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Plasmodium falciparum: Ring Stage Parasites

Smears from patients:
Plasmodium falciparum rings have delicate cytoplasm and 1 or 2 small chromatin dots. Red blood cells (RBCs) that are infected are not enlarged; multiple infection of RBCs more common in P. falciparum than in other species. Occasional applique forms (rings appearing on the periphery of the RBC) can be present.

A B C
D E F


A, B, C: Multiply infected red blood cells with applique forms in thin blood smears.
D: Signet ring form.
E: Double chromatin dot.
F: A thick blood smear showing many ring forms of P. falciparum



Plasmodium falciparum: Trophozoites

Smears from patients:
Although rarely seen in peripheral blood smears, older, ring stage parasites are referred to as trophozoites. The cytoplasm of mature trophozoites tends to be thicker and more dense than in younger rings. As P. falciparum trophozoites grow and mature, they tend to retain their ring-like shape and sometimes trace amounts of yellow pigment can be seen within the cytoplasm. Growing trophozoites in P. falciparum can appear slightly amoeboid in shape.

A B C D


A: Applique trophozoite: Note the slight amoeboid appearance of the parasite.
B: A larger, more mature trophozoite and smaller, younger ring stage parasites in a thin blood smear.
C, D: More mature and compact trophozoites. Note the presence of pigment in C.



Plasmodium falciparum: Schizonts

Smears from patients:
Schizonts are seldom seen in peripheral blood. Mature schizonts have 8 to 24 small merozoites; dark pigment, clumped in one mass.

A B C D


A: Immature schizont in a thin blood smear. B: Mature schizont. C, D: Ruptured schizonts in a thin blood smear.


Plasmodium falciparum: Gametocytes

 
A B  
C D E


A, B, C, D: Gametocytes of P. falciparum in thin blood smears. Note the presence of a “Laveran’s bib”, which is not always visible.
E: Two gametocytes captured from a thick blood smear.

 

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