Figure 1. Oocysts of Sarcocystis spp. from patients with human intestinal sarcocystosis, France, 2021–2024. A) Concentrated stool smear stained using the merthiolate-iodine-formaldehyde method. Sporulated oocysts are colorless and contain 2 elongated sporocysts. The oocyst wall is thin and often invisible in wet mount. B) Wet mount. Each sporocyst contains 4 banana-shaped sporozoites and a granular sporocyst residuum, which may be compact or dispersed. The 4 sporozoites are rarely seen in a single plane of focus. C) Fresh homogenized stool smear under fluorescent microscopy. Individual sporocysts are autofluorescents and will appear blue with an excitation filter of 330–365 nm. Scale bars indicate 10 µm.