Infective Stages of the Parasites (with examples and descriptions)

Sporozoite of Malarial Parasite

Plasmodium Vivax (Malaria): Sporozoite
Sprozoites has special predilection towards the salivary glands, so their concentration reach maxium in salivary ducts. When an infected female anopheles mosquito bites a susceptible person,  a single bite is capable of transmitting infection.


Entamoeba histolytica (Causes-Amoebic dysentery): Mature Quadrinucleate Cyst

Mature Quadrinucleate Cyst of Entamoeba histolytica
Mature Quadrinucleate Cyst of Entamoeba histolytica

Mature quadrinucleate cysts are the infective forms of Entamoeba histolytica. When these cysts are swallowed along with the contaminated food and drink by susceptible person, they are capable of further development and can cause Amoebic dysentery, Amoebic liver abscess etc.

Leishmania donovani (Visceral Leishmaniasis or Kala-azar): Promastigote

Transmission of L. donovani from man to man is carried out by a certain species of sandfly of the Genera Phlebotomus and Lutzomyia.

During blood meal feamle sandflies inoculate promastigote forms (flagellates) of Leishmania, which reaches to reticuloendothelial system and later can cause Visceral Leishmaniasis (Kala-azar)

Promastigote form of Leishmania
Promastigote form of Leishmania

Hookworm (GI Parasite): Filariform larvae

In Hookworm hatched L3 is the infective stage, transmission to humans may be via skin penetration or sometimes by oral route

Other parasites and their infective stages are: 

  1. Ascaris Lumbricoides (GI parasite): Mature fertilized egg (which contains Rhabiditiform larvae inside)
  2. Wuchereria bancrofti (Filariasis): Third larval Stage (L3)

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