Development and evaluation of an extra chromosomal DNA-based PCR test for diagnosing bovine babesiosis.

Subclinical infections of bovine babesiosis, caused primarily by Babesia bigemina or Babesia bovis are a challenge to current diagnostic methods. In this study, the development and evaluation of a PCR test for sensitive and specific detection of B. bigemina or B. bovis is described. The target selected for amplification is part of the apocytochrome b gene, conserved in both Babesia spp. and located on the linear approximately 6.0 kb extra chromosomal DNA. The test was evaluated to detect the parasites over a period of 5 (B. bigemina) and 10 months (B. bovis) post infection in experimentally infected cattle. Analysis of DNA extracted from blood samples drawn from the experimental cattle in a blind study revealed an overall sensitivity of 85 and 64% for B. bovis and B. bigemina respectively, while the specificity was 97% for B. bovis and 91% for B. bigemina. The test results were compared with the recently developed ribosomal DNA-based polymerase chain reaction (PCR) test and to the complement fixation test for both Babesia spp. The extra chromosomal DNA-based test was 20% more sensitive than that of ribosomal DNA-based tests. This test may be a more desirable alternative to the currently used, complement fixation test.