Plasmodium falciparum: Morphology
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| The early trophozoite |
The earliest growth stage, and may be the only form seen in this species:
- Ring forms that are fine and delicate
- Frequently the red cells contain multiple parasites
- Parasites may have a distinctive "double dot" or signet ring form
- Parasites may appear on the accolé forms that appear flattened against the cell membrane
- 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 red cell cytoplasm when stained correctly
- These dots have low number a characteristic "dot" or "line" form Maurer's dots and clefts
- Size and shape of infected red cells is usually unaffected, but may become crenated
- double dot, accolé, and multiple parasite forms 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 restricted into typical shape by the red cell membrane
- They parasites are rod shaped but the membrane may cause them to curve into a “"banana" form”
- The residual membrane (empty of haemoglobin) is often seen as a "blister" to the side of the parasite
- The single chromatin area is in the centre of the parasite, often has pigment overlying it
- Gametocytes may not be be seen, or may be the only form present (particularly after treatment)