Relapsing Plasmodium vivax malaria — DTM&H MCQ

Correct answer: D — Relapsing Plasmodium vivax malaria

The correct answer is D, relapsing Plasmodium vivax malaria. The delayed presentation (7 months post travel), recurrent fevers, and thin film showing enlarged red cells with Schuffner dots and trophozoites are classic for P. vivax, which forms dormant liver hypnozoites capable of causing relapse long after the primary infection. Schuffner dots are a stippling artefact seen specifically in vivax and ovale infected erythrocytes, not falciparum, and enlarged host red cells reflect vivax's preference for reticulocytes. UK treatment guidance emphasises that hypnozoite reactivation, not treatment failure, explains this pattern, and that radical cure with primaquine after G6PD testing is required to prevent further relapses. Eritrea is a mixed falciparum/vivax endemic area, supporting vivax as the acquired species here. Why the other options are wrong: E. Recrudescent Plasmodium falciparum malaria: Falciparum does not form hypnozoites, so it cannot cause relapse months later; recrudescence reflects incompletely cleared blood-stage parasites, and falciparum-infected cells are not enlarged nor do they show Schuffner dots (Maurer's clefts instead). C. Acute dengue infection: Dengue does not produce blood film findings of parasitised red cells with Schuffner dots or trophozoites; it is a viral infection detected serologically or by NS1/PCR, not by thick/thin film microscopy. B. Babesiosis acquired in East Africa: Babesiosis is exceedingly rare in East Africa, and while it can show intraerythrocytic ring forms, it does not produce Schuffner dots, which are specific to vivax/ovale. A. Hyperreactive malarial splenomegaly: This is a chronic immunological syndrome with massive splenomegaly and high IgM, not recurrent febrile parasitaemia with visible trophozoites on film. Key point: Schuffner dots plus enlarged infected erythrocytes on film, with fever recurring months after travel, indicate P. vivax hypnozoite relapse, mandating primaquine radical cure after G6PD testing.

Reference: PHE Advisory Committee on Malaria Prevention (Lalloo DG et al), UK malaria treatment guidelines 2016, Journal of Infection 2016;72(6):635-649