Biology of the schizont
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| The schizont pathway |
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.
Basic schiont development (coloured images)
| Merozoite release |
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 releasethe “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 ad 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
Click for images of schizont morphology
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.