Plasmodium vivax structure and life cycle

for UG & PG students

1. PLASMODIUM VIVAX
Complete Life Cycle

2. 40%oftheworld’spopulationlivesin
endemicareas
3-500millionclinicalcasesperyear
1.5-2.7milliondeaths(90%Africa)
increasingproblem(re-emerging
disease)
•resurgenceinsomeareas
•drugresistance(mortality)
•causativeagent=Plasmodiumspecies
•protozoanparasite
•memberofApicomplexa
•4speciesinfectinghumans
transmittedbyanopholinemosquitoes
•P. falciparum
•P. vivax
•P. malariae
•P. ovale

3. Itisminute,slightlycurved,sickle
shaped,uninucleatedorganism11to12
Ulengthand0.5to1uinwidth.
Motile,vibratorymovement,itis
coveredwithfirm,elastic,thincuticle
calledpellicle.
Bodyiselongatedslightlyswollenin
thecentreandtaperingtowardsthe
bothends.
Accessoryorganelles.
Structure of Sporozoite of P. vivax
Fig 1: Structure of Sporozoite of P. vivax

4. BirdandBacker(1963).
Pelliclewith3layerscontaininglongitudinally
arrangedcontractilemicrotubulesarein11.
Responsibleforwrigglingmovementofthebody.
AnteriorCuplikedepressioncalledapicalcap
having3contractilering.
Apairoflongnarrow,secretary,organellesopen
intoapicalcap.
Theysecretsproteolyticenzymeswhichfacilitate
entryofsporozoitesintolivercell
Manyconvolutedtubulesarepresentbut
unknownfunction
Micropylecontainthemalarialparasites
containingorganelles

7. Life Cycle
sporozoites injected during mosquito
feeding
invade liver cells
exoerythrocytic schizogony (merozoites)
merozoites invade RBCs
repeated erythrocytic schizogony cycles
gametocytes infective for mosquito
fusion of gametes in gut
sporogony on gut wall in hemocoel
sporozoites invade salivary glands
Transmission
sporozoites injected with saliva
enter circulation
trapped by liver (receptor-ligand)
Female Anopheles mosquito

8. Exoerythrocytic Schizogony
•hepatocyte invasion
•asexual replication
•6-15 days
•1000-10,000 merozoites
•no overt pathology

9. Erythrocytic Stage
•intracellularparasiteundergoestrophicphase
•youngtrophozoitecalled‘ringform’
•ingestshosthemoglobin
•cytostome
•foodvacuole
•hemozoin(malarialpigment)
•nucleardivision=beginschizontstage
•6-40nuclei
•buddingmerozoites=segmenter
•erythrocyterupturereleasesmerozoites
•bloodstageresultsindiseasesymptoms

10. Gametocytogenesis
•alternativetoasexualreplication
•inductionfactorsnotknown
•ringgametocyte
•sexualdimorphism
•microgametocytes
•macrogametocytes
•nopathology
•infectivestageformosquito
•occursinmosquitogut
•exposuretoairinduces
•gametoctyeactivatingfactorinmosquito

11. Sporogony
occursinmosquito(9-21d)
fusionofmicro-andmacrogametes
zygoteookinete(~24hr)
ookinetetransversesgutepithelium('trans-invasion’)
ookineteoocyst
betweenepitheliumandbasallamina
asexualreplicationsporozoites
sporozoitesreleased
sporozoitesmigratethroughhemocoel
sporozoites'invade'salivaryglands