Rhabditiform larvae seen in stool are diagnostic of which parasite?

• A. Enterobius vermicularis
• B. Strongyloides stercoralis
• C. Ascaris lumbricoides
• D. Ancylostoma duodenale

Answer: (B)

Rhabditiform larvae in stool point to Strongyloides stercoralis because this parasite sheds its rhabditiform larval form directly into the intestinal contents, which can be recovered from fecal samples. This larval stage is distinctive and serves as the diagnostic clue for infection.

In contrast, the other parasites have different common diagnostic cues: Enterobius vermicularis is usually diagnosed by eggs collected from perianal skin (sticky-tape test), not by larvae in stool. Ascaris lumbricoides and Ancylostoma duodenale are typically diagnosed by eggs found in stool rather than rhabditiform larvae. The presence of rhabditiform larvae in stool is a classic hallmark of Strongyloides infection.