Vivax malaria relapse prevention — DTM&H MCQ

Correct answer: E — Primaquine radical cure

Primaquine radical cure (E) is correct because Plasmodium vivax forms dormant hepatic hypnozoites that chloroquine (or any blood-stage drug) cannot clear, and with a confirmed normal quantitative G6PD result there is no contraindication to giving the 8-aminoquinoline. UK treatment guidelines state that dormant parasites persist in the liver after treatment of P. vivax or P. ovale infection, and that the only currently effective drug for eradication of hypnozoites is primaquine, ideally overlapped with the blood-stage schizonticide to boost efficacy. Without radical cure, relapse from liver-stage reactivation is common even after successful clearance of the acute blood-stage infection. The normal G6PD assay is the key permissive finding that unlocks this step in her management. Why the other options are wrong: C. Mefloquine weekly dosing: this is a chemoprophylactic regimen, not a treatment for established infection, and does not address hypnozoites at all. B. Ivermectin community dosing: this is an antiparasitic used for strongyloidiasis or mass drug administration for other helminths/ectoparasites; it has no antimalarial or hypnozoiticidal activity. A. Artesunate second course: she has already responded clinically to chloroquine, so there is no indication of treatment failure or severe malaria requiring artesunate; artesunate also has no activity against liver-stage hypnozoites. D. Doxycycline completion: doxycycline is used for chemoprophylaxis or as an adjunct in falciparum treatment, not for radical cure of vivax hypnozoites, and it has no hypnozoiticidal effect. Key point: after blood-stage clearance of P. vivax (or P. ovale), radical cure with primaquine is mandatory once G6PD deficiency has been excluded, otherwise relapse from persistent liver hypnozoites is likely.

Reference: UK malaria treatment guidelines 2016, Journal of Infection (British Infection Association), Points 20 to 22 on radical cure with primaquine and G6PD testing, https://www.journalofinfection.com/article/S0163-4453(16)00047-5/fulltext