Trypanosoma cruzi || Parasitic Life Cycle in Human Host
Trypanosoma cruzi passes its life cycle in two host;
1. Human
2. Vector reduviid bugs, also known as kissing bugs
This video shows the life cycle of trypanosoma cruzi in human host.
Metacyclic trypomastigote form is infective to human, that is found in feces of insect reduviid bug.
reduviid bugs are nocturnal in habitat.
Human gets infection while insect bite by reduviid bug, that is infected with trypanosoma cruzi.
Along with biting and blood meal, Metacyclic trypomastigote form present in feces are deposited on human skin.
Metacyclic trypomastigote form gets entry in to blood, when abraded skin, mucous membranes or conjunctivae become contaminated with reduviid bug’s feces containing infective form of the parasite.
T. cruzi can also be transmitted by laboratory accidents, blood transfusion, organ transplantation, vertical transmission from mother to child and rarely by contaminated food or drinks.
After entry in to the blood, the parasite invades reticuloendothelial cells (macrophage) and tissues like, muscles, epithelial cells, nervous tissues.
In side macrophage, there is formation of parasitophorous vacuole.
These parasitophorous vacuole fuses with lysosomes. Inside vacuole it transforms into amastigote form.
Followed by rupture of vacuole and release of amastigote in cell cytosol.
Amastigote multiply by binary fission forming a cyst like mass of growth known as pseudocyst.
Many amastigotes within pseudocyst are transformed into motile nonmultiplying trypomastigote forms.
On rupture of the pseudocyst, trypomastigotes are liberated to blood.
Liberated trypomastigotes are of two types:
1. Slender highly motile forms
2. Broader less motile forms
Slender highly motile have elongated nucleus, subterminal kinetoplast and short free flagellum. They are invasive form and migrate to many organs, penetrate cells and continue the life cycle.
Broader less motile have oval nucleus, terminal kinetoplast and long free flagellum. They persist in blood and are taken up by insect vector during blood meal.
Further development occurs in vector reduviid bugs.
