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<span style="font-size:130%; color:black">'''Morphology of ''Plasmodium falciparum'' '''</br></span><span style="font-size:90%">(See Malaria Biology pages for an explanation of these stages)</span>
 
<span style="font-size:110%; color:black">''' ''Plasmodium vivax'' '''</br></span><span style="font-size:90%"></span>
 
<span style="font-size:90%; color:black">''P.vivax'' is considered a parasite of Central and South America, India and S.E.Asia. The low frequency of the Duffy antigen (that facilitates the entry of ''P.vivax'' into erythrocytes) means that this species has lower frequency in Africa. Aside from this however ''Plasmodium vivax'' infection occurs across the widest geographic area of all the human malarias, extending well into temperate climates. This behaviour is enabled by the dormant stage in the human liver, where the parasite can "rest", allowing it to survive mosquito-free cold seasons when transmission and propagation in the mosquito-host is not possible.</span>  
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</br><span style="font-size:130%">The early trophozoite</span></br>
</br><span style="font-size:110%">The early trophozoite</span></br>
<gallery mode="nolines" widths=250px heights=250px>
<gallery mode="nolines" widths=220px heights=220px>
File:PFETc.jpg|link={{filepath:PFETc.jpg}}
File:PVETanno.jpg|link={{filepath:PVETanno.jpg}}
File:PFET3g.jpg|link={{filepath:PFET3g.jpg}}
File:PVET3.jpg|link={{filepath:PVET3.jpg}}
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</gallery>
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The earliest growth stage, this is characterised by fine ring forms with few other changes to red cell or parasite.
<span style="font-size:90%">The earliest ring forms in this species may be indistinguishable from other species, but during the early trophozoite stage the parasite begins to aquire a more irregular forms and to modify the erythrocyte and added dots, altered size and shape begin to be present.</span>
 
 
*[[Ring forms]] are fine and delicate and may be the sole form present ([[Synchronous parasite development|synchronicity]])
*<span style="font-size:90%">Erythrocytes begin to show increased [[Red cell size and shape main 2|cell size]]
*Frequently the red cells contain [[multiple parasites]]  
*<span style="font-size:90%">Parasites retain a ring form but may aquire a more irregular form  
*Parasites may have a distinctive [[Double chromatin dot forms|"double dot"]] or signet ring form
*<span style="font-size:90%">Parasites are generally large - occupying up to half of the erythrocyte
*Parasites may appear on the [[Accolé form|accolé forms]] that appear flattened against the cell membrane
*<span style="font-size:90%">Cytoplasmic [[Added dots main PV|Schüffner's dots]] may appear at this stage, although pigment is less uncommon
*Affected red cells have normal size and haemoglobin content
</br>
</br>
<div style="width: 350px">
'''GALLERY:'''
{| class="wikitable" style="border-left:solid 4px navy;border-right:solid 4px navy;border-top:solid 4px navy;border-bottom:solid 4px navy; font-size:110%; color:navy; align:center"
[[P.vivax early trophozoites gallery|''P.vivax'' early trophozoites]]
| colspan="1"''|[[P.falciparum early trophozoites gallery|GALLERY]]''
|}
</div>
 
 
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</br><span style="font-size:110%">'''The late trophozoite'''</span>
</br><span style="font-size:130%">The late trophozoite</span>
<gallery mode="nolines" widths=220px heights=220px>
<gallery mode="nolines" widths=250px heights=250px>
File:PVLTanno.jpg|link={{filepath:PVLTanno.jpg}}
File:PFLTc.jpg|link={{filepath:PFLTc.jpg}}
File:PVLT1.jpg|link={{filepath:PVLT1p.jpg}}
File:PFLT1p.jpg|link={{filepath:PFLT1p.jpg}}
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The later growth stage of trophozoites where parasites modification of the erythrocyte is seen with characteristic added dots and possible minor changes to red cell form:
<span style="font-size:90%">The later growth stage during which parasites grow considerably and lose their ring appearance aquiring more irregular and complex shapes. This process is accompanied by substantial modification of the red cell and metabolism of haemoglobin to form malaria pigment.</span>
   
   
*Parasites resemble early ring forms, but are thicker and may be slightly larger
*<span style="font-size:90%">Infected erythrocytes become significantly enlarged and irregular in shape
*Additional blue/grey dots and clefts are seen in red cell cytoplasm when [[stained correctly]]  
*<span style="font-size:90%">Parasites lose their ring appearance becoming irregular and "[[Amoeboid_form_main|amoeboid]]" in form
*These dots have low number a characteristic "dot" or "line" form [[Added dots main|Maurer's dots and clefts]]
*<span style="font-size:90%">Numerous red/purple Schüffner's dots are present in the cytoplasm of red cells  
*[[Red cell size and shape main|Size and shape]] of infected red cells is usually unaffected, but may become crenated
*<span style="font-size:90%">[[Malaria pigment pv|malaria pigment]] is often present and has an irregular distribution
*The [[Double chromatin dot forms|double dot]], [[Accolé form| accolé]], and [[multiple parasites|multiple parasite]] forms remain present
</br>
</br>
<div style="width: 350px">
'''GALLERY:'''
{| class="wikitable" style="border-left:solid 4px navy;border-right:solid 4px navy;border-top:solid 4px navy;border-bottom:solid 4px navy; font-size:110%; color:navy; align:center"
[[P.vivax late trophozoites gallery|''P.vivax'' late trophozoites]]
| colspan="1"''|[[P.falciparum late trophozoites gallery|GALLERY]]''
|}
</div>
 
 
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</br><span style="font-size:110%">'''The schizont'''</span></br>
</br><span style="font-size:130%">The schizont</span></br>
<gallery mode="nolines" widths=250px heights=250px>
<gallery mode="nolines" widths=250px heights=250px>
File:PFSc.jpg|link={{filepath:PFSc.jpg}}
File:PVSanno.jpg|link={{filepath:PVSanno.jpg}}
File:PFS1p.jpg|link={{filepath:PFS1p.jpg}}
File:PVS3.jpg|link={{filepath:PVS3.jpg}}
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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'':
The asexual stage of malaria parasite development - only some trophozoites form schizonts, but those that do undergo successive cycles of replication within the red cell to generate multiple [[Schizont_development_main|"merozoites"]] that then each invade a new red cell to continue and increase the infection.
 
