What is the typical size range of Cyclospora cayetanensis oocysts?

• A. 4–6 μm
• B. 8–10 μm
• C. 12–14 μm
• D. 20–30 μm

Answer: (B)

Size is a practical clue used when identifying intestinal coccidia on stool microscopy. Cyclospora cayetanensis oocysts are about 8–10 μm in diameter, placing them larger than Cryptosporidium oocysts (4–6 μm) but smaller than Isospora belli oocysts (20–30 μm). This 8–10 μm range helps differentiate Cyclospora from other parasites you might see on a stained stool smear, especially when combined with staining behavior and other features like autofluorescence under UV light. So, the typical size range is 8–10 μm. The other options align with different organisms: 4–6 μm corresponds to Cryptosporidium, 12–14 μm is not typical for Cyclospora, and 20–30 μm matches Isospora belli.