Amoebiasis: Difference between revisions
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<br><b>Background Information</b> | <br><b>Background Information</b> | ||
First identified by Hippocrates around 300 B.C., amoebiasis is a gastrointestinal infection due to the amoeba, Entamoeba histolytica. Throughout the world, amoebiasis is the second leading cause of death from a parasitic disease with an estimated 70,000 deaths per year. However, most of these cases occur in the developing world. Although it | First identified by Hippocrates around 300 B.C., amoebiasis is a gastrointestinal infection due to the amoeba, Entamoeba histolytica. Throughout the world, amoebiasis is the second leading cause of death from a parasitic disease with an estimated 70,000 deaths per year. However, most of these cases occur in the developing world. Although it is the second leading cause of death from parasitic diseases, about 90% of the people exposed to E. histolytica are asymptomatic. | ||
E. histolytica secretes proteinases that do considerable damage to the host. They can dissolve the tissues of the host by killing the host cells on contact and they can engulf the red blood of the host. | |||
For those that do experience the symptoms associated with the Entamoeba histolytica infection, the onset is variable; they can occur gradually or very quickly. Gradual symptoms most often include a slow onset of colitis, or inflammation of the colon. Associated with colitis is diarrhoea and abdominal pain. Diarrhoea usually begins mildly and develops into diarrhoea that contains blood and mucous. Other signs of colitis are nausea, headache, and fever. On the other hand, symptoms that occur quickly and intensely include semi liquid stools that contain blood and mucous. Abdominal pain can range from mild to severe, frequently accompanied by a high fever and a tender liver. | For those that do experience the symptoms associated with the Entamoeba histolytica infection, the onset is variable; they can occur gradually or very quickly. Gradual symptoms most often include a slow onset of colitis, or inflammation of the colon. Associated with colitis is diarrhoea and abdominal pain. Diarrhoea usually begins mildly and develops into diarrhoea that contains blood and mucous. Other signs of colitis are nausea, headache, and fever. On the other hand, symptoms that occur quickly and intensely include semi liquid stools that contain blood and mucous. Abdominal pain can range from mild to severe, frequently accompanied by a high fever and a tender liver. | ||
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Entamoeba histolytica can be transmitted a number of ways, but most commonly is it transferred from fecal matter, where Entamoeba histolytica cysts are present, to oral ingestion. It is also transmitted from contaminated food or water sources, which are common in places such as Mexico, Central America, and South Asia. Some researchers have suggested a zoonosis pathway may also exist, but further studies still need to be conducted to prove this. | Entamoeba histolytica can be transmitted a number of ways, but most commonly is it transferred from fecal matter, where Entamoeba histolytica cysts are present, to oral ingestion. It is also transmitted from contaminated food or water sources, which are common in places such as Mexico, Central America, and South Asia. Some researchers have suggested a zoonosis pathway may also exist, but further studies still need to be conducted to prove this. | ||
<br><b>Entamoeba histolytica Lifecycle</b> | <br><b>Entamoeba histolytica Structure ans Lifecycle</b> | ||
While existing in the cyst portion of its life cycle, Entamoeba histolytica tend to have a diameter of 10–15μm and are round in shape. Within a refractile wall containing chitin, are four nuclei, glycogen, and chromatoid bodies (ribosomal assemblies). As a trophozoite, E. histolytica are generally larger, of around 10 to 50μm in diameter. Unlike the cyst form, the trophozoites a | |||
Once ingested by a human or a non-human primate, who are the natural hosts to the parasite, the E. histolytica cysts travel to the small intestine and become trophozoites in either the terminal ileum or colon (each cyst will produce eight trophozoites). Cysts can exist outside the human body for long periods of time (from days or even up to months in damp conditions and ideal temperatures), Unlike cysts, trophozoites cannot survive outside of this preferred environment, and will degrade very quickly if exposed to an outside environment. The incubation period of the amoeba can vary from a couple of days to as long as a year. Nonetheless, once in the small intestine, the trophozoites will attack the intestinal epithelial cells of the gastrointestinal tract. Not only do they invade the gastrointestinal track, but trophozoites can also migrate to other organs of the body and cause infection there as well. | |||
E histolytica trophozoites are highly motile, with a pleomorphic shape (diameter varying from 10 to 50 μm; figure 1). The fuel for this constant motion comes from the anaerobic conversion of glucose and pyruvate to ethanol.3E histolytica has no mitochondria (probably through secondary loss), but many of its metabolic enzymes seem to be of prokaryotic origin, possibly acquired from the lateral transfer of genes from bacteria. 4, 5 and 6 Trophozoites ingest bacteria and food particles, reproduce by binary fission, and encyst within the colon, completing the lifecycle when infectious cysts are excreted into the environment in stool. Trophozoites may exit in the stool as well, but they cannot survive outside the human host. The signals leading to encystation or excystation are poorly understood, but findings in the related reptilian parasite Entamoeba invadens suggest that ligation of a surface galactose-binding lectin on the surface of the parasite might be one trigger for encystation. | |||
It also uses pyrophosphate instead of ATP | It also uses pyrophosphate instead of ATP | ||
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"E. histolytica contains proteolytic enzymes (collagenase and neutral proteases) and cysteine proteases, which presumably facilitate its tissue invasion. The parasite also elaborates a range of enzymes on the amebic surface, including membrane-associated neuraminidase and β-glucosaminidase (166, 223, 234)." | "E. histolytica contains proteolytic enzymes (collagenase and neutral proteases) and cysteine proteases, which presumably facilitate its tissue invasion. The parasite also elaborates a range of enzymes on the amebic surface, including membrane-associated neuraminidase and β-glucosaminidase (166, 223, 234)." | ||
Revision as of 00:03, 3 December 2013
Introduction
Background Information
First identified by Hippocrates around 300 B.C., amoebiasis is a gastrointestinal infection due to the amoeba, Entamoeba histolytica. Throughout the world, amoebiasis is the second leading cause of death from a parasitic disease with an estimated 70,000 deaths per year. However, most of these cases occur in the developing world. Although it is the second leading cause of death from parasitic diseases, about 90% of the people exposed to E. histolytica are asymptomatic.
