Resistance to primaquine in Plasmodium gallinaceum, and the problem of resistance to quinoline compounds in malaria parasites

The shape and size of hemozoin crystals distinguishes diverse Plasmodium species

All Plasmodium species produce a brown birefringent crystal known as malarial pigment or hemozoin. This work compares the morphology of hemozoin from P. falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi, P. brasilianum, P. yoelii and P. gallinaceum. The human, primate and mouse hemozoins have a regular, flat-faced cuboidal morphology with modest size differences in contrast to the larger, regularly irregular barrel shape with a waffle surface of the avian, P. gallinaceum, pigment. Hydrogen peroxide (H2O2), as a biochemical test reagent, can distinguish the hemozoins by different concentrations to degrade half of the crystals. A surface area to volume ratio explains both the appearance and susceptibility to H2O2 degradation. The hemozoin from each species is able to be a template for hemozoin extension inhibitable by the quinolines. P. gallinaceum hemozoin more closely resembles the hemozoin from another avian apicomplexan, Haemoproteus, rather than the hemozoin from the mammalian malaria species. These distinct morphological characteristics between mammalian and avian crystals suggest different biochemical environments that affect morphology.