Comparison of the internal transcribed spacer, ITS-1, from Sarcocystis falcatula isolates and Sarcocystis neurona

The genetic diversity among 6 Sarcocystis falcatula isolates derived from g eographically distinct regions in the U.S.A. was detected using the first i nternal transcribed spacer region 1 (ITS-I) of the rRNA gene. These sequenc es were then compared to the full sequence from a Sarcocystis neurona isola te obtained from a California horse diagnosed with equine protozoal myeloen cephalitis. No nucleotide differences were detected over partial sequence a nalysis of 2 additional S. neurona isolates; however. the complete nucleoti de sequence for the ITS-I region was not compared. Twelve nucleotide differ ences were consistently detected when aligned sequences of S. neurona were compared to those of the S. falcatula isolates. Additional nucleotide base changes were detected among the S.falcatula isolates, but these changes wer e not consistent in all the S. falcatula isolates. These results indicate t hat S. falcatula may be comprised of a heterogeneous population and that th e ITS-I region can be used to distinguish S. neurona from S. falcatula used in this study.