Genotypically unique Babesia spp. isolated from reindeer (Rangifer tarandus tarandus) in the United States.

Two morphologically dissimilar Babesia spp. were cultured from reindeer (Rangifer tarandus tarandus) in Placer County, Calif. The smaller isolate, designated RD61, was morphologically similar to Babesia odocoilei. Serum from RD61-infected reindeer reacted equally strongly to B. odocoilei and RD61 parasites in the indirect fluorescent antibody (IFA) test. Small subunit ribosomal RNA (SSU rRNA) gene-sequence analysis showed 99.0% identity to that of B. odocoilei. The larger piroplasm, designated RD63, resembled larger babesia organisms, such as Babesia caballi and Babesia bigemina. Serum from RD63-infected reindeer also reacted with both B. odocoilei and RD61 parasites in the indirect fluorescent antibody test. The SSU rRNA gene showed 94.2% identity to that of B. bigemina. Further studies are needed to determine whether these parasites are the same as the Babesia spp. previously documented in Siberian reindeer.