Which statement about the rhabditiform larvae of Strongyloides stercoralis is correct?

Which statement about the rhabditiform larvae of Strongyloides stercoralis is correct?

• A. Are infective for humans
• B. Are the diagnostic form found in feces
• C. Are the diagnostic form found in blood
• D. Are found in the urine

Answer: (A)

The key idea is that the rhabditiform larva of Strongyloides stercoralis is not the infectious stage. Infection occurs when filariform (infective) larvae in soil penetrate the skin, initiating the lifecycle. The rhabditiform larva is the noninfective, diagnostic form typically found in feces; it’s the stage most often used to diagnose Strongyloides infection in standard stool examinations. So saying these larvae are the infective form is not correct. They are not the diagnostic form in blood or urine in routine practice; those specimens are not relied upon for standard diagnosis, though in severe hyperinfection larvae can appear in various tissues.