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Diphyllobothriasis — SCE Infectious Diseases MCQ

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ModerateParasitologyDiphyllobothriasisSCE Infectious Diseases

A 22-year-old woman returns from a gap year in South-East Asia with chronic urticaria, abdominal discomfort, and eosinophilia (2.8 × 10⁹/L). Stool examination shows large (60–75 µm) bile-stained eggs with an operculum and a small knob at the opposite end. What is the most likely organism?

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Correct answer: D — Diphyllobothrium latum (fish tapeworm)

Large operculated eggs (60–75 µm) with a small knob (abopercular knob) at the opposite end from the operculum are characteristic of Diphyllobothrium latum, the fish tapeworm. It is acquired from eating raw freshwater fish (common in South-East Asia, Scandinavia, and Japan). D. latum causes vitamin B12 deficiency (megaloblastic anaemia) through competitive absorption. Treatment is Praziquantel 25 mg/kg single dose or Niclosamide.

Reference: WHO 2023 – Cestode infections; UKHSA 2024 – Imported helminth infections