RESUMEN
A frozen-stored blood clot of a wild brown bear cub Ursus arctos yesoensis that had been captured in Hokkaido, Japan was examined for piroplasma infection using polymerase chain reaction (PCR). Two 18S ribosomal RNA gene (SSU rDNA) sequences were generated. One 1565-bp sequence showed the highest similarity with B. gibsoni (95.9% identity) but, phylogenetically, was found to belong to a distinct lineage. The other sequence (1709-bp) could not be definitively assigned to a described taxon, sharing only limited homology to the closest named species (90.1% identity with C. felis). In order to enhance information obtained from the SSU rDNA sequence, further detection and sequence analysis of the CCTeta gene sequence were done revealing the simultaneous presence of three closely related genotypes (all in a monophyletic lineage) within a single bear host. This finding suggested the possibility that a new Babesia species (Babesia sp. UR1) might have been maintained in nature in wild brown bears. While the parasite's biology is yet unknown, to our knowledge, this is, excepting the single case documentation in 1910 of a hemoparasite in a bear at Russian zoo, the first reported case of piroplasms inhabiting a bear species.
