Eggs or larvae recovered in the stool are not routinely used to diagnose infections caused by which helminth?

Eggs or larvae recovered in the stool are not routinely used to diagnose infections caused by which helminth?

• A. Strongyloides stercoralis
• B. Trichinella spiralis
• C. Necator americanus
• D. Ascaris lumbricoides

Answer: (B)

Stool testing for eggs or larvae is a common way to diagnose many intestinal helminths because their stages are shed into feces. But Trichinella spiralis follows a different path: after ingestion, the larvae are released in the small intestine, mature into adults, and then migrate to striated muscle where they encyst. There is no ongoing production of eggs or larvae in the gut that would appear in stool, so stool examination is not a reliable diagnostic method for Trichinella. Diagnosis relies on detecting encysted larvae in muscle tissue or using serology. In contrast, parasites like Ascaris lumbricoides and Necator americanus produce eggs that are shed in stool, and Strongyloides stercoralis can be identified by larvae in stool, so stool examination is routinely used for them.

Stool testing for eggs or larvae is a common way to diagnose many intestinal helminths because their stages are shed into feces. But Trichinella spiralis follows a different path: after ingestion, the larvae are released in the small intestine, mature into adults, and then migrate to striated muscle where they encyst. There is no ongoing production of eggs or larvae in the gut that would appear in stool, so stool examination is not a reliable diagnostic method for Trichinella. Diagnosis relies on detecting encysted larvae in muscle tissue or using serology. In contrast, parasites like Ascaris lumbricoides and Necator americanus produce eggs that are shed in stool, and Strongyloides stercoralis can be identified by larvae in stool, so stool examination is routinely used for them.