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Malaria Life Cycle

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Plasmodium vivax

Morphology

Relative age of infected RBCs                Only those that are young & immature

Appearance of infected RBCs                 Enlarged, distorted

Ring Form

Ring Form:

• Delicate cytoplasmic ring measuring 1/3 RBC diameter
• Single chromatin dot
• Ring surrounds a vacuole

Trophozoite

Trophozoite:

• Irregular ameboid appearance
• Ring remnants common
• Brown pigment

Schizont

Schizont:

Immature schizont

• Multiple chromatin bodies
• Brown pigment

Mature schizont

• 12 to 24 merozoites occupying majority of the red cells
• Merozoites surrounded by cytoplasmic material
• Brown pigment may be present

Gametocyte

Gametocyte:

  Microgametocyte

• Large pink to purple chromatin mass surrounded by colourless to pale halo
• Brown pigment common

  Macrogametocyte

• Round to oval cytoplasm
• Eccentric chromatin mass
• Delicate light-brown pigment present throughout cell

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Plasmodium ovale

Morphology

Relative age of infected RBCs                Only those that are young & immature

Appearance of infected RBCs                 Oval & enlarged, distorted with ragged
                                                          cell walls

Ring form:

• Resembles that of P. vivax
• Ring larger in size than P. vivax
• Ring often tick & somewhat ameboid in appearance

Ring Form

Trophozoite:

• Ring appearance usually maintained until late in development
• Ameboid tendencies not as evident as P. vivax

Trophozoite

Schizont:

Immature schizont

• Progressive dividing chromatin surrounded by cytoplasmic material, often maintains circular shape early in development

Mature schizont

• Parasites occupy three quarters of RBCs
• 8 to 12 merozoites maybe present
• Rosettes of an average of 8 merozoites

Schizont

Gametocyte:

• Similar to P. vivax, only smaller in size

Gametocyte

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Plasmodium malariae

Morphology

Relative age of infected RBCs                Only mature cells

Appearance of the infected RBCs           Normal size, no distortion

Ring Form

Ring form:

• Smaller in size than P. vivax
• Occupies 1/6 of the RBS
• Heavy chromatin dot
• Vacuole may appear “filled in”
• Pigment forms early

Trophozoite

Trophozoite:

• Non-ameboid solid cytoplasm that may assume a roundish, oval, band, or bar shape
• Cytoplasm contains coarse dark brown pigment that may mask chromatin material
• Vacuoles are absent in mature stages

Schizont

Schizont:

Immature schizont

• Similar to that of P. vivax, only smaller and may contain large & dark peripheral or central granules

Mature schizont

• 6 to 12 merozoites arranged in rosettes or irregular clusters
• Central arrangement of brown-green pigment may be visible

Gametocyte:

• Similar to P. vivax, only smaller in size & pigment is usually darker & more coarse
• Older forms assume an oval shape

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Plasmodium falciparum

Morphology

Relative age of infected RBCs                May infect cells of all ages

Appearance of infected RBCs                 Normal size, no distortion

Ring form:

• Circle configuration (one chromatin dot) or headphone configuration (two chromatin dots)
• Scanty cytoplasm & small vacuole
• Multiple rings common
• Accolé forms common

Ring Form

Trophozoite:

• “Heavy rings” common with fine pigment granules
• Mature forms only seen in severe infections

Trophozoite

Schizont:

Immature schizont

• Multiple chromatin bodies surrounded by cytoplasm
• Only detected in severe infection

Mature schizont

• 8 to 36 merozoites (average 24) in clusters arrangement
• only detected in severe infections

Schizont

Gametocyte:

Microgametocyte

• Sausage or crescent shape
• Dispersed central chromatin with nearby black pigment visible

Macrogametocyte

• Sausage or crescent shape
• Compact chromatin
• Black pigment visible

Gametocyte

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Plasmodium knowlesi

Morphology

Appearance of infected RBCs                 Normal size, no distortion

The appearance of P.knowlesi resembles those of P.falciparum

Ring form:
 

• Delicate cytoplasm
• 1 to 2 prominent chromatin dots
• Occasional appliqué (accolé) forms

Trophozoite:

• Compact cytoplasm
• Large chromatin
• Occasional band forms
• Coarse, dark-brown pigment

Schizont:

• Mature = up to 16 merozoites with large nuclei
• Clustered around mass of coarse, dark-brown pigment
• Occasional rosettes
• Mature merozoites appear segmented

Gametocyte:

• Round to oval
• Compact, may almost fill RBC
• Chromatin compact
• Eccentric (macrogametocyte)
• More diffuse (microgametocyte)
•  Scattered brown pigment

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