Plasmodium falciparum: Morphology
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| The early trophozoite |
The earliest growth stage, and often the only form present in this species:
- Ring forms that are fine and delicate
- Frequently the red cells contain multiple parasites
- Parasites may have a distinctive double chromatin dot (signet ring form)
- Parasites may appear on the edge of the red cell and have a flattened appearance (accolé forms)
- Affected red cells have normal size and haemoglobin content
| The late trophozoite |
The later growth stage:
- Parasites resemble early ring forms, but are thicker and may be slightly larger
- Additional blue/grey dots and clefts are seen in cytoplasm when stained correctly
- These added dots have a characteristic appearance Maurer's dots and clefts
- Size and shape of infected red cells is usually unaffected, but red cells may become crenated
- Typical double chromatin dot, Accolé forms, and multiple parasites/cell remain present
| The schizont |
The asexual form:
- Do not generally circulate in this species unless overwhelming infection
- Contain multiple asexually formed developing parasites (most frequently 8-16)
- Development is progressive: first there are multiple chromatin dots, later a distinct nucleus and cytoplasm appears
- Loose pigment may be seen in clumps between the parasites
- Red cell size is generally unaffected but haemoglobin will largely be absent (metabolised by the parasites)
The gametocyte
| The gametocyte |
The sexual replication form (very distinctive).
- Gametocytes are elongated but are also restricted by the red cell membrane
- They appear as straight rods but frequently curve into a “banana form”
- The residual membrane (empty of haemoglobin) may appear as a "blister" to the side of the parasite
- The single chromatin area is in the centre of the parasite, often pigment overlies or surrounds it
- Gametocytes may not be seen in many cases.