Introduction:
Entamoeba histolytica has become known
as the more serious of the amoeba parasitic infections [1]. Clinically, this parasite causes the disease amoebiasis
and the scientific name suggests that this parasite destroys the tissue of its
host leaving them with severe diarrhea, also known as dysentery [1], as well as
dehydration. In severe cases of infection, E. histolytica burrows through the
large intestine and travels through the blood stream to the liver where it
feeds and causes abscesses in the liver almost turning it into liquid [3]. It
directly infects humans through food and drink that have come into contact with
contaminated feces, or it can be spread by direct contact with contaminated
feces. There is no intermediate host for
this parasite. E. histolytica is found
worldwide, but it is seen more prominently in tropical regions than
elsewhere. There are some humans who are
more susceptible to get this parasite which is, but not limited to, homosexual
males, frequent travelers, and institutionalized populations [2].
Symbiont Description:
The genus of this species is Entamoeba,
and the species is histolytica. E.
histolytica lives and multiplies as a trophozoite, which is a growing stage in the life cycle of some
sporozoan parasites, when they are absorbing nutrients from the host [4]. This oblong trophozoite can only survive
within the host and fresh feces, after this stage of transmission the
trophozoite becomes a cyst that can survive in soil, water, and on foods until
it is consumed by the host. [3]
Host Description:
There is no
intermediate host in this parasites life cycle.
E. histolytica only infects humans making it a hologenous parasite. This parasite has been estimated to infect
almost fifty million people worldwide [1].
Life Cycle:
Mature cysts pass
from the large intestine through the host as feces. Once the host comes into
contact orally with contaminated feces, the cysts are ingested and passed
through the digestive system. Once in the small intestines, they transform back
into trophozoites and migrate to the large intestine. The parasite lives and
multiplies, by binary fission, within the large intestine. In severe
infections, E. histolytica can break through the large intestine and travel to
organs within the body via the blood stream. Once they come into contact with
the blood stream, they attach to it and cause abscesses to form. [3]
Ecology:
E. histolytica is
not specific to one region, but in industrialized nations they are known to
infect immigrants, institutionalized people, and recent travelers [3]. It is
easy to cure the minor infections of E. histolytica with two antibiotics:
Metronidazole and Tinidazole [1,3]. As long as the symptoms do not become
severe, it can be easily treated however if the infection becomes severe one
might require surgery to relieve the excess fluid built up around the organ [1].
Example of a
Shortened Life Cycle:
E. histolytica has
shortened its life cycle compared to most parasites. By having only one host,
Entamoeba histolytica does not have as many stages to go through and does not
have to rely on certain hosts to reach sexual maturity. [1]
References:
[1] Entamoeba
histolytica info. (2012). Retrieved from http://entamoebahistolytica.org.
Accessed February 27, 2012.
[2] Keas, A. (1999). Entamoeba
histolytica. Retrieved from https://www.msu.edu/course/zol/316/ehisgeo.htm.
[3] Parasites in humans find the nastiest parasites in
humans. (2010). Retrieved from http://www.parasitesinhumans.org/entamoeba-histolytica-amoebiasis.html
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