Journal of Immunology and Immunopathology

The efficiency of diagnosing subclinical bovine babesiosis using conventional microscopy and PCR-based molecular technique was compared in 206 cattle blood samples collected from five different states of North India. PCR-based assay targeting RAP-1 gene and a nested-PCR targeting 18S rRNA gene of Babesia bigemina were laboratory standardized and used to detect B. bigemina in the DNA extracted from all the blood samples. Results revealed that only 6.7% (n=14) samples were B. bigemina positive by examining Giemsa stained blood smears microscopically. RAP-1 gene-based PCR could detect B. bigemina in 23.3% (n=48) samples and 18S rRNA genebased nested-PCR detected the infection in 37.9% (n=78) samples. All the samples that were detected positive by microscopy were also positive in both the PCR assays. Also, all samples detected B. bigemina positive by RAP-1based PCR were also positive by 18S rRNA-based nested-PCR. However, 30 samples that were negative by RAP1-based PCR were detected B. bigemina positive by 18S rRNA-based nested PCR. The results indicate that as compared with microscopy, the PCR-based assays display a higher sensitivity for diagnosing subclinical babesiosis in cattle. In addition, 18S rRNA-based nested-PCR was found to be more sensitive as compared with RAP-1 genebased PCR.