Plasmodium knowlesi: Morphology

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Plasmodium knowlesi

Geographical distribution: Rarely seen, since it is acquired only from monkey host in forest or forest-fringe in S.E.Asia with no human to human spread. It is important to recognise this parasite however as travellers from affected areas may contract this species which has rapid division (each 24 hours) and may have high-parasitaemia with the potential for life threatening disease.

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The early trophozoite

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• File:PKET1.jpg

• Generally present and most resemble P.falciparum
• Small (1/3 to 1/2 of erythrocyte) relatively fine
• Occasionally non -vacuolated
• Double dots may be seen often at opposite poles
• Multiple infection is cells frequent, but accolé forms rare or absent
• No size change, stippling or pigment at this stage

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The late trophozoite

File:PKLT.jpg

• Usually present and most closely resemble P.malariae
• May be dense amoeboid or band-form, but generally retain a vacuole
• Acquiring pigment at late stages, may be separate or clumped
• Occasional sparse dots may seen (Sinton or Mulligan's stippling)
• Red cell size generally unaffected

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The schizont

leftt

• Present in mast cases partly resemble P.malariae
• Up to 16 merozoites (exceeds P.malariae)
• Do not generally fill the erythrocyte,.may be irregular or grape-like.
• Erythrocyte not enlarged may be a irregular.
• Dots are often seen.

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The gametocyte

File:PMG.jpg

• 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

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Gallery

Click here to see gallery of Plasmodium malariae forms

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