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Questions and Answers
Infection of Entamoeba histolytica occurs by ingestion of ______, usually in contaminated water.
cysts
Decystation of Entamoeba histolytica occurs in the ______.
duodenum
T.vaginalis colonizes the ______ of women and the urethra of men.
vagina
Leishmaniasis is transmitted by the bite of infected female ______ sandflies.
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The sandflies inject the ______ stage, which reach the puncture wound and are phagocytized by macrophages.
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Promastigotes transform into ______ in macrophages and other types of mononuclear phagocytic cells.
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T.b.gambiense and T.b.rhodesiense have a single ______ and a single flagellum.
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The undulating membrane is joined to the body by a ______.
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The outer surface of the organism is densely coated with a layer of ______.
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The infective form of the trypanosome is injected into the primary host during a bite by the vector, the ______ fly.
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Trypomastigotes can traverse the walls of blood and lymph capillaries into the ______ tissues and, at a later stage, into the brain and cerebrospinal fluid.
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The life cycle passes in four stages: Three in man: ______ schizogony, Erythrocytic schizogony, Exo- erythrocytic schizogony, and One in mosquito Sporogony.
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During a blood meal, a malaria-infected female ______ mosquito inoculates sporozoites into the human host.
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The malaria parasite life cycle involves two ______.
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The anterior end of a trophozoite is ______ with cytosome.
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Diagnosis of Balantidium coli is done By demonstration of trophozoites and ______ in feces.
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Excystation occurs in the ______ intestine, and the trophozoites colonize the large intestine.
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The trophozoites reside in the lumen of the large intestine and ______ of humans and animals.
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During replication, ______ (sexual reproduction) may occur.
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The ______ host is the human.
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The ______ stage is the cercaria.
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Both ______ and adults take blood meals from the human host.
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Study Notes
Entamoeba Histolytica Life Cycle
- Infection occurs by ingesting cysts in contaminated water
- Decystation occurs in the duodenum, and trophozoites colonize the upper small intestine
- Trophozoites can attach to the sub-mucosal epithelium via the ventral suction disc or swim freely
- Free trophozoites encyst as they move downstream, and mitosis takes place during encystment
- Cysts are passed in the stool
- Humans are the primary host, but beavers, pigs, and monkeys can also be infected and serve as reservoirs
Trichomonas Vaginalis Life Cycle
- T. vaginalis colonizes the vagina of women and the urethra (sometimes prostate) of men
- Infection occurs primarily via sexual contact
- The organism does not encyst and divides by binary fission, which is favored by low acidity (pH 3.5-4.5)
- There is no non-human reservoir
Leishmaniasis Life Cycle
- Transmitted by the bite of infected female phlebotomine sandflies
- Sandflies inject promastigotes from their proboscis during blood meals
- Promastigotes are phagocytized by macrophages and other mononuclear phagocytic cells and transform into amastigotes
- Amastigotes multiply by simple division and infect other phagocytic cells
- Sandflies become infected by ingesting infected cells during blood meals
Morphology
- T.b. gambiense and T.b. rhodesiense measure 10-30 micrometers, have a single central nucleus and a single flagellum, and are densely coated with a layer of glycoprotein
Trypanosomiasis Life Cycle
- Infective form of the trypanosome is injected into the primary host during a bite by the vector, the tsetse fly
- Organism transforms into a dividing trypanosomal (trypomastigote) blood form as it enters the draining lymphatic and blood stream
- Trypanosomal form enters the vector during the blood meal and travels through the alimentary canal to the salivary gland
- Trypomastigotes can traverse the walls of blood and lymph capillaries into the connective tissues and, at a later stage, into the brain and cerebrospinal fluid
- The organism can be transmitted through blood transfusion
- The life cycle passes in four stages: pre-erythrocytic schizogony, erythrocytic schizogony, exo-erythrocytic schizogony, and sporogony
Malaria Life Cycle
- Involves two hosts: human and female Anopheles mosquito
- Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites
- Merozoites infect red blood cells
- Parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony)
- After initial replication in the liver (exo-erythrocytic schizogony), the parasites undergo asexual multiplication in the erythrocytes
Balantidium Coli
- Trophozoites are oval in shape, have two nuclei (macro-nucleus and micro-nucleus), and an anterior end pointed with cytosome and a posterior end rounded
- Cysts are spherical or oval in shape, have two nuclei (macro-nucleus and micro-nucleus), and are surrounded by a thick layer
- Life cycle: infection occurs when the host acquires the cyst through ingestion of contaminated food or water, excystation occurs in the small intestine, and trophozoites colonize the large intestine
- Trophozoites reside in the lumen of the large intestine and appendix of humans and animals, where they replicate by binary fission (asexual reproduction), and conjugation (sexual reproduction) may occur
- Trophozoites undergo encystation to produce infective cysts, and some trophozoites invade the wall of the colon and multiply, causing ulcerative pathology in the colon wall
Schistosomiasis Life Cycle
- Parasite eggs are released into the environment from infected individuals, hatching on contact with fresh water to release the free-swimming miracidium
- Miracidia infect fresh-water snails by penetrating the snail's foot
- In the snail, thousands of new parasites are produced, known as cercariae, which are the larvae capable of infecting mammals
- The definitive host is the human, and the intermediate host is the fresh-water snail
- The infective stage is the cercaria
- After encountering the skin, the cercariae penetrate and lose the tail, transforming into schistosomulae
Hookworm Life Cycle
- No specific details mentioned in the provided text
Lice Life Cycle
- Lice stages: egg/nit, nymph (3 molts), and adult
- Both nymphs and adults take blood meals from the human host
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Description
Learn about the life cycle of Entamoeba Histolytica, a parasitic protozoan that causes amoebiasis, from infection to encystment and transmission.
