Acute schistosomiasis — DTM&H MCQ

Correct answer: E — Treat acute schistosomiasis symptomatically and arrange praziquantel after maturation

The correct answer is E, treat acute schistosomiasis symptomatically and arrange praziquantel after maturation. This traveller has classic Katayama syndrome: fever, urticaria, wheeze and marked eosinophilia occurring 2 to 8 weeks after freshwater exposure in an endemic African lake. UK guidance notes that the combination of eosinophilia, fever and rash in this time window after African freshwater swimming justifies empirical management even though serology and stool or terminal urine microscopy may be negative at this stage of infection but are useful if positive. Praziquantel acts on adult worms, not migrating schistosomula or eggs, so giving it too early can worsen the immunological reaction without eradicating the parasite, hence symptomatic treatment (with corticosteroids/antihistamines as needed) now, followed by praziquantel once the worms have matured, is the correct sequence. Why the other options are wrong: A. Discharge because microscopy is negative: negative stool and urine microscopy do not exclude infection at 5 weeks, since eggs are not yet being produced or excreted in detectable numbers during the pre-patent phase; discharging risks missing a diagnosis that can progress to neuroschistosomiasis. B. Give ivermectin as definitive therapy: ivermectin has no activity against Schistosoma species and is used for strongyloidiasis and other nematode infections, not trematodes. C. Start rifampicin and clarithromycin: this combination has no role in schistosomiasis; it is used for mycobacterial or atypical infections, which are not suggested by this clinical picture. D. Give high-dose chloroquine: chloroquine is an antimalarial with no schistosomicidal activity, and malaria does not explain the urticaria and wheeze pattern typical of Katayama syndrome. Key point: In Katayama syndrome, egg-based tests are often falsely negative because the worms have not yet matured, so treatment is symptomatic first, with praziquantel deferred until adult worms have developed.

Reference: UK guidelines for the investigation and management of eosinophilia in returning travellers and migrants, Journal of Infection, 2024, ScienceDirect (S0163445324002627)