Molecular Detection of Brucella Species Causing Abortion Outbreaks in Ruminant Livestock in Tunisia

Brucellosis is an endemic zoonotic disease in Africa and Tunisia, severely affecting both human and animal health, particularly ruminants. In livestock, brucellosis causes reproductive failure, including abortions, leading to substantial economic losses. Despite surveillance and vaccination efforts in Tunisia, brucellosis remains widespread. This study is aimed at assessing the presence of Brucella infection in aborted animals (sheep, goats, and cattle) using an IS711-based real-time PCR assay, determining the circulating species (Brucella melitensis and Brucella abortus) by differential qPCR, and identifying the most suitable sample type for detection between 2020 and 2022. Samples including vaginal swabs, blood, placenta, and fetal organs (liver, spleen, stomach, and cotyledons) were collected from farms selected based on abortion reports from farm owners. A total of 272 samples were analyzed, of which 24.26% tested positive for Brucella spp., with 25.71% in sheep, 13.33% in goats, and 8.33% in cattle. The detection rate of Brucella spp. was estimated at 24% (60/250) in aborted females and 27.27% (6/22) in aborted fetal materials. Vaginal swabs exhibited a notable positivity rate of 31.13%, 28.57% in organs and 5.71% in blood. B. melitensis and B. abortus were detected in 46.96% and 19.69% of positive samples, respectively. Interestingly, one sample showed a coinfection with both species; however, neither B. abortus nor B. melitensis was detected in 21 positive samples. This study highlights the presence of Brucella spp. in aborted ruminants and the circulation of B. melitensis and B. abortus, underlining the importance of molecular tools for the reliable diagnosis of brucellosis, and their usefulness in mitigating the spread of this infection on farms by applying appropriate control measures.