for UG & PG students

1. PLASMODIUM VIVAX
Complete Life Cycle

2.  40% of the world’s population lives in
endemic areas
 3-500 million clinical cases per year
 1.5-2.7 million deaths (90% Africa)
 increasing problem (re-emerging
disease)
• resurgence in some areas
• drug resistance ( mortality)
• causative agent = Plasmodium species
• protozoan parasite
• member of Apicomplexa
• 4 species infecting humans
 transmitted by anopholine mosquitoes
• P. falciparum
• P. vivax
• P. malariae
• P. ovale

3.  It is minute, slightly curved, sickle
shaped, uninucleated organism 11 to 12
U length and 0.5 to 1 u in width.
 Motile, vibratory movement, it is
covered with firm, elastic, thin cuticle
called pellicle.
 Body is elongated slightly swollen in
the centre and tapering towards the
both ends.
 Accessory organelles.
Structure of Sporozoite of P. vivax
Fig 1: Structure of Sporozoite of P. vivax

4.  Bird and Backer (1963).
 Pellicle with 3 layers containing longitudinally
arranged contractile microtubules are in 11.
 Responsible for wriggling movement of the body.
 Anterior Cup like depression called apical cap
having 3 contractile ring .
 A pair of long narrow, secretary, organelles open
into apical cap.
 They secrets proteolytic enzymes which facilitate
entry of sporozoites in to liver cell
 Many convoluted tubules are present but
unknown function
 Micropyle contain the malarial parasites
 containing organelles

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
• intracellular parasite undergoes trophic phase
• young trophozoite called ‘ring form’
• ingests host hemoglobin
• cytostome
• food vacuole
• hemozoin (malarial pigment)
• nuclear division = begin schizont stage
• 6-40 nuclei
• budding merozoites = segmenter
• erythrocyte rupture releases merozoites
• blood stage results in disease symptoms

10. Gametocytogenesis
• alternative to asexual replication
• induction factors not known
• ring  gametocyte
• sexual dimorphism
• microgametocytes
• macrogametocytes
• no pathology
• infective stage for mosquito
• occurs in mosquito gut
• exposure to air induces
• gametoctye activating factor in mosquito

11. Sporogony
 occurs in mosquito (9-21 d)
 fusion of micro- and macrogametes
 zygote  ookinete (~24 hr)
 ookinete transverses gut epithelium ('trans-invasion’)
 ookinete  oocyst
 between epithelium and basal lamina
 asexual replication  sporozoites
 sporozoites released
 sporozoites migrate through hemocoel
 sporozoites 'invade' salivary glands