Serum specimens
Bovine whole blood (for serum) was obtained by collecting jugular venous blood into glass tubes during routine brucellosis surveillance in Armenia. Serum was transferred into separate tubes and tested by rose bengal test (RBT). Positive samples were confirmed by complement fixation test (CFT) and enzyme-linked immunosorbent assays (ELISA), and stored at -20oC. Several negative and positive sera were pooled together to produce negative and positive batches. In order to limit the risk of bacterial contamination, all the sera used were filtered through 0.22µm PVDF low protein binding filter (Millipore, Sigma) before the preparatory step. Pooled serum was tested by RBT before and after filtration.