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 (rings) of Plasmodium falciparum are often thin and delicate, measuring on average 1/5 the diameter of the red blood cell.  Rings may possess one or two chromatin dots. They may be found on the periphery of the RBC (accolé, appliqué) and multiply-infected RBCs are not uncommon.  Ring forms may become compact or pleomorphic depending on the quality of the blood or if there is a delay in making smears.  There is usually no enlargement of infected RBCs.

Plasmodium falciparum ring stage

A

A: Ring-form trophozoites of P. falciparum.  Fig. 1: Normal red cell; Figs. 2-10: Increasingly mature ring stage parasites.
Illustration from: Coatney GR, Collins WE, Warren M, Contacos PG. The Primate Malarias. Bethesda: U.S. Department of Health, Education and Welfare; 1971.

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

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

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

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

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

F: Ring-form trophozoites of P. falciparum in a thin blood smear.
G: Ring-form trophozoites of P. falciparum in a thin blood smear.  Image courtesy of the Arizona State Public Health Laboratory.

Maurer's clefts in Plasmodium falciparum infection Maurer's clefts in Plasmodium falciparum infection
H I

H, I: Ring-form trophozoites in a thin blood smear, exhibiting Maurer's clefts.

 
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