skip to main content

Cyclosporiasis — SCE Infectious Diseases MCQ

Instant feedback + full explanation. One question, done properly.

ModerateParasitologyCyclosporiasisSCE Infectious Diseases

A 28-year-old man presents with 3 weeks of painless watery diarrhoea and weight loss. He has recently returned from Nepal. Stool microscopy shows acid-fast oocysts of 8–10 µm diameter. He is HIV negative and immunocompetent. What is the most likely organism?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Cyclospora cayetanensis

Acid-fast oocysts of 8–10 µm in a traveller from South Asia are characteristic of Cyclospora cayetanensis (Cryptosporidium oocysts are smaller at 4–6 µm; Cystoisospora are larger at 20–30 µm). Cyclosporiasis presents with watery diarrhoea, fatigue, and weight loss. Treatment is Co-trimoxazole 960 mg BD for 7 days. In immunocompetent patients it is usually self-limiting but treatment speeds recovery.

Reference: UKHSA 2023 – Parasitic infections; WHO 2023 – Cyclosporiasis guidelines