Comparative diagnosis of ovine brucellosis using single step blood-PCR with old and new serological tools

Brucellosis is an important disease affecting mainly sheep and goats. Diagnosis based on isolation of Brucella organisms from the suspected animals is the golden standard but has a limited sensitivity, expensive and unpractical to apply on a large scale in control campaigns. Accordingly, the indirect diagnosis of disease based on serological tests is the method of choice in the eradication programs. In this study, a single step polymerase chain reaction (PCR) was used to diagnose brucellosis using sheep whole blood and compared its sensitivity and specificity against some of the most commonly used serological techniques and modified ones. Three hundred apparently healthy ewes were randomly chosen from different governorates of Egypt. Sera were tested against Rose Bengal test (RBT), Serum Agglutination test (SAT), ELISA using both the whole Brucellaantigen (W-ELISA) and the periplasmic protein antigen (P-ELISA). Results showed that 39% of the blood samples were positive to the PCR test, Meanwhile 29.3, 27.0, 28.7 and 28.3% were positive to the previous serological tests respectively. We recommend the use of this blood PCR assay for accurate diagnosis of ovine brucellosis especially in the early stage of infection, which is difficult to achieve by the applied serological tests.   Key words: Ovine brucellosis, Blood PCR, RBT, SAT, ELISA.