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Biology of the schizont: Difference between revisions

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(Created page with "What is the schizont stage? Remember that following the trophozoites stage, malaria parasites may enter one of two separate pathways: (1) Sexual replication: male or female gametocyte are formed that are taken up by mosquitoes allowing the invasion of new hosts. (2) Asexual replication: schizonts are formed eventually forming individual merozoites that expand the infection by invading new red cells. ------------------------------------------------------------------------...")
 
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What is the schizont stage?
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Remember that following the trophozoites stage, malaria parasites may enter one of two separate pathways:
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(1) Sexual replication: male or female gametocyte are formed that are taken up by mosquitoes allowing the invasion of new hosts.
'''Navigation'''</br>
(2) Asexual replication: schizonts are formed eventually forming individual merozoites that expand the infection by invading new red cells.
<span style="font-size:90%">>[[Malaria_Index|Main Malaria Index]]''</span></br>
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<span style="font-size:90%">>>[[Malaria_Biology|Malaria Biology Index]]''</span></br>
This section will look at asexual replication: the schizonts and merozoites:
<span style="font-size:90%">>>>Current page: '''Schizont Biology'''</span>
 
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<span style="font-size:160%; color:navy">Biology of the Schizont</br></span>
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|colspan="1" style = "font-size:100%; color:black; background: white"|<span style="color:navy></span>
   
   
The stage begins with the first cycle of asexual replication forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.
The stage begins with the first cycle of '''asexual replication''' forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.
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The stage has specific features that have clinical and diagnostic relevance:
<gallery mode="nolines" widths=300px heights=300px>
File:the schizont.jpg|<span style="font-size:80%">''Formation and release of merozoites''</span>|link={{filepath:the schizont.jpg}}
The stage begins with the first cycle of asexual division producing two chromatin masses (1), this is followed by further cycles of replication that in this case result in the formation of 8 daughter parasites (2&3). These daughter parasites mature and are then released into blood as separate “merozoites” (4&5). These very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).
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Morphological relevence
 
1. The number of replication cycles differs between species.
(1) The stage begins with the first cycle of asexual division producing two chromatin masses</br>
Some species undergo more cycles of replication, this means the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax).
(2) This is followed by further cycles of replication </br>
2. This stage may not always take place in blood.
(3) In this case this results in the formation of 8 daughter parasites </br>
In P.falciparum the schizont form adheres within the small vessels so is not seen in blood unless infection is very severe
(4) The daughter parasites mature and the red cell ruptures to release the “merozoites” </br>
(5) The released merozoites very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).
 
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{| class="wikitable" style="border-style: none; border-width: 2px; border-color: gainsboro; color:black"
|colspan="1" style = "font-size:100%; color:black; background: gainsboro|'''Morphological features and relevance'''
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(1) '''The number of replication cycles differs between species:''' the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax)</br>
(2) '''This stage may not always occur in blood:''' schizonts of ''P.falciparum'' adhere within the small vessels so is not seen in blood unless infection is very severe
</br></br>
 
<gallery mode="nolines" widths="200px" heights="220px" >
File:Schizontreal4.jpg|Mature schizont releasing merozoites|link={{filepath:Schizontreal4.jpg}}
</gallery>
 
<span style="font-size:10%"></span> The progressive maturation of this parasite stage means that they have a wide range of morphological forms. However, these can be readily recognised on blood films by reference to their biology
 
[ [[Images of schizont morphology|See clinical images illustrating schizont development]] ]
 
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{| class="wikitable" style="border-style: none; border-width: 2px; border-color: gainsboro; color:black"
|colspan="1" style = "font-size:100%; color:black; background: gainsboro |'''Relevance of schizonts to clinical biology'''
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Morphology of schizonts (link)
The release of merozoites from schizonts exposes the body to large amounts of free parasite antigens no longer contained within the erythrocytes - the result is an immune response causing high fever and illness symptoms. In some cases the development of parasites is synchronous so that all schizonts mature and release their merozoites at the same time - although rarely seen now, this pattern of development may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.


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Relevance of schizonts to disease symptoms
Development of parasites may be synchronous so that all schizonts mature and release their merozoites at the same time. The release of merozoites exposes the body to large amounts of free parasite antigens at that point in time. The result is a high fever and illness which may settle afterwards. Although rarely seen now, this may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.

Latest revision as of 18:02, 6 November 2024

Navigation
>Main Malaria Index
 >>Malaria Biology Index
 >>>Current page: Schizont Biology

Biology of the Schizont


The stage begins with the first cycle of asexual replication forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.

  • Formation and release of merozoites

    Formation and release of merozoites


(1) The stage begins with the first cycle of asexual division producing two chromatin masses
(2) This is followed by further cycles of replication
(3) In this case this results in the formation of 8 daughter parasites
(4) The daughter parasites mature and the red cell ruptures to release the “merozoites”
(5) The released merozoites very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).

Morphological features and relevance


(1) The number of replication cycles differs between species: the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax)
(2) This stage may not always occur in blood: schizonts of P.falciparum adhere within the small vessels so is not seen in blood unless infection is very severe

  • Mature schizont releasing merozoites

    Mature schizont releasing merozoites

The progressive maturation of this parasite stage means that they have a wide range of morphological forms. However, these can be readily recognised on blood films by reference to their biology

[ See clinical images illustrating schizont development ]

Relevance of schizonts to clinical biology


The release of merozoites from schizonts exposes the body to large amounts of free parasite antigens no longer contained within the erythrocytes - the result is an immune response causing high fever and illness symptoms. In some cases the development of parasites is synchronous so that all schizonts mature and release their merozoites at the same time - although rarely seen now, this pattern of development may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.

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