Comparative morphology of human and animal malaria parasites. I. Host-parasite interface.

Human and animal malaria parasites (Plasmodium falciparum, P. malariae, P. vivax, P. berghei, P. gallinaceum) were studied using special fixation and standardized methods, with special attention to their effects on host cells. Morphological alterations induced by the parasites in infected erythrocytes included knobs, invaginations, and caveola-vesicle complexes on the surface of the host cell and clefts, microvesicles, and small vesicles in the cytoplasm of the infected erythrocytes. For P. malariae, the ultrastructural study revealed invaginations with associated microvesicles, but knobs did not occur on the surface of infected erythrocytes. The development of invaginations and microvesicles in P. malariae-infected erythrocytes corresponded to the morphological alterations induced by P. vivax. A new hypothesis concerning the origin of Schüffner's dots is discussed.