In Strongyloides stercoralis, which larval form is typically recovered in stool for diagnosis?

• A. Miracidium
• B. Rhabditiform larva
• C. Filariform larva
• D. Oocyst

Answer: (B)

In Strongyloides stercoralis, diagnosis by stool relies on finding the rhabditiform larva. Inside the human host, the adult female in the small intestine produces eggs that hatch into rhabditiform larvae, which are then shed in the stool and can be identified microscopically. This stage is the hallmark of stool-based detection. Miracidium is the larval form of trematodes, not nematodes; oocysts are from coccidian protozoa; the filariform larva is the infective form that typically penetrates the skin and is less commonly seen as a diagnostic stool form. Although some rhabditiform larvae can molt to the autoinfective filariform stage, the classic diagnostic finding in stool remains the rhabditiform larva.