A stool examination shows eggs with a characteristic lateral spine. The most appropriate treatment for this infection, and its mechanism of action, is:

• A Praziquantel — increases cell membrane permeability to calcium, causing spastic paralysis and tegmental damage in schistosomes ✓
• B Albendazole — inhibits tubulin polymerization reducing glucose uptake in trematodes
• C Oxamniquine — alkylates DNA of schistosomes and causes muscular contraction followed by hepatic shift
• D Metrifonate — organophosphate cholinesterase inhibitor that paralyses Schistosoma haematobium

Explanation

Eggs with a lateral spine are characteristic of Schistosoma mansoni. Praziquantel is the drug of choice for all schistosome species; its mechanism involves increasing permeability of the tegument to calcium ions, causing tetanic muscle contraction, paralysis, and disintegration of the worm's tegument, followed by immune-mediated destruction. Albendazole acts on tubulin polymerization and is used for nematodes/cestodes, with limited activity against trematodes. Oxamniquine is historically used for S. mansoni only; metrifonate was used only for S. haematobium and is now obsolete.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.