Ultrastructure of erythrocytes fromAotus trivirgatus andSaimiri sciureus monkeys infected byPlasmodium vivax

Abstract

Erythrocytes fromAotus andSaimiri monkeys parasitized byPlasmodium vivax show dramatic changes starting during the early stages of parasite, development. Invaginations of the erythrocyte membrane, caveolae, are found during all parasite development stages. Up to six vesicles can be fused with one caveola, forming a caveola-vesicle complex. As the parasite grows, large accumulations of these vesicles can be seen within the erythrocyte cytoplasm. In addition to these caveolaevesicle complexes, knob-like structures appear on the erythrocyte surface that are similar to those seen on the host-cell surface ofP. falciparum-infected red cells. Extensive membrane-bound clefts spread throughout the erythrocytic cytoplasm, sometimes forming stacks or large whorls. The density of the red cell cytoplasm begins to decrease at an early stage of parasite development. All of these changes may be responsible for an increased fragility of theP. vivax-infected, red cell fromAotus orSaimiri monkeys Moreover, the large amount of parasite material that is released during rupture of the red cell may account for the high fever paroxysms that are characteristic ofP. vivax malaria infection. pathology caused by the parasite on and within the host cell. As a new finding, knobs appearing on the infected erythrocyte surface are described.