Strongyloidiasis before immunosuppression — DTM&H MCQ

Correct answer: B — Ivermectin before immunosuppression

The correct answer is B, ivermectin before immunosuppression. This man has serological evidence of Strongyloides stercoralis infection with eosinophilia, a classic picture in someone born in an endemic area such as Cambodia where autoinfection can persist subclinically for decades. Corticosteroids suppress the eosinophilic and Th2 response that normally contains the autoinfective larval cycle, allowing massive larval proliferation, gut and lung penetration, and Strongyloides hyperinfection or disseminated disease with gram-negative sepsis and mortality exceeding 50 percent even when treated. Because stool microscopy is insensitive and this risk is predictable once serology is positive, presumptive treatment with ivermectin should be given and ideally completed before starting high-dose steroids, not delayed until confirmatory larvae are seen. This is the standard pre-emptive strategy recommended whenever corticosteroids are planned in a seropositive or epidemiologically at-risk patient. Why the other options are wrong: A. Metronidazole and a luminal agent: this combination treats amoebic or other protozoal gut infections such as Entamoeba histolytica, not a nematode like Strongyloides, and has no activity against the parasite. E. No therapy unless larvae are seen in stool: waiting for stool microscopy is unsafe because larval excretion is intermittent and sensitivity is low, so a negative stool does not exclude infection, and delaying treatment risks fatal hyperinfection once steroids start. C. Praziquantel before prednisolone: praziquantel is active against trematodes and cestodes (schistosomes, tapeworms) but has no efficacy against Strongyloides, an intestinal nematode. D. Albendazole after prednisolone is completed: albendazole is a less reliable alternative to ivermectin for Strongyloides and, critically, treating after steroids have already been started or completed is too late to prevent hyperinfection triggered by the immunosuppression. Key point: any patient from an endemic area who is Strongyloides seropositive or at epidemiological risk must receive ivermectin before, not after, corticosteroids or other immunosuppression to prevent fatal hyperinfection syndrome.

Reference: World Health Organization, A parasitic infection that can turn fatal with administration of corticosteroids, 17 December 2020, https://www.who.int/news/item/17-12-2020-a-parasitic-infection-that-can-turn-fatal-with-administration-of-corticosteroids