Figure 1. Unrooted phylogenetic tree for the complete 18S rRNA gene of selected Babesia spp. The tree was computed by using the quartet puzzling maximum likelihood method of the TREE-PUZZLE program. The scale bar indicates an evolutionary distance of 0.01 nucleotide substitutions per position in the sequence. The GenBank accession numbers for the sequences used in the analysis are as follows: B. divergens (6), AY046576; B. odocoilei, AY046577; Babesia sp. EU1 (6), AY046575; the Babesia sp. from the patient in Washington State, AY274114 (see arrow); B. microti, U09833; WA1, from the index case of infection with WA1-type parasites (7,8), AF158700; and Theileria annulata, M64243.