Cultivation and Phylogenetic Characterization of a Newly Recognized Human Pathogenic Protozoan

An intraerythrocytic protozoan (WA1) recently isolated from a patient in Washington State was shown to be morphologically identical to Babesia microli but biologically and genetically distinct. Continuous growth of WA1 was established in stationary erythrocyte cultures. Hybridization of a chemiluminescent Babesia-specific DNA probe to Southern blots of restriction enzyme-digested genomic DNA showed that WA1 could be distinguished from other Babesia species that were antigenically cross-reactive (Babesia gibsoni and babesial parasites from desert bighorn sheep, Ovis canadensis nelsoni) or known to infect humans (B. microli, Babesia divergens, and Babesia equip, or both