Plasmodium malariae: Morphology: Difference between revisions
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* | *Parasites are larger and may be elongated, sometimes forming a [[band]] across the infected red cell | ||
* | *Red cells remain round, but [[size is often reduced]] | ||
* | *cytoplasmic dots are uncommon but [[may be seen]] | ||
* | *[[Pigment]] can now be seen over the parasite surface | ||
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Revision as of 10:17, 18 December 2024
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Morphology of Plasmodium malariae
(see Malaria Biology pages for an explanation of these stages)
Geographical distribution: P. malariae infection overlaps that 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.
The early trophozoite
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 someimes 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
The late trophozoite
Text
- Parasites are larger and may be elongated, sometimes forming a band across the infected red cell
- Red cells remain round, but size is often reduced
- cytoplasmic dots are uncommon but may be seen
- Pigment can now be seen over the parasite surface
The schizont
The asexual schizont stage of development will often be identified in the blood of this species, while smaller than P.vivax, species-specific features may not be clearly seen.
- A range of "schizont forms" will generally be present within moderately enlarged red cells
- When mature schizonts may contain 16-24 separate merozoites
- James' dots may be detected in any residual cytoplasm of the erythrocyte
- Pigment will be visible in irregularly distributed clumps
The gametocyte
The sexual replication form resembles P.vivax although generally smaller with sme species-specific forms detectable.
- Red cells will generally enlarged and may have ovoid or fimbriated form
- Macrogametocytes (female form) will often entirely fill the erythrocyte
- Microgametocytes (male form) have a cytoplasmic rim with visible James' dots
- Pigment is clumped evenly over the surface of the gametocyte
- Parasites tend to be small, although less fine than for P.falciparum, the number of parasites in the blood is often low.
- Infected blood tends to include all the developmental stages, some of which have features that particularly define the species
- Red cell are rarely enlarged, and most frequently have reduced size – this is a fairly useful indication of the the presence of P.malariae
- In normally stained samples there will not be added dots or clefts, although in very heavily stained samples these may be detected (name).
Schizonts
- These are often seen in this species – the number of individual merozoites is often low (around 8)
- Mature schizonts may have a characteristic central area of clumped pigment with the merozoites arranged around this forming a “daisy head”
- At this stage the erythrocyte is devoid of haemoglobin and the small size is readily detected
Gametocytes
- Gametocytes tend to be regular and round in shape.
- The parasites are small and do not generally fill the erythrocyte
- Haemoglobin is absent and pigment overlies the gametocyte