Last Updated on January 23, 2020 by Sagar Aryal
Entamoeba histolytica– Morphology, Epidemiology, Life cycle, Pathogenesis, Clinical findings
- 500 Million populations are infected over the world.
- 60-70% population in Pakistan is infected
- Entamoeba histolytica caused amebic dysentery and liver abscess.
- A cyst (egg)
- Cyst= it is immovable and has disease-causing form.
- Cyst survives for a long period of time because it is double layered.
- Trophozite= they are motile and have a small shelf life so they cannot survive outside.
- Encystment (trophozoite –> cyst)
- Excystment (cyst –> trophozoite.
Transmission and Epidemiology
- Transmitted by the fecal-oral route.
- 5-F are the main source of transmission that includes:
- Finger (contaminated hands)
- Fomites (public places, door handles)
- 70-80% are transmitted via 5F or fecal-oral route
- Reaming 10-20% are transmitted by blood e.g. malaria, leishmania
- Infection by Entameba histolytica occur globally, but mostly in tropical countries due to poor sanitation, more infection will be there due to this reason.
- About 1% to 2% of people are affected in the United States.
- Infection is common in homosexuals means having anal sex.
- The cyst wall is resistant to gastric juice.
- Then Cyst reach to caecum or lower part of ileum due to alkaline medium
- Cyst wall damage by trypsin and lead to exystation.
- Metacystic trophozoites.
- Trophozoites in the colon (sometimes invade to blood & then to liver, brain, and lungs.
- Cyst 1-4 nuclei.
- Passed in feces.
- Cyst in contaminated food and water.
- Cyst ingested.
- Metacyst in the small intestine.
- Organism are entering into the host in the form of a cyst, which is transmitted through the fecal-oral route from contaminated water and food.
- Anal oral (male homosexuals) transmission also occurs.
- No animal reservoir
- In the ileum, the ingested cyst is differentiated into trophozoites
- But colonization in caecum and colon.
- After that trophozoite enters into colonic epithelium and secretion of enzyme takes place as a result of localized necrosis occur.
- Inflammation also is there.
- Lesions, when reached to mucosal layer flask-shaped ulcer, occur
- Much of the Intestine is damaged.
- Invasion of the portal circulