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Questions and Answers
What is the infective stage of Babesia spp. for humans?
Which morphology of Babesia spp. is typically found in the intraerythrocytic stage?
What characteristic is true about the life cycle of Plasmodium spp. compared to Babesia spp.?
What is the role of rodent hosts in the lifecycle of Babesia spp.?
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Which stage of Plasmodium vivax is characterized by the presence of Schüffner’s dots?
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What is the correct sequence of the life cycle of a tsetse fly?
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Which statement accurately describes the habitat of Trypanosoma cruzi?
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What is the mode of transmission for Trypanosoma cruzi in humans?
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Which form of Trypanosoma cruzi is found in peripheral blood?
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Which organism is the primary vector for transmitting Chagas' disease?
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Study Notes
Plasmodium vivax
- Ring Stage: A thin rim of cytoplasm with chromatin dots present
- Trophozoite Stage: Vacuoles and Schüffner’s dots are present
- Schizont Stage: The parasitic stage is characterized by multiple nuclei
- Gametocyte Stage: The stage is characterized by Malaria pigments present
Plasmodium falciparum
- Ring Stage: A thin rim of cytoplasm with a single chromatin dot present
- Gametocyte Stage: The stage is characterized by multiple nuclei
Babesia spp., "Babesiosis"
- Distribution: The parasite is found in many parts of the world including the USA and Europe
- Habitat: The parasite lives within red blood cells (intraerythrocytic)
- Definitive Host (DH) and Vector: Hard ticks
- Intermediate Host (IH): Humans
- Reservoir Host (RH): Rodents and Cattle
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Morphology:
- Sporozoites: Pear-shaped and found in the salivary glands of ticks
- Intraerythrocytic Stages: Ring form with thin cytoplasm and large chromatin, and merozoites (2-5 µm) which can be pyriform, spherical, or ovoid. The merozoites can be single, paired, or in tetrads, which are known as Maltese Cross.
Trypanosomes
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Monomorphic Trypanosomes: A type of Trypanosome with a characteristic C-shape
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Trypanosoma cruzi:
- Distribution: Central and South America, but found in other areas due to migration
- Habitat: Lives within macrophages and cells of mesenchymal origin, including liver, thyroid, muscle, smooth muscle, bone marrow, lung, brain, etc.
- DH: Humans
- Vector: Triatomine winged bugs (Triatoma megista, T.infestans)
- RH: Armadillos, dogs, cats, and rodents.
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Morphology:
- In Humans: Trypomastigotes in blood (C-shaped, 20 µm, large kinetosome) - Inside cells, they transform into amastigotes
- In the midgut of the bug: Trypomastigotes change into epimastigotes, which pass to the hindgut and then stool.
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Trypanosoma cruzi:
Trypanosoma cruzi Amastigote
- Morphology: 2-5 µm, oval or rounded, present in cells
Life Cycle of Trypanosoma cruzi
- Infective Stages: Short metacyclic form, merozoites (blood transfusion)
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Mode of Infection:
- Contamination of bite wounds by feces or urine of infected Triatoma spp.
- Congenital transmission
- Blood transfusion
- Organ transplantation
- Consumption of food contaminated with bug feces.
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Mode of Transmission: Cyclopropagative, 10 days (asexual and sexual cycles in the intestine, asexual cycle in tissues)
- IH: Rodents (asexual cycle in tissues)
- Accidental (non-specific host): All mammals including humans, domestic and farm animals, birds, and reptiles (asexual cycle in tissues).
- Habitat: Obligate intracellular parasite, capable of invading any nucleated cell
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Morphology:
- Trophozoites: 4-6µ x 2-3 µ, crescent or ovoid in shape with a central nucleus.
- Pseudocysts: Formed when trophozoites invade a cell and multiply rapidly (tachyzoites) giving a cell containing up to 100 tachyzoites
- Tissue cysts: 10-200 µ, containing up to 60000 bradyzoites, which can be present in any tissue but mainly found in muscle and nervous tissue. Formed 1-2 weeks after infection with the development of an immune response.
- Oocyst: 9 x 12 µ, shed with the stool of cats. It is immature and non-infective freshly passed. It needs 1-5 days to sporulate and become infective (disporocystic-tetrazoic oocyst).
Toxoplasma gondii
- Tachyzoites: 4x2 µ, crescent shape, pointed anterior end, rounded posterior end, central nucleus
- Bradyzoites: Found in Pseudocysts and Tissue cysts
- Pseudocysts: Not a true cyst wall
- Tissue Cysts: Has a true cyst wall, 10-200 µ, containing up to 60,000 bradyzoites. Found in brain tissue
Wuchereria bancrofti
- Microfilaria: a microscopic larval stage
Leishmania
- Promastigote: Characterized by a single flagellum and nucleus
- Amastigote: Characterized by a nucleus and kinetoplast
Polymorphic Trypanosomes
- Flagellum: Long whip-like structure
- Undulating membrane: A membrane that runs along the length of the flagellum
Monomorphic Trypanosomes
- Kinetoplast: A structure containing mitochondrial DNA
Trypanosoma cruzi Amastigote in Heart Muscle
- Morphology: The amastigote stage without flagellum is present in heart muscle.
Diagnostic Stage for African Trypanosomiasis
- The diagnostic sage is the Trypanosome in the blood, characterized by a flagellum and undulating membrane
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Description
Test your knowledge on the life stages and characteristics of Plasmodium vivax, Plasmodium falciparum, and Babesia spp. This quiz covers key features including morphology, habitats, and host relationships. Perfect for students studying parasitology or infectious diseases!