*'''Do not generally circulate in this species unless overwhelming infection'''
*The merozoites cluster "untidily" but may be numerous (8-16+ when mature)
*In this species the loose [[Malaria pigment main|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
 
 
<div style="width: 350px">
{| class="wikitable" style="border-left:solid 4px navy;border-right:solid 4px navy;border-top:solid 4px navy;border-bottom:solid 4px navy; font-size:110%; color:navy; align:center"
| colspan="1"''|[[P.falciparum schizont gallery|GALLERY]]''
|}
</div>
 


*a range of maturing schizonts will generally be present within enlarged red cells
*when mature schizonts may contain 16-24 separate merozoites
*Schüffner's dots can be detected in any residual cytoplasm of the erythrocyte
*Malaria pigment is visible in irregularly distributed clumps over the schizont surface
</br>
'''GALLERY:'''
[[P.vivax schizont gallery|''P.vivax'' schizonts]]
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</br><span style="font-size:110%">'''The gametocyte'''</span></br>
</br><span style="font-size:130%">The gametocyte</span></br>
<gallery mode="nolines" widths=250px heights=250px>
<gallery mode="nolines" widths=250px heights=250px>
File:PFGc.jpg|link={{filepath:PFGc.jpg}}
File:PVGanno.jpg|link={{filepath:PVGanno.jpg}}
File:PFG1.jpg|link={{filepath:PFG1.jpg}}
File:PVG1.jpg|link={{filepath:PVG1.jpg}}
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The [[Macro_&_microgametocytes_PV|macrogametocyte and microgametocyte]] sexual replication form are similar to ''P.ovale''


The sexual replication in ''P.falciparum'' is very distinctive and may be the only form visible (particularly of after treatment).
*red cells are very large and may have round, ovoid or distorted forms
 
*macrogametocytes (female form) will often entirely fill the erythrocyte
*male and femaie gametocytes have the appearance of rods although these may be distorted
*microgametocytes (male form) have a cytoplasmic rim with visible Schüffner's dots
*The rod shapes may become curved by the red cell membrane to give the characteristic [[Banana gametocyte main|"banana" form]]”
*Malaria pigment is clumped evenly over the surface of the gametocyte
*The residual membrane (empty of haemoglobin) is often seen as a "blister" to one or both sides of the parasite
</br>
*The single chromatin area is in the centre of the parasite, often has [[Malaria pigment main|pigment]] overlying it
'''GALLERY:'''
 
[[P.vivax gametocyte gallery|''P.vivax'' gametocytes]]
 
<div style="width: 350px">
{| class="wikitable" style="border-left:solid 4px navy;border-right:solid 4px navy;border-top:solid 4px navy;border-bottom:solid 4px navy; font-size:110%; color:navy; align:center"
| colspan="1"''|[[P.falciparum gametocyte gallery|GALLERY]]''
|}
</div>
 
 
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Latest revision as of 18:41, 5 February 2025

Navigation
>Main malaria Index
>Main Species identification page

Plasmodium vivax

P.vivax is considered a parasite of Central and South America, India and S.E.Asia. The low frequency of the Duffy antigen (that facilitates the entry of P.vivax into erythrocytes) means that this species has lower frequency in Africa. Aside from this however Plasmodium vivax infection occurs across the widest geographic area of all the human malarias, extending well into temperate climates. This behaviour is enabled by the dormant stage in the human liver, where the parasite can "rest", allowing it to survive mosquito-free cold seasons when transmission and propagation in the mosquito-host is not possible.


The early trophozoite


The earliest ring forms in this species may be indistinguishable from other species, but during the early trophozoite stage the parasite begins to aquire a more irregular forms and to modify the erythrocyte and added dots, altered size and shape begin to be present.

  • Erythrocytes begin to show increased cell size
  • 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


GALLERY: P.vivax early trophozoites


The late trophozoite


The later growth stage during which parasites grow considerably and lose their ring appearance aquiring more irregular and complex shapes. This process is accompanied by substantial modification of the red cell and metabolism of haemoglobin to form malaria pigment.

  • Infected erythrocytes become significantly enlarged and irregular in shape
  • Parasites lose their ring appearance becoming irregular and "amoeboid" in form
  • Numerous red/purple Schüffner's dots are present in the cytoplasm of red cells
  • malaria pigment is often present and has an irregular distribution


GALLERY: P.vivax late trophozoites


The schizont


The asexual stage of malaria parasite development - only some trophozoites form schizonts, but those that do undergo successive cycles of replication within the red cell to generate multiple "merozoites" that then each invade a new red cell to continue and increase the infection.

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


GALLERY: P.vivax schizonts


The gametocyte


The macrogametocyte and microgametocyte sexual replication form are similar to P.ovale

  • red cells are very large and may have round, ovoid or distorted forms
  • macrogametocytes (female form) will often entirely fill the erythrocyte
  • microgametocytes (male form) have a cytoplasmic rim with visible Schüffner's dots
  • Malaria pigment is clumped evenly over the surface of the gametocyte


GALLERY: P.vivax gametocytes

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