail Available
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Abeba University
Abstract
Brucellosis, a bacterial infection caused by the genus Brucella affecting animals, poses economic and public health risks, particularly for communities reliant on livestock. Limited data exists on the epidemiology of brucellosis and Brucella species affecting livestock and humans in Ethiopia, particularly in the South Omo Zone of the South Ethiopia Regional State. A crosssectional study was conducted in South Omo Zone, Ethiopia, from January 2017 to June 2020 to determine the prevalence, isolate and identify Brucella species in cattle, sheep, goats, and humans, and pinpoint risk factors associated with the disease across five istricts: Bena-Tsemay, Dassenech, Hamer, Gnangatom, and Malie. A multistage sampling approach was used to select study subjects, encompassing 1,920 cattle, 1,536 sheep, 1,536 goats, and 768 humans for serological examiantion using combined serial tests RBPT, competitive ELISA and CFT. These sample sizes for animals, and humans were distributed to each district in proportion to their livestock,and human populations, respectively. Additionally, a structured questionnaire survey was conducted to explore risk factors associated with brucellosis in both livestock and humans. Furthermore, a total of 340 clinical specimens (n=53 milk from cattle, n=39 milk from goats, n=28 milk from sheep, n=34 vaginal swab from cattle, n=48 vaginal swab from goats, n=16 vaginal swab from sheep) having recent history of abortion and whole blood samples from pastoralists with febrile illness visiting health centers (n=122) were ollected for Brucella species isolation and molecular identification using real-time polymerase chain reaction. Data were analyzed with STATA version 14.0, applying logistic regression to assess risk factors associations. The findings revealed that in cattle, overall seroprevalence of 5.26% (95% CI:5.05-8.04) and
36.43% (95% CI:33.18-43.76) at individual and herd level, respectively. Age, sex, herd size, abortion history, retained fetal membrane, and parity were statistically significant with seropositivity for brucellosis. Moreover, the findings established that pastoralists had low level of awareness about brucellosis and carryout risky practices that could expose them to brucellosis. In sheep, the study indicated 5.40% (95% CI: 3.34-7.47) and 39.74% (95% CI: 36.50-48.80) seroprevalence at individual and flock level, respectively. Age groups, sex, flock size, district, history of abortion, and body condition were stastistically significantly associated risk factors with Brucella seropositivity (P<0.05). In goats, individual animal level and flock level seroprevalences were recorded as 6.90% (95% CI:5.18-10.90) and 34.31% (95% CI:30.52- 42.41), respectively. Statistically significant associations were found between seroprevalence
and factors such as sex, age, flock size, body condition, parity number, production system, history of abortion, retained fetal membrane, and stillbirth (P< 0.05). In humans, the overall seroprevalence of brucellosis recorded was 14.58% (95% CI: 12.07-18.24). The multivariable logistic regression analysis indicated statistically significant association (P<0.05) between Brucella seropositivity and factors such as gender, age, education level, occupation, consumption of raw animal products such as milk, meat and blood, direct animal contact, assisting animals during parturition with bare hand, contact with aborted materials without
protective gloves, and lack of knowledge of zoonosis and brucellosis. The isolation and molecular detection revealed that 15 Brucella isolates were obtained (4.41%): 8 B. melitensis (53.33%) from (3 goats’ milk sample, 3 goats’ vaginal swab samples, and 2 human blood); 5 B. abortus (33.33%) from (2 cattle milk, 1 cattle vaginal swabs, and 2 human blood); and 2 B. ovis (13.33%) both from vaginal swab of sheep based on bacteriological and biochemical tests. The isolation and molecular identification of these Brucella species from multiple hosts including humans demonstrate potential cross-species transmission. In conclusion, brucellosis is endemic in both livestock and humans in South Omo Zone, driven by multiple risk factors and exacerbated by low community awareness. The findings underscore a serious public health concern requiring urgent need for integrated control measures, including public education, improved veterinary services, safe handling of animal products, and further research on disease transmission dynamics in wildlife-livestock-human interfaces.
Description
Keywords
Brucella species, Ethiopia, Isolation and molecular identification, Livestock, Public Health. Seroepidemiology, South Omo zone.