Entamoeba histolytica is an ameba that feeds on cells in the human colon. It is the cause of amebic dysentery (bloody diarrhea) as well as colonic ulcerations. The infection is also referred to as amebiasis. If the organisms spread throughout the body via the bloodstream they may cause abscesses in the liver or, less frequently, other organs.
The organism has two forms. The cyst is round and 10-20 micrometers in diameter, and contains four nuclei when mature. It is resistant to desiccation and stomach acid, and can survive long enough in the environment to be spread to other humans. When the cyst reaches the large intestine, it excysts and the four nuclei present in the cyst become four separate amebae, each of which undergoes binary fission immediately; thus the ingestion of a single cyst leads to 8 trophozoites. The trophozoite, 10-60 micrometers in diameter, is the active form of the organism and it is in this form that the damage is done to the body. In 1994 the CDC recorded 2,983 cases of amebiasis in the United States.
E. histolytica is spread by the fecal-oral route. This is achieved through food or water contaminated with cysts, oral-anal sexual contact, or occasionally directly in childcare centers or institutions for the developmentally challenged. The disease is found far more frequently in people from developing countries or travelers to such areas than in developed countries.
Damage is caused by the lysis of epithelial cells, due in part to the insertion of pore-forming proteins into the membrane of the cell. Neutrophils and non-activated macrophages may also be killed and ingested by the organism, limiting the ability...
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...that brings about a mucosal immune response could be effective. However, the lack of projected profit limits the interest of pharmaceutical and biotechnology companies. Sanitation and hygiene are effective controls but often cannot be applied in many poor nations. Until a vaccine is created and distributed, Entamoeba histolytica will remain an important disease in mortality rates, especially among children in developing countries.
pharmacy school info on metronidazole and other treatments of amebiasis
CDC MMWR from march 08 1985
World Health Org cost-effectiveness study on treatment of asymptomatic carriers with metronidazole
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