E. histolytica secretes proteinases that do considerable damage to the host. They can dissolve the tissues of the host by killing the host cells on contact and they can engulf the red blood of the host. For those that do experience the symptoms associated with the Entamoeba histolytica infection, the onset is variable; they can occur gradually or very quickly. Gradual symptoms most often include a slow onset of colitis, or inflammation of the colon. Associated with colitis is diarrhoea and abdominal pain. Diarrhoea usually begins mildly and develops into diarrhoea that contains blood and mucous. Other signs of colitis are nausea, headache, and fever. On the other hand, symptoms that occur quickly and intensely include semi liquid stools that contain blood and mucous. Abdominal pain can range from mild to severe, frequently accompanied by a high fever and a tender liver.
indications signs Those people infected and are asymptomatic, but who also do not have E. dispar create serum antibody responses to the parasite even in the absence of invasive disease.
"So far, E. dispar has never been recognized as a cause of colitis or amebic liver abscess, although infection with these amebae is much more common than with E. histolytica, especially in developed countries. Unlike in Japan (143), where E. histolytica infection is a problem in men who have sex with men, in the United States and Europe, E. dispar has been identified in most of these infections"
Transmission
Entamoeba histolytica can be transmitted a number of ways, but most commonly is it transferred from fecal matter, where Entamoeba histolytica cysts are present, to oral ingestion. It is also transmitted from contaminated food or water sources, which are common in places such as Mexico, Central America, and South Asia. Some researchers have suggested a zoonosis pathway may also exist, but further studies still need to be conducted to prove this.
Entamoeba histolytica Structure ans Lifecycle
While existing in the cyst portion of its life cycle, Entamoeba histolytica tend to have a diameter of 10–15μm and are round in shape. Within a refractile wall containing chitin, are four nuclei, glycogen, and chromatoid bodies (ribosomal assemblies). As a trophozoite, E. histolytica are generally larger, of around 10 to 50μm in diameter. Unlike the cyst form, the trophozoites a
Once ingested by a human or a non-human primate, who are the natural hosts to the parasite, the E. histolytica cysts travel to the small intestine and become trophozoites in either the terminal ileum or colon (each cyst will produce eight trophozoites). Cysts can exist outside the human body for long periods of time (from days or even up to months in damp conditions and ideal temperatures), Unlike cysts, trophozoites cannot survive outside of this preferred environment, and will degrade very quickly if exposed to an outside environment. The incubation period of the amoeba can vary from a couple of days to as long as a year. Nonetheless, once in the small intestine, the trophozoites will attack the intestinal epithelial cells of the gastrointestinal tract. Not only do they invade the gastrointestinal track, but trophozoites can also migrate to other organs of the body and cause infection there as well.
E histolytica trophozoites are highly motile, with a pleomorphic shape (diameter varying from 10 to 50 μm; figure 1). The fuel for this constant motion comes from the anaerobic conversion of glucose and pyruvate to ethanol.3E histolytica has no mitochondria (probably through secondary loss), but many of its metabolic enzymes seem to be of prokaryotic origin, possibly acquired from the lateral transfer of genes from bacteria. 4, 5 and 6 Trophozoites ingest bacteria and food particles, reproduce by binary fission, and encyst within the colon, completing the lifecycle when infectious cysts are excreted into the environment in stool. Trophozoites may exit in the stool as well, but they cannot survive outside the human host. The signals leading to encystation or excystation are poorly understood, but findings in the related reptilian parasite Entamoeba invadens suggest that ligation of a surface galactose-binding lectin on the surface of the parasite might be one trigger for encystation.
It also uses pyrophosphate instead of ATP
Prognosis/Treatment
The first successful treatment came about in 1912. Leonard Rogers used emetine. Today, those identified as infected by E. histolytica are treated with two types of drugs. The first is an amoebicidal agent as well as a luminal-acting cysticidal agent.
"E. histolytica contains proteolytic enzymes (collagenase and neutral proteases) and cysteine proteases, which presumably facilitate its tissue invasion. The parasite also elaborates a range of enzymes on the amebic surface, including membrane-associated neuraminidase and β-glucosaminidase (166, 223, 234)."
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Section 1
Therapy Developments of Amoebiasis
Section 2
Development of Diagnoses Methods It is important to have as precise methods as possible in detecting E. histolytica in order to determine the extent of the amoebiasis infection. Furthermore, the more that is understood about E. histolytic, researchers are better to develop treatments.
Microscopy/Biochemical Methods Microscopy has historically been the most prominent method of detecting E. histolytica. However, researchers are now discovering that it is difficult to to detect morphological differences among similar protozoa. There is another emerging problem becoming apparent with diagnosing amoebiasis with microscopy: ELISA
Serology only becomes positive about two weeks after infection.
Conclusion
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References
Edited by Kelsey Hauser, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2013, Kenyon College.
