Ultrastructural study of Sarcocystis fusiformis (Railliet, 1897) infecting the Indian water buffalo (Bubalus bubalis) of Egypt.

Sarcocysts from the muscular layer of the oesophagus of 20 Indian water buffaloes (about 7--10 years old) have been collected in Egypt and studied by means of electron microscopy in Bonn (West Germany). Large and small cysts have been observed. The large type ranged from 7--30 X 3--7 mm, and the small cysts measured 1.3--5.1 X 0.7--2.2 mm. The metrocytes of both types of cysts as well as the merozoites were very similar concerning their shape, size and ultrastructural characteristics. The metrocytes of the large and small cysts were mostly located at the peripheral region of the cysts and multiplied by endodyogeny. They were variable in shape and size. They ranged from 7.6 X 4.8 micrometer to 9.2 X 5.4 micrometer. Most of them exhibited deep invaginations of their pellicle. Their cytoplasm was electron pale and often extremely vacuolated. The merozoites of both types of cysts were elongated with a length ranging from 14.6--17.0 micrometer and showed all characteristic organelles of these cells (conoid, rhoptries, micronemes, subpellicular microtubules etc.) The wall of the large and small cysts showed no distinct morphological differences. The great similarities between the walls of the two types of cysts as well as between the micromorphology of the developmental stages (metrocytes and merozoites) lead to the conclusion that the two types of cysts examined may belong to one species of Sarcocystis.