Seroprevalence of brucellosis and molecular characterization of Brucella spp. from slaughtered cattle in Rwanda

Bovine brucellosis is endemic in Rwanda, although, there is paucity of documented evidence about the disease in slaughtered cattle. A cross-sectional study was conducted in slaughtered cattle (n=300) to determine the seroprevalence of anti- Brucella antibodies using the Rose Bengal Test (RBT), and indirect enzyme-linked immunosorbent assay (i-ELISA). Corresponding tissues were cultured onto a modified Centro de Investigación y Tecnología Agroalimentaria (CITA) selective medium and analysed for Brucella spp. using the 16S-23S ribosomal interspacer region (ITS), AMOS, and Bruce-ladder PCR assays. The RBT seroprevalence was 20.7% (62/300), and 2.9% (8/300) with i-ELISA and 2.9% (8/300) using both tests in parallel. Brucella specific 16S-23S ribosomal DNA interspace region (ITS) PCR detected Brucella DNA in 5.6% (17/300; Brucella culture prevalence). AMOS-PCR assay identified mixed B. abortus and B. melitensis (n=3), B. abortus (n=3) and B. melitensis (n=5) while Bruce-ladder PCR also identified B. abortus (n=5) and B. melitensis (n=6). The gold standard culture method combined with PCR confirmation identified 5.6% Brucella cultures which is higher than the more sensitive seroprevalence of 2.9%. This emphasizes the need to validate the serological tests in Rwanda. The mixed infection caused by B. abortus and B. melitensis in slaughtered cattle indicates cross-infection and poses a risk of exposure potential to abattoir workers. It is essential to urgently strengthen the national bovine brucellosis control program through vaccination as well as test- and-slaughter.