CHARACTERIZATION OF BOVINE SARCOCYSTIS SPECIES BY ANALYSIS OF THEIR 18S RIBOSOMAL DNA-SEQUENCES

Two Sarcocystis hirsuta isolates from 2 cattle (Bos taurus), 2 Sarcocy stis hominis-like isolates from 2 cattle, 1 each Sarcocystis hominis-l ike isolate from a zoo-born dwarf zebu (B. tauruss) and from a zoo-bor n bison (Bison bison), and I each Sarcocystis cruzi isolate from the d warf zebu and the bison have been characterized by comparing the direc tly sequenced polymerase chain reaction products of their 18S rRNA gen es. Sequences of 2 different isolates from the same species always sho wed a very high, nearly complete identity to each other both within al l or only the conserved overlapping nucleotides. Thus. the 18S rDNA se quences of both S. hirsuta isolates proved to belong to a single speci es. The same is true for all 3 S. cruzi sequences. The 3 S. hominis-li ke isolates could not be placed within a single species using these cr iteria. They formed 2 separate groups (1 cattle isolate and the bison isolate, and the other cattle isolate and the dwarf zebu isolate). The results suggest that zoo-born large mammals do serve as intermediate hosts for Sarcocystis species known from indigenous herbivores, and th at there might be another species found in cattle that is morphologica lly very similar to S. hominis.