Diagnostic Findings [Last Modified: ]
Malaria
[Plasmodium falciparum] [Plasmodium knowlesi] [Plasmodium malariae] [Plasmodium ovale] [Plasmodium vivax]
Causal Agent Life Cycle Geographic Distribution Clinical Features Laboratory Diagnosis Treatment

Ring-form trophozoites of P. vivax usually have a thick cytoplasm with a single, large chromatin dot.  Rings may be difficult to distinguish from those of P. ovale.  The cytoplasm becomes amoeboid and Schüffner's dots may appear as the trophozoites mature.  Infected RBCs are often larger than uninfected RBCs.  Multiply-infected RBCs are not uncommon.

Plasmodium vivax ring-form trophozoites

A

A: Ring-form trophozoites of P. falciparum.  Fig. 1: Normal red cell; Figs. 2-6: Ring stage parasites (young trophozoites).
Illustrations from: Coatney GR, Collins WE, Warren M, Contacos PG. The Primate Malarias. Bethesda: U.S. Department of Health, Education and Welfare; 1971.

Plasmodium vivax ring-form trophozoites in thick blood smear Plasmodium vivax ring-form trophozoites in thick blood smear
B C

B, C: Ring-form trophozoites in a thick blood smear.

Plasmodium vivax ring-form trophozoites in thin blood smear Plasmodium vivax ring-form trophozoites in thin blood smear
D E

D, E: Ring-form trophozoites of P. vivax in a thin blood smear.

Plasmodium vivax ring-form trophozoites in thin blood smear Plasmodium vivax ring-form trophozoites in thin blood smear
F G

F, G: Ring-form trophozoites of P. vivax in a thin blood smear.

 
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