The early ring-form trophozoites (rings) of Plasmodium knowlesi are similar to P. falciparum, as rings may show double chromatin dots. Appliqué forms (rings on the periphery of the RBC) may appear, as well as rectangular rings harboring one or more accessory chromatin dots. Red blood cells may also be multiply-infected. When full-grown, the non-amoeboid rings may occupy half or more of the host RBC.
In developing schizonts, the nucleus continues to divide until there are up to 16 (average 10) merozoites. As the schizont matures, it fills the host RBC and the pigment collects into one or a few masses. In the mature schizont, the merozoites may appear ‘segmented’ and the pigment has collected into a single mass.
Images courtesy of the CDC.
