Plasmodium vivax: Morphology

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The early trophozoite

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The earliest ring forms may be indistinguishable from other species, but during this stage the parasite tends to aquire a more irregular forms and to show signs of modification of the erythrocyte (added dots, and altered size and shape).

• erythrocytes begin to show increased size and altered shape
• parasites retain a ring form but may aquire a more irregular form
• parasites are generally large - occupying up to half of the erythrocyte
• cytoplasmic Schüffner's dots may appear at this stage, although pigment is less uncommon

Click for P.vivax early trophozoite gallery

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The late trophozoite

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• PFVT-main image.jpg

The later growth stage during which parasites grow considerably and lose their ring appearance, this process is accompanied by substantial modification of the red cell and metabolism of it's haemoglobin to form malaria pigment.

• infected erythrocytes become significantly enlarged and irregular in shape
• parasites lose their ring appearnace becoming irregular and "amoeboid" in form
• numerous red/purple Schuffners dots are predent in the cytoplasm of red cells
• malaria pigment is often present and has an irregular distribution

Click for P.falciparum late trophozoite gallery

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The schizont

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• PVS-main image 2.jpg

The asexual form:

• a range of maturing schizonts will generally be present within enlarged red cells
• mature schizonts generally contain 16-24 separate merozoites
• schu8c3bcffneru8e28099s dots can be detected in any residual cytoplasm of the erythrocyte
• pigment is visible in irregularly distributed clumps over the schizont surface

Click for P.falciparum schizont gallery

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The gametocyte

The gametocyte

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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)

Click for P.falciparum gametocyte gallery

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the gametocyte file pvg.jpg leftt 200px link filepath pvg.jpg *very large with ovoid or distorted forms *macrogametocytes female may entirely fill the erythrocyte *microgametocytes male may have a thin cytoplasmic rim with visible schu8c3bcffneru8e28099s dots *pigment is clumped over the surface of the gametocyte