Urogenital schistosomiasis — DTM&H MCQ
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Correct answer: A — Praziquantel 40 mg/kg as a single dose
The correct answer is A, praziquantel 40 mg/kg as a single dose. The stem describes classic urinary schistosomiasis (Schistosoma haematobium): a child in Egypt with freshwater exposure in irrigation canals, painless terminal haematuria for months, and eggs with a terminal spine on urine microscopy. Praziquantel is the drug of choice for all Schistosoma species and acts by increasing tegumental permeability to calcium, causing spastic paralysis and detachment of the worm from the venous plexus, followed by immune clearance. A single oral dose of 40 mg/kg is highly effective against adult flukes and is the regimen recommended in UK practice for schistosomiasis. Untreated chronic S. haematobium infection causes bladder wall fibrosis, hydronephrosis, and is a recognised risk factor for squamous cell carcinoma of the bladder, making treatment essential even in mild presentations. Why the other options are wrong: E. Metronidazole 400 mg three times daily for 5 days: this is used for anaerobic and protozoal infections such as giardiasis, amoebiasis and trichomoniasis, not for trematode (fluke) infections; it has no activity against Schistosoma. D. Niclosamide 2 g as a single dose: this is a taeniacide used for tapeworm (cestode) infections such as Taenia saginata or Taenia solium, not for blood flukes. B. Albendazole 400 mg as a single dose: this is a benzimidazole active against soil-transmitted helminths (roundworm, hookworm, whipworm) and some cestodes, but it is not effective against schistosomes. C. Ivermectin 200 microgram/kg as a single dose: this treats strongyloidiasis, onchocerciasis and other nematode infections; it has no schistosomicidal activity. Key point: terminal-spined ova plus terminal haematuria after freshwater exposure signals S. haematobium, treated with single-dose praziquantel 40 mg/kg regardless of species.
Reference: BNF (NICE), Praziquantel, Indications and dose (schistosomiasis): https://bnf.nice.org.uk/drug/praziquantel.html