Plasmodium knowlesi: Morphology
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Plasmodium knowlesi
Geographical distribution: Rarely, 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, since it has rapid division (each 24 hours), and may have high-parasitaemia with the potential for rapidly developing life threatening disease.
The early trophozoite
- 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
The late trophozoite
- 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
The schizont
- 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.
The gametocyte
- 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
Gallery
Click here to see gallery of Plasmodium malariae forms