Which parasite has lateral-spined eggs observed in stool?

• A. Schistosoma haematobium
• B. Giardia lamblia
• C. Taenia solium
• D. Schistosoma mansoni

Answer: (D)

Eggs with a spine on the side are a hallmark of Schistosoma mansoni. In stool samples, the Schistosoma mansoni egg has a prominent lateral spine, which helps distinguish it from other parasites that also produce eggs but lack this feature. This parasite causes intestinal schistosomiasis, and its eggs are commonly found in feces.

In contrast, eggs of Schistosoma haematobium have a terminal (tip) spine, not a lateral one, and Taenia solium eggs are taeniid eggs with a thick outer shell and an oncosphere inside—not a spinal feature at all. Giardia lamblia yields cysts or trophozoites rather than eggs with spines.