Identification of Sarcocystis hominis-like (Protozoa : Sarcocystidae) cystin water buffalo (Bubalus bubalis) based on 18S rRNA gene sequences

DNA templates were extracted from isolates of Sarcocystis hominis-like cyst s collected from cattle and water buffalo, as well as from Sarcocystis fusi formis cysts and Sarcocystis suihominis cysts. The 18S rRNA genes were ampl ified using DNA from a single cyst as the templates. Approximately 1,367-1, 440 bp sequences were obtained. The sequence difference in isolates of Sarc ocystis hominis-like cysts from water buffaloes. and isolates of S. hominis cysts from cattle were very low, only about 0.1%, much lower than the lowe st value (1.7%) among different species. Combined with their morphological structure, these sequence data indicate that the 4 isolates from cattle and water buffalo might be the same species. i.e.. S. hominis, suggesting that both cattle and water buffalo may serve as the intermediate hosts for this parasite. Apparently, this is the first report using a single cyst to do s uch work and is a useful way to distinguish the Sarcocystis cyst in an inte rmediate host that may be simultaneously infected by several different Sarc ocystis species.