Plasmodium: Characteristic features and classification

  • Plasmodium is an intracellular blood parasite which causes a malarial fever.
  • Charles Laveran discovered this parasite in the RBCs of man.
  • Ronald Ross discovered the oocyst in the gut wall of mosquito and established malarial mosquito relationship.
  • Grassi described the digenetic life cycle of Plasmodium.
  • There are more than 90 species of Plasmodium known to man but only four species cause different types of malaria in man.
    1. Plasmodium vivax: It causes benign tertian fever which is recurrent in every alternate days.
    2. Plasmodium malariae: It causes quartan fever which is recurrent after every 72 hours (3 days).
    3. Plasmodium falciparum: It causes malignant fever and there is no regularity of the fever.
    4. Plasmodium ovale: It causes benign sub-tertian fever which is seen after every 48 hours (2 days).

Classification of Plasmodium:

Phylum: Apicomplexa

Class: Sporozoasida

Order: Eucoccidiorida

Family: Plasmodiidae

Genus: Plasmodium

Species: falciparum,  malariae,  ovale,  vivax

  • These parasites show an alternation of generation in which they change their hosts to complete their life cycle.
  • In human host, the parasite lives in the RBCs and the parenchyma cells of liver.
  • In mosquitoes, the parasite resides in the salivary glands after their development in the mosquito’s alimentary canal (the stomach wall).
  • Plasmodium produces pigments (typical of their infection) in the RBCs (erythrocytes) during their developmental stages and the pigments are visualized by light microscopy.
  • Structurally, Plasmodium is dimorphic, i.e. found in two stages; sporozoite and trophozoite


  • It is the asexual stage in the life cycle of the parasite.
  • It is the infective stage, with anterior apical cap.
  • It is sickle shaped and both the ends tapering or thin.
  • Body is covered with thin and resistant cuticle.
  • It is uninucleate with centric nucleus.
  • The pellicle of the cell consists of longitudinal contractile microtubules which help in gliding locomotion.


  • It is the feeding stage and is amoeboid shaped (irregular shape).
  • It is uninucleate with eccentric nucleus.
  • The body is covered with plasmalemma.
  • The cell consists of food vacuoles having haemozoin (a toxic product formed after the breakdown of hemoglobin).

Plasmodium: Characteristic features and classification