Sarcocystis jorrini sp. nov. from the fallow deer Cervus dama.

Sarcocystis jorrini sp. nov. isolated from the muscle of naturally infected fallow deer (Cervus dama) from the Doñana National Park (Spain) is described by light and electron microscopy. Sarcocysts were macroscopic (2.7 x 1.4 mm) and were found in all striated muscle, including that of the esophagus and the heart. As visualized by light microscopy, the cyst walls were formed by mammilated protrusions surrounded by a coating of connective tissue measuring 10-35 mm in thickness. Electron microscopy revealed that the parasitophorous vacuole was serrated in appearance, with numerous pinocytic vesicles running along its whole length. Villar protrusions were of varying shape and were square, rectangular, or linguiform in cross section. The core of the villi contained small dense granules and microfilaments, which were more abundant in peripheral areas. Ground substance contained larger dense granules clustered around the base of villi. The sarcocyst was surrounded by a secondary cyst wall composed of collagen fibrils and fibrocytes. S. jorrini is the first macroscopically visible sarcocyst of the genus Cervus reported to have a secondary cyst wall.