Plasmodium ovale: Morphology: Difference between revisions
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During this later growth stage the rings enlarge and begin to modify the erythrocyte, forming typical features of the species. | <span style="font-size:90%">During this later growth stage the rings enlarge and begin to modify the erythrocyte, forming typical features of the species.</span> | ||
*Large and robust-appearing [[rings]], not usually multiply infected | *<span style="font-size:120%">Large and robust-appearing [[rings]], not usually multiply infected | ||
*Red cells may become enlarged and may be ovoid or have a [[fimbriated]] apearance | *<span style="font-size:120%">Red cells may become enlarged and may be ovoid or have a [[fimbriated]] apearance | ||
*[[James' dots]] (indistinguishable from Schuffner’s dots) often appear | *<span style="font-size:120%">[[James' dots]] (indistinguishable from Schuffner’s dots) often appear | ||
*Pigment will not generally be present at the early trophozoite stage | *<span style="font-size:120%">Pigment will not generally be present at the early trophozoite stage | ||
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Revision as of 20:26, 13 December 2024
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Morphology of Plasmodium ovale
(See Malaria Biology pages for an explanation of these stages)
The early trophozoite
During this later growth stage the rings enlarge and begin to modify the erythrocyte, forming typical features of the species.
- Large and robust-appearing rings, not usually multiply infected
- Red cells may become enlarged and may be ovoid or have a fimbriated apearance
- James' dots (indistinguishable from Schuffner’s dots) often appear
- Pigment will not generally be present at the early trophozoite stage
The late trophozoite
During this growth stage parasites grows but generally retain a ring shape, this process is accompanied by further modification of the red cell with ovoid and fimbriated features more common; metabolism of haemoglobin causes malaria pigment to form.
- Parasites become larger and thickened, but the ring form is generally retained
- Red cell enlargement is seen and distortion causing ovoid and fimbriated forms
- James’ dots will now be prominent in appropriately stained specimens
- Pigment will now be seen over the surface of the parasite
The schizont
The schizont is the asexual form of the malaria parasite that will circulate in blood in most species, but is an uncommon feature in P.falciparum:
- Do not generally circulate in this species consider causes
- The merozoites cluster "untidily" but may be numerous (8-16+ when mature)
- In this species the loose pigment may be seen in clumps between the parasites
- Red cell size is generally unaffected but red cells become pale as haemoglobin is metabolised by the parasites
The gametocyte
The sexual replication in P.falciparum is very distinctive and may be the only form visible (particularly of after treatment).
- male and femaie gametocytes have the appearance of rods although these may be distorted
- The rod shapes may become curved by the red cell membrane to give the characteristic "banana" form”
- The residual membrane (empty of haemoglobin) is often seen as a "blister" to one or both sides of the parasite
- The single chromatin area is in the centre of the parasite, often has pigment overlying it