What is the primary diagnostic feature of Schistosoma mansoni eggs in stool?

• A. Terminal spine
• B. Lateral spine
• C. Operculated
• D. No spine

Answer: (B)

The main concept is recognizing Schistosoma eggs by spine position. Schistosoma mansoni eggs in stool have a prominent spine on the lateral side of the egg, which is the distinctive feature used to diagnose intestinal schistosomiasis caused by mansoni. This lateral spine sets it apart from other species: the bladder-dwelling S. haematobium eggs have a terminal spine and are usually found in urine, while S. japonicum eggs are smaller and have a less conspicuous or absent spine. Therefore, spotting a lateral spine in stool aligns with Schistosoma mansoni and supports that diagnosis.