Are Iron-Scavenging Parasites Protective against Malaria

    Department of Biology, University of Puerto Rico, San Juan, Puerto Rico
    Departments of Medicine and Microbiology, New York University School of Medicine, New York

    To the EditorNyakeriga et al. [1] showed that, in Kenyan children, anemia was associated with a reduction in the incidence of clinical malaria. We provide a hypothesis that is based on this finding.

    Malaria has been a strong selector of human genes, since inherited conditions such as sickle-cell trait, thalassemias, and glucose-6-phosphate dehydrogenase deficiency provide partial protection against malaria. Because erythrocytes are central to the life cycle of Plasmodium falciparum, chronic anemia may lower host susceptibility to infection. A protective effect of iron deficiency against malaria has been supported by studies of animals [2] and humans [1]. Iron-supplementation treatment of anemia increases the risk of P. vivax malaria [35].

    In contrast, anemia-inducing parasites, including particular helminths and nematodes [46], appear to offer a benefit against malaria to humans who are infected with these organisms and who live in regions in which malaria is endemic [7]. Bacteria that induce iron-deficiency anemia in humans also might confer resistance to malaria. Helicobacter pylori, a longtime colonizer of humans [8] that has been shown to cause iron-deficiency anemia [912], commonly colonizes human populations in tropical areas. One biological cost of infection with H. pylori, in exchange for a possible benefit in protection against malaria, might be a higher risk of peptic ulcer disease. Just as malaria may have shaped host responses to H. pylori [13], H. pylori may affect the severity of malaria in infected populations through its role in iron homeostasis.

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