Fig. 1.
Sarcocystis neurona tissue cysts from formalin fixed, paraffin-embedded brain and heart from sea otter #1 (SO1), stained with H&E. A) Hippocampus; densely packed neurons extend from top to bottom in the center of the figure together with two, 30 to 40 μm diameter, thick-walled protozoal tissue cysts (arrows) (bar = 100 μm). B) Higher magnification view of a 45 × 40 μm tissue cyst from the brain of SO1, demonstrating the 2.5 μm thick, pink to amphophilic cyst wall with fine surface villi. Within the cyst are hundreds of 3 to 5 μm diameter bradyzoites, characterized by an outer rim of pale basophilic cytoplasm and a central round, deeply basophilic nucleus (bar = 50 μm). C) Cardiac myofiber from SO1 containing a 175 × 40 μm tissue cyst. Note the presence of fine surface villi and numerous bradyzoites (bar = 65 μm).