Development of TaqMan-based real-time PCR assays for diagnostic detection of Babesia bovis and Babesia bigemina.

Two TaqMan-based real-time polymerase chain reaction (PCR) assays devised for the detection of two bovine Babesia parasites, Babesia bovis and B. bigemina, were evaluated for their diagnostic utility using cultured parasites and 92 field bovine blood samples collected from cattle living in Brazil. The real-time PCR assays were compared with previously established nested-PCR assays. The detection limits of both B. bovis- and B. bigemina-real-time PCR assays were identical at the value of 2.5 parasites/microL of the infected blood. When 92 field bovine blood samples were tested using the real-time assays, B. bovis-positive signals were observed in 30 samples among 31 B. bovis-positive blood samples in the nested-PCR assay (96.9% sensitivity and 100% specificity), whereas the B. bigemina-real-time PCR assay could detect the parasite from all of 45 B. bigemina-positive blood samples in the nested-PCR assay (100% sensitivity and specificity). The real-time assays using the TaqMan-system can therefore be practically implemented in the epidemiologic survey for bovine babesiosis. Further studies will be necessary to investigate the clinical value of this technique, especially for the quantitative detections of the parasites.