Plasmodium vivax infections are usually characterised by the presence of more than one developmental stage in the peripheral blood film. The parasites parasitise enlarged erythrocytes which all contain Schuffner's dots.

 Trophozoites

Most trophozoites of P. vivax are already several hours old when they appear in peripheral blood and by that time the Schuffners dots are already visible. The trophozoites are actively amoeboid and contain single or sometimes double chromatin dots that are either circular or ovoid. As the trophozoites mature, the Schuffner's dots increase in number and size and the parasite changes from large irregular rings to rounded or ovoid forms in mature trophozoites.

An early trophozoite of Plasmodium vivax showing hazy Schuffners dots

Red blood cell with multiple trophozoites of Plasmodium vivax.

A trophozoite of Plasmodium vivax showing amoeboid morphology

Gametocytes

Mature female gametocytes are large rounded parasites which fill or nearly fill the host cell. The cytoplasm is blue and fairly homogenous. The nuclear chromatin is a single, well defined purplish mass, varied in form and usually peripheral in distribution. Mature male gametocytes can be distinguished from females by the large, loose and ill defined mass of chromatin and by their paler colour and smaller mass.

A gametocyte of Plasmodium vivax

Schizonts

the parasitised red cell are much enlarged containing Schuffner's dots. The parasites large, filling the enlarged red cell. There are between 12-24 merozoites in the schizonts, usually16. The pigment is a golden brown central loose mass.

A Schizont of Plasmodium vivax