Abstract:
There is considerable confusion concerning Sarcocystis species in camels. Five species:
Sarcocystis cameli, S. ippeni, S. camelicanis, S. camelocanis, and S. miescheri were named with
inadequate descriptions and no type specimens. Here, we review literature on sarcocystosis in
camels worldwide and redescribe structure of S. cameli and S. ippeni sarcocysts by light and
transmission electron microscopy (LM, TEM). Eight sarcocysts from the esophagi of two camels
(Camelus dromedarius) from Egypt were studied. By LM all sarcocysts were thin walled with barely visible projections on the cyst walls. By TEM, two structurally distinct sarcocysts were
recognized by unique villar protrusions (vp) not found in sarcocysts from any other host.
Sarcocysts of S. cameli had vp of type 9j. The sarcocyst wall had upright slender vp, up to 3.0
μm long and 0.5 μm wide; the total thickness of the sarcocyst wall with ground substance layer
(gs) was 3.5 μm. On each vp there were rows of knob-like protrusions that appeared to be
interconnected. The vp had microtubules that originated at mid point of the gs and continued up
to the tip; microtubules were smooth, without any granules or dense areas. Bradyzoites were
approximately 14-15 x 3-4 μm in size with typical organelles. Sarcocystis ippeni sarcocysts had
type 32 sarcocyst wall characterized by conical villar protrusions with an electron dense knob.
The total thickness of the sarcocyst wall (from the base of gs to vp tip) was 2.3-3.0 μm. The vp
were up to 1.2 μm wide at the base and 0.25 μm at the tip. Microtubules in vp originated at
midpoint of gs and continued up to tip; microtubules were criss-crossed, smooth and without
granules or dense areas. Bradyzoites were 12.0-13.5 x 2.0-3.0 μm in size. Sarcocystis
camelicanis, S. camelocanis, and S. miescheri are considered invalid.
