Identification of piroplasm infection in questing ticks by RLB: a broad range extension of tick-borne piroplasm in China?

Sensitive and specific diagnostic method for rapid and simultaneous detection and discrimination of the different species is needed for an effective control of piroplasmosis. Here, a reverse line blot (RLB) assay was developed for piroplasm detection. A general pair of primer based on 18S ribosomal RNA (rRNA) gene was used to amplify V4 region of 18S rRNA gene. General and specific probes for 13 piroplasm species were cited from previous publications or designed according to the alignment of 18S rRNA gene sequences. For sensitivity test of RLB assay, serially diluted plasmids of the different species were used to access the sensitivity of the RLB. Four hundred and fifty tick samples collected from grass from different provinces of China were then detected. The result indicated that the RLB assay is highly specific and sensitive, detecting up to 10(2) copies/μl of recombinant plasmid DNA. Multiple piroplasms were detected as single or mixed infection from tick species. Eight piroplasm species, most of which were Theileria annulata (33/450, 7.3 %) or Babesia sp. Xinjiang (30/450, 6.7 %), were found to infect with 89 tick samples in four tick species; no infections with Babesia major, Babesia ovata, Babesia bigemina, Theileria sergenti, or Theileria equi were detected. The piroplasms species-specific RLB assay may have potential clinical application in the simultaneous detection and differentiation of Babesia and Theileria species.