Amoebiasis

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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 accounts for a large number of deaths every year, about 90% of the people exposed to E. histolytica are asymptomatic.

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 Lifecycle

Once ingested, the E. histolytica cysts travel to the small intestine and become trophozoites (each cyst will produce eight trophozoites). Cysts can exist outside the human body for long periods of time (up to days or even 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.

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)."



Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.


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Legend/credit: Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.
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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

Overall text length should be at least 1,000 words (before counting references), with at least 2 images. Include at least 5 references under Reference section.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.


Edited by Kelsey Hauser, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2013, Kenyon College.