Cystic echinococcosis — DTM&H MCQ

Correct answer: D — Echinococcus serology with specialist imaging review

The correct answer is D, Echinococcus serology with specialist imaging review. The ultrasound description of daughter cysts and floating membranes in a hepatic cyst, in a shepherd from a sheep-rearing endemic region, is classic for cystic echinococcosis (hydatid disease) caused by Echinococcus granulosus, and mild eosinophilia supports this. UK guidance for eosinophilia in returning travellers and migrants recommends confirming suspected hepatic hydatid disease with serology combined with compatible ultrasound and MRI appearances, since serology is not invariably positive and imaging staging (WHO IWGE classification) guides management. Cases should then go to a specialist hydatid multidisciplinary team, as unsupervised intervention carries serious risk. This combined, specialist-led approach is the correct next step rather than any single crude test. Why the other options are wrong: B. Stool microscopy for tapeworm eggs: humans are accidental intermediate hosts harbouring the larval cyst stage, not the adult tapeworm, so no eggs are shed in human stool; this test is relevant to dogs (definitive hosts), not to diagnosing human hydatid disease. C. Blood film for microfilariae: this investigates lymphatic filariasis or loiasis, which present with lymphoedema, chyluria, or Calabar swellings, not cystic hepatic lesions with daughter cysts. E. Percutaneous diagnostic aspiration in clinic: uncontrolled aspiration of a hydatid cyst risks anaphylaxis and peritoneal dissemination of protoscoleces; any percutaneous sampling must only occur within a specialist PAIR pathway with anaphylaxis cover, not opportunistically in clinic. A. Widal test for enteric fever: this detects antibodies to Salmonella Typhi/Paratyphi causing prolonged fever with abdominal symptoms, not a cystic hepatic mass; it is also notoriously unreliable and not aligned with the ultrasound findings here. Key point: Daughter cysts and floating membranes on ultrasound in an endemic-exposure patient signal hydatid disease, which is confirmed by serology plus specialist imaging review, never by blind aspiration.

Reference: UK guidelines for the investigation and management of eosinophilia in returning travellers and migrants, Journal of Infection, 2024 (British Infection Association), section on cystic echinococcosis: investigations include serology (not invariably positive) with compatible ultrasound and MRI appearances, and cases should be discussed at a specialist hydatid MDT. https://www.journalofinfection.com/article/S0163-4453(24)00262-7/fulltext