Vivax Malaria: Old Drug, New Uses?

More than 40 % of the world popula-tion is at risk for malaria caused by Plasmodium vivax [1]. Because this parasite rarely causes severe disease in travelers or populations in temperate climates, it has been regarded as a rela-tively benign infection. We now know that this is not the case; in the tropics, vivax malaria can be severe and fatal [2]. Moreover, P. vivax has a persistent liver stage that can cause relapses many months or even years after the initial infection, and these hypnozoites can only be eliminated by additional treat-ment with primaquine. Treatment to accomplish radical cure of these hyp-nozoites is complicated by several factors that continue to elude scientific resolution. Most important, the 14-day primaquine treatment for relapse is un-reliable, and patients with G6PD-deficiency are susceptible to primaquine toxicity and the additional risk of hae-molysis [3]. The complexity of the biology and treatment of P. vivax have discouraged research, and this relative paucity of studies means that the public health impact of vivax malaria has been seriously underappreciated. Until recently, chloroquine was gen-erally effective as treatment for clinical episodes of vivax, but chloroquine re-sistance is prevalent and increasing in Oceania, Indonesia, and Peru [4]. Sulfadoxine-pyrimethamine (Fansidar) has not been the recommended treat-ment for vivax, but outside of Africa, patients are frequently infected with both P. vivax and P. falciparum, so ex-tensive use of this agent to treat falci-parum malaria has also selected resistance to both sulfadoxine and py