Abstract
This cross-sectional study was carried out to investigate the status of brucellosis in sheep management under extensive smallholder farming and intensively in governmental breeding ranches in six districts selected from three administrative zones. Using multistage sampling, serum samples of 2409 sheep from 274 flocks were collected and tested using the Rose Bengal Plate Agglutination Test (RBPT) and positive sera were confirmed using a Complement Fixation Test (CFT). Of all animals tested, 4.98% were RBPT positive, and after confirmation with CFT, the overall animal-level prevalence was found to be 4.89% (CI: 3.24-6.9%). Of the flocks sampled, 61 (22.3%, CI: 18.03-29.17%) had at least one animal positive to both tests. Significantly higher (P < 0.001) individual animal seroprevalence of 5.87% (CI: 3.83-7.31%) was found in sheep under smallholder production than in breeding ranches (1.75%, 95% CI: 1.57-3.05%). However, flock level seroprevalence in breeding ranches was found to be 100% (8/8), while in the smallholder production it was 19.92% (CI: 16.4-25.81%). Significantly highest animal-level seroprevalence of 9.55% (CI: 7.91-12.4%) was observed in north Wollo zone's smallholder farms. From the three studied breeding ranches, highest seroprevalence of 3.57% (CI: 2.84%-5.18%) was found in Sheno Agricultural Research Centre. Significantly higher seroprevalence (P < 0.01) was found in aborted sheep and with history of retained fetal membrane in both production systems. All the sheep flocks in the studied breeding ranches were found to be seropositive; hence, this study suggests strict control measures of ovine brucellosis in the breeding reaches, since they could be a source of infection for the smallholder farms.
Highlights
Brucellosis is a zoonotic disease that has a significant economic, social, and public health impact in many parts of the world
At the individual animal level, a total of 2409 sera samples were tested with Rose Bengal Plate Test (RBPT), of which 120 (4.98%) sheep were positive for brucellosis
The RBPT positive serum samples were confirmed by complement fixation test (CFT) with 118 (4.89%, 95% confidence intervals (CI): 3.24-6.9%) of the samples being seropositive for brucellosis upon further testing by Complement Fixation Test (CFT)
Summary
Brucellosis is a zoonotic disease that has a significant economic, social, and public health impact in many parts of the world. Brucellosis is caused by the bacteria of the genus Brucella and Gram-negative intracellular coccobacilli, which occur in a wide variety of animals including cattle, sheep, goats, pigs, and other livestock as well as humans [1]. Nine Brucella species are currently recognized; seven of them that affect terrestrial animals are Brucella abortus, B. melitensis, B. suis, B. ovis, B. canis, B. neotomae, and B. microti and the two other species that affect marine mammals are B. ceti and B. pinnipedialis [2]. Significant reproductive losses are usually caused by Brucella melitensis and Brucella ovis. The prevalence of this disease varies widely from country to country, small ruminant brucellosis is mostly caused by B. melitensis and remains one of the most important zoonotic diseases [3]. Brucella ovis is a nonzoonotic species, which is an important cause of orchitis and epididymitis in sheep, but it is not recognized as a cause of natural infection in goats [4]
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