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. ovale usually contain a single chromatin dot, but may contain double-chromatin dots.  Multiply-infected RBCs may be seen, making the rings difficult to differentiate from P. falciparum. The single rings may be difficult to differentiate from P. vivax, as the cytoplasm is usually thick with a large chromatin dot.  As the trophozoites mature, they are less amoeboid than P. vivax and may exhibit fimbriation and Schüffner's dots.  Infected RBCs are not usually enlarged as in P. vivax infections.

Plasmodium ovale ring-form trophozoites

A

A: Ring-form trophozoites of P. ovale in thin blood smears.  Fig. 1: Normal red cell; Figs. 2-5: Ring-form 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 ovale ring-form trophozoites in thick blood smear Plasmodium ovale ring-form trophozoites in thick blood smear
B C

B, C: Ring-form trophozoites of P. ovale in thick blood smears.

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

D, E: Ring-form trophozoites of P. ovale in thin blood smears.  Note the multiply-infected RBC in Figure D.

Plasmodium ovale ring-form trophozoites in thin blood smear
F

F: Ring-form trophozoites of P. ovale in a thin blood smear.  Note the multiply-infected RBC.

 
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