Among other Apicomplexan infections, host HIF-1α has been shown to be essential for Toxoplasma gondii survival and growth in host cells cultured at physiological oxygen levels (3% O2) (Spear et al., 2006), and is also necessary for the maintenance of Leishmania amazonensis parasitemia in human macrophages in vitro (Degrossoli et al., 2007). This evidence concerns the gene HIF1A and parasitic infectious disease.