Diagnostic Features of Plasmodium Species in Blood Smears
Characteristic | Plasmodium vivax* | Plasmodium falciparum | Plasmodium malariae† |
|---|---|---|---|
Infected red blood cells (RBCs) enlarged | Yes | No | No |
Schüffner dots‡ | Yes | No | No |
Maurer dots or clefts | No | Yes§ | No |
Multiple infections in RBCs | Rare | Yes | No |
Rings with 2 chromatin dots | Rare | Frequent | No |
Crescentic gametocytes | No | Yes | No |
Bayonet or band trophozoites | No | No | Yes |
Schizonts present in peripheral blood | Yes | Rare | Yes |
Number of merozoites per schizont (mean [range]) | 16 (12–24) | 12 (8–24)¶ | 8 (6–12) |
* Red blood cells (RBCs) infected with P. ovale are fimbriated, oval, and slightly enlarged; the parasites otherwise resemble P. vivax. | |||
† P. knowlesi is morphologically similar to P. malaria and has been confused with it. P. knowlesi should be considered in patients with malaria acquired in Southeast Asia, particularly in Malaysia. | |||
‡ Schüffner dots are best seen when the blood smear is stained with Giemsa stain. | |||
§ This feature is not always visible. | |||
¶ Schizonts are trapped in viscera and usually are not present in peripheral blood. | |||