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

Subclinical infections of bovine babesiosis, caused primarily by Babesia bi gemina or Babesia bovis are a challenge to current diagnostic methods. In t his study, the development and evaluation of a PCR test for sensitive and s pecific detection of B. bigemina or B. bovis is described. The target selec ted for amplification is part of the apocytochrome b gene, conserved in bot h Babesia spp. and located on the linear similar to 6.0 kb extra chromosoma l 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 infec ted cattle. Analysis of DNA extracted from blood samples drawn from the exp erimental cattle in a blind study revealed an overall sensitivity of 85 and 64% for B. bovis and B. bigemina respectively, while the specificity was 9 7% for B. bovis and 91% for B. bigemina. The test results were compared wit h the recently developed ribosomal DNA-based polymerase chain reaction (PCR ) test and to the complement fixation test for bath Babesia spp. The extra chromosomal DNA-based test was 20% more sensitive than that of ribosomal DN A-based tests. This test may be a more desirable alternative to the current ly used, complement fixation test. (C) 1999 Academic Press.