Plasmodium species
Plasmodium falciparum, early trophozoites with Maurer's clefts, thin blood film
Early trophozoites (ring forms) are the most commonly seen stage of Plasmodium falciparum in peripheral blood films. Less commonly, gametocytes are also seen. The ring forms of P. falciparum are thin and delicate, being less than 1/3 of the diameter of the infected red blood cells, and commonly take on applique forms and "head-phone" forms. The size of the infected cells are the same as the surrounding uninfected cells. Rarely, Maurer's clefts may be seen; they are relatively large red 'comma-shaped' inclusions. In comparison to Schuffner's dots (which may be seen in red blood cells infected with Plasmodium vivax and Plasmodium ovale), they are larger and fewer.
Plasmodium falciparum, early trophozoites, thick blood film
Early trophozoites (ring forms) are the most commonly seen stage of Plasmodium falciparum in peripheral blood films. Less commonly, gametocytes are also seen. The ring forms of P. falciparum are thin and delicate, and may occasionally have a double chromatin dot (producing the so-called 'head-phone' forms). Since this is a thick blood film, the red blood cells have been lysed and therefore, the size of the ring forms in comparison to the size of the red blood cells cannot be appreciated.
Plasmodium falciparum, early trophozoites, thin blood film
Early trophozoites (ring forms) are the most commonly seen stage of Plasmodium falciparum in peripheral blood films. Less commonly, gametocytes are also seen. The ring forms of P. falciparum are thin and delicate, being less than 1/3 of the diameter of the infected red blood cells, and commonly take on applique forms and "head-phone" forms. The size of the infected cells are the same as the surrounding uninfected cells. Rarely, Maurer's clefts may be seen, but are not present in the images here.
Plasmodium falciparum, gametocytes, effect of prolonged storage in EDTA
Although EDTA is the preferred anticoagulant for blood collected for malaria diagnosis, it still can have a detrimental effect on parasite morphology overtime. In this case, the crescent-shaped gametocytes of Plasmodium falciparum began to round up after several days of storage in EDTA, thus leading to a potential mis-identification of a mixed infection.
Plasmodium falciparum, gametocytes, thin blood film
Shown here are the classic crescent or 'banana-shaped' gametocytes of Plasmodium falciparum. The gametocytes are intracellular, even though they can sometimes appear to be extracellular.
Plasmodium malariae, early trophozoites, thin blood film
The early trophozoites (ring forms) of Plasmodium malariae have a similar appearance to the rings of P. falciparum but are slightly thicker and bigger. Occasionally, the chromatin dot of the P. malariae ring appears to be detached within the center of the ring, giving the so-called "bird's eye" form. The size of the infected red blood cell is the same or smaller than the size of the surrounding red blood cells.
Plasmodium malariae, late trophozoites, thin blood film
As the trophozoites of Plasmodium malariae mature, they may form characteristics "band" or "basket" forms. The size of the infected red blood cell is the same or smaller compared to the size of the surrounding red blood cells.
Plasmodium malariae, mature schizonts, thin blood film
Mature schizonts of Plasmodium malariae have 6 to 12 merozoites that are classically (but not always) arranged around a central clump of coarse brown hemozoin pigment. This arrangement is called a 'rosette' or 'daisy head'.
Plasmodium ovale, late trophozoites, thin blood film
It can sometimes be difficult to differentiate infection with Plasmodium ovale from infection with Plasmodium vivax on Giemsa-stained thin films since both infect younger red blood cells (so that infected cells are slightly larger than uninfected red blood cells) and produce Schuffner's stippling. However, a number of useful features exist for differentiating the two species; for example, approximately 1/3 of cells infected with P. ovale take on an oval shape (hence the name 'ovale'), and the late-stage trophozoites of P. ovale tend to be more compact when compared to the ameboid forms of P. vivax. Also, cells infected with P. ovale commonly have jagged or 'fimbriated' contours. Additional features that can also be considered are the color/consistency of the hemazoin pigment, deformability of the erythrocyte membrane, and number of merozoites in the mature schizonts.
Plasmodium vivax, gametocytes, thin blood film
The gametocytes of P. vivax are round-to-oval and fill the cytoplasm of the infected red blood cells. Stippling (Schuffner's dots) is commonly present when stained at the appropriate pH (7.2). Plasmodium vivax may be difficult to tell apart from Plasmodium ovale when only examining a few cells like those shown here. Therefore, it is important to examine multiple infected cells and carefully note the different diagnostic features.
Plasmodium vivax, late trophozoites, thin blood film
It can sometimes be difficult to differentiate infection with Plasmodium ovale from infection with Plasmodium vivax on Giemsa-stained thin films since both infect younger red blood cells (so that infected cells are slightly larger than uninfected red blood cells) and produce Schuffner's stippling. However, a number of useful features exist for differentiating the two species; for example, cells infected with P. vivax are more deformable and often mold to the contours of the surrounding cells. Also, the late-stage trophozoites of P. vivax tend to be more ameboid when compared to the compact forms of P. ovale.
Plasmodium vivax, schizonts, thin blood film
Mature schizonts of Plasmodium vivax have 12 to 24 merozoites. Like most other forms of this parasite, the infected red blood cell is enlarged and Schuffner's dots may be seen.
