Plasmodium malariae: Morphology

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Plasmodium malariae
P. malariae infection overlaps geographically with the distribution of P.falciparum in areas that include sub-Saharan Africa, Southeast Asia, Indonesia, the western Pacific and in areas of the Amazon Basin of South America.

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The early trophozoite

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During this later growth stage the rings enlarge and begin to modify the erythrocyte, forming typical features of the species.

• Small but well-formed rings are typically seen sometimes with a central chromatin dot or elongation
• Red cells are generally of normal size, though occasionally may have reduced volume
• Pigment will not generally be present at this developmental stage

GALLERY: P.malariae early trophozoites

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The late trophozoite

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In this species the parasite form changes significantly as the mature, characteristically elongating or becoming more angular, red cells may often appear smaller though not distorted.

• Parasites may be elongated, forming a band across the infected red cell
• Others spread to form an angular or basket form within the red cell
• Red cells remain round, but red cell size is often reduced
• cytoplasmic dots are uncommon but Ziemann's stippling may be seen
• Pigment can now be seen over the parasite surface

GALLERY: P.malariae late trophozoites

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The schizont

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Often present in the blood, these small schizont forms may have species-specific features.

• These are often seen in this species – the number of individual merozoites is often low (around 8)
• The central area of clumped pigment may have merozoites arranged to form a “daisy head” appearance
• At this stage the erythrocyte is devoid of haemoglobin and the small size is readily detected

GALLERY: P.malariae schizonts

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The gametocyte

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The sexual replication form in this species tend to be small, neat, and round.

• Gametocytes tend to be regular and round in shape.
• The parasites are small and do not generally fill the erythrocyte
• Haemoglobin is absent and scattered pigment overlies or surrounds the gametocyte

GALLERY: P.malariae gametocytes

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