In a survey for sarcocysts in muscle tissues obtained from 142 water buffaloes (Bubalus bubalis）, 92(64.8%) carcasses had sarcocysts. Macroscopic and two forms of microscopic cysts, the spindle-shaped or fusiform cysts commonly occurring in the muscles of the esophagus, throat and limbs, and the globular to oval cysts which were the dominant form in the diaphragm and the cervical muscle tissue were noted. Ultrastructural analysis of macroscopic and microscopic cysts and their cyst wall revealed two distinct species of Sarcocystis infecting Philippine water buffaloes. These are the macroscopic species, Sarcocystis fusiformis which has been previously reported in the country possessing highly-dendritic cauliflower-like projections emanating from the primary cyst wall, with annulated microfibrils and numerous electron dense granules; and the newly redescribed Sarcocystis levinei (Dissanaike and Kan 1978; Huong, Dubey and Uggla 1997) exhibiting a cyst wall with numerous, minute hair-like villar protrusions with expanded or dome-shaped base, an intermediate finger-like, and distal tapering segments which at some points join to form conical tufts. Our findings represent the first report of S. levinei in Philippine water buffaloes are developing forms of S. fusiformis. Three morphologically different microscopic sarcosyt were detected; the spherical and radially striated or hirsute cysts with thick cyst wall (type 1); the spherical to oval exhibiting thinner cyst wall (type 2) compared to type 1; and the spindle shaped to elongate cysts with prominent compartmentalized arrangement of zoites separated by septate. Sarcocysts morphology and their host location suggest Sarcocystis hominis and Sarcocystis cruzi as the most likely etiologic species. The infections noted may either be local or imported in origin. In the absence of any documentes studies on local or imported bovine sarcocystosis in the country to date, these initial findings are valuable. However, future studies on ultrastructural analysis of the sarcocysts and the cyst wall to confirm species identification, and experimental exposure studies to determine the probable definitive host(s) of Sarcocystis species are necessary
