Life Cycle of Trypanosoma cruzi in the Human Host

Introduction

• The Trypanosoma cruzi life cycle begins with the infection of a human host by a triatomine insect.
• The insect, infected with T. cruzi, bites a human and releases metacyclic trypomastigotes through its feces near the bite area.

Entry into Host

• Metacyclic trypomastigotes enter the host through:
  • The bite site when scratched by the host.
  • Movement to mucosal-covered regions.
• Parasites reach the mammalian bloodstream.

Invasion of Host Cells

• Trypanosomes invade various cell types:
  • Macrophages
  • Muscle cells
  • Epithelial cells
  • Neurons
• Example observed: Attachment to macrophage surface.

Internalization Process

• Internalization via phagocytosis:
  • Formation of pseudopods.
  • Formation of parasitophorous vacuole.
• Fusion of host cell lysosomes with the vacuole.
  • Lysosomal content released but parasite remains unaffected.

Transformation and Replication

• Inside the vacuole, trypomastigote transforms into an amastigote.
  • Disruption of vacuole membrane.
• Amastigotes are released into host cell cytoplasm.
  • Divide multiple times, accumulating and occupying entire cytoplasm.

Transformation and Release

• Amastigotes transform back into trypomastigotes.
• Trypomastigotes exhibit intense movement.
• Burst out of the host cell into extracellular space and bloodstream.

Conclusion

• The cycle continues as trypomastigotes infect new cells in the host, perpetuating the life cycle of T. cruzi.