Paragonimiasis — DTM&H MCQ

Correct answer: D — Praziquantel

Praziquantel (option C) is the correct answer. This vignette describes paragonimiasis, lung fluke infection acquired by eating raw or undercooked freshwater crab or crayfish containing Paragonimus metacercariae, endemic to parts of the Philippines and East Asia. The chronic cough, haemoptysis and eosinophilia mimic tuberculosis, but the operculated eggs in sputum are diagnostic of a trematode infection rather than mycobacterial disease. Praziquantel is the recommended anthelmintic for trematode (fluke) infections including paragonimiasis, acting by increasing cell membrane permeability to calcium in the parasite, causing paralysis and death of the fluke, with a short multi-day regimen giving high cure rates. Why the other options are wrong: C. Rifampicin monotherapy: this is an antituberculous agent; although paragonimiasis can radiologically and clinically mimic TB, there is no mycobacterial infection here, and the operculated eggs confirm a helminthic cause, so antituberculous therapy is inappropriate and would fail to clear the fluke. E. Chloroquine: this is an antimalarial used for chloroquine-sensitive Plasmodium species and some autoimmune conditions, it has no activity against trematodes and would not affect Paragonimus. A. Cefalexin: a cephalosporin antibiotic targeting bacterial cell wall synthesis, it has no role against a parasitic fluke infection and would not address the underlying cause of haemoptysis or eosinophilia. B. Fluconazole: an antifungal (azole) that inhibits ergosterol synthesis, entirely irrelevant to trematode infection, this presentation is not fungal. Key point: Chronic cough with haemoptysis, eosinophilia and operculated eggs in sputum after eating raw freshwater crab or crayfish points to paragonimiasis, a TB mimic treated with praziquantel.

Reference: PMC (Keiser J, Utzinger J), Praziquantel Treatment in Trematode and Cestode Infections: An Update, describing praziquantel dosing regimens for Paragonimus species (lung fluke) infection, https://pmc.ncbi.nlm.nih.gov/articles/PMC3780935/