Sarcocystis

• These species follow heteroxenous obligatory prey-predator lifecycle involving animal which are prey in nature as intermediate host and animal which are predator in nature as definitive host.
• Sarcocysts are terminal asexual stage found encysted, primarily in striated muscles of mammals, birds and poikilothermic animals. Also found in cells and in Purkinje fibers of heart and muscles bundles.
• Sarcocyst are either microscopic or macroscopic.
• Macroscopic sarcocyst are found always in skeletal muscles or oesophageal muscles and appear filamentous, globular, spindle or like rice grain.
• Micro-sarcocyst varies from very long and narrow to short and wide.
• More than one cyst may be found in one host cell. These contain cyst wall surrounding parasitic meterocyte or zoite stage.
• Immature sarcocysts contain globular parasites called metrocytes (mother cells). Each metrocyte produce two progenies by endodyogeny. Some metrocytes, through endodyogeny, produce banana-shaped zoites called bradyzoites.
• Live sarcocyst are probably fluid-filled with metrocytes and bradyzoites moving within.
• About 130 species of sarcocystis are recognized.