Study of Brucella abortus Infection Using Serological Test and Polymerase Chain Reaction (PCR) in Dairy Cattle

Abstract

Brucellosis is an important zoonotic disease for public and animal health that causes significant economic losses. Widely applied brucellosis detection method are Rose bengal test (RBT) and complement fixation test (CFT) as screening and confirmation tests, respectively. This study was aimed to detect of Brucella abortus infection using serological and molecular tests, i.e., milk ring test (MRT), RBT, CFT, enzyme linked immunosorbant assay (ELISA), and polymerase chain reaction(PCR). Milk, blood and serum were collected from a total of 64 dairy cattle with history of decreased milk production, vaccination, abortion, hygroma and retentio secundinae. The result showed that 64%, 34%, 45% and 26% samples were positive tested by MRT, RBT, CFT, and ELISA, respectively. The Kappa analysis showed that the confirmation CFT has poor to good agreement of 0.249, 0.511, and 0.710 with MRT, ELISA and RBT, respectively. None of blood and milk samples from serologically positive cattle were tested positive by PCR that could be due to the absence of bacteremia and bacterial shedding in milk. This finding suggests the presence of chronic infection among the studied animals, which characterized by high antibody levels in the absence of bacteria in the blood. Application of MRT and ELISA tests in parallel would increase the test sensitivity, while application of CFT and ELISA test or RBT and CFT in serial would increase the test specificity.