Amastigote

Definition

An amastigote is a non-flagellated, round or oval-shaped life stage of certain parasitic protozoa, particularly those that infect the circulatory and lymphatic systems. This intracellular form of the parasite is adapted to survive and replicate within the host's cells.

5 Must Know Facts For Your Next Test

1. Amastigotes lack a visible flagellum, unlike the motile, flagellated forms of these parasites.
2. Amastigotes are adapted to survive and replicate within the phagocytic cells of the host, such as macrophages and dendritic cells.
3. The amastigote form is the stage of the parasite's life cycle that is responsible for the clinical manifestations of diseases like leishmaniasis and Chagas disease.
4. Amastigotes can evade the host's immune defenses by inhibiting the microbicidal activities of the phagocytic cells they infect.
5. Identification of amastigotes in clinical samples, such as from skin lesions or bone marrow aspirates, is often used for the diagnosis of parasitic infections.

Review Questions

• Describe the key features that distinguish the amastigote form of parasitic protozoa from other life stages.
  • The amastigote form of parasitic protozoa, such as Trypanosoma and Leishmania, is characterized by its lack of a visible flagellum, round or oval shape, and adaptation to survive and replicate within the host's phagocytic cells, like macrophages and dendritic cells. This intracellular form of the parasite is responsible for the clinical manifestations of diseases like leishmaniasis and Chagas disease, and its identification in clinical samples is often used for diagnosis.
• Explain how the amastigote form of parasitic protozoa is able to evade the host's immune defenses.
  • Amastigotes have developed mechanisms to evade the host's immune system by inhibiting the microbicidal activities of the phagocytic cells they infect. This allows the parasites to survive and replicate within these host cells, which are normally responsible for engulfing and destroying foreign pathogens. The ability of amastigotes to persist and proliferate within the host's immune cells is a key factor in the pathogenesis of diseases caused by these parasitic protozoa.
• Analyze the role of the amastigote stage in the life cycle and transmission of parasitic protozoa that infect the circulatory and lymphatic systems.
  • The amastigote form of parasitic protozoa, such as Trypanosoma and Leishmania, is a critical stage in the parasite's life cycle and transmission. As the intracellular form adapted to survive and replicate within the host's phagocytic cells, the amastigote is responsible for the clinical manifestations of diseases like Chagas disease and leishmaniasis. The ability of amastigotes to evade the host's immune defenses and persist within the circulatory and lymphatic systems allows for the continued propagation and spread of these parasitic infections. Understanding the unique features and role of the amastigote stage is essential for developing effective diagnostic and treatment strategies for these parasitic diseases.

Related terms

Trypanosoma:

A genus of parasitic protozoa that causes diseases like Chagas disease and African sleeping sickness, with amastigotes as one of their life stages.

Leishmania:

A genus of parasitic protozoa that causes various forms of leishmaniasis, with amastigotes as the stage that infects and replicates within host cells.

Intracellular Parasite: A parasite that lives and reproduces inside the cells of its host, such as the amastigote form of certain protozoan parasites.