In routine stool microscopy, which type of organism is typically detected by eggs or larvae?

• A. Protozoa
• B. Helminths
• C. Bacteria
• D. Fungi

Answer: (B)

Stool microscopy relies on finding life stages that are shed by the parasite into feces. Eggs and larval forms are classic for helminths, the worm parasites. These organisms produce eggs or larvae that pass into stool and can be visualized with concentration techniques and microscopy, allowing diagnosis of infections caused by nematodes, cestodes, and trematodes. Protozoa, on the other hand, are usually detected by their cysts or trophozoites, not eggs or larvae. Bacteria and fungi are identified by other methods such as culture, staining, or direct visualization of their typical forms, not by eggs or larvae. So, when eggs or larvae are seen in routine stool microscopy, it points to helminth infections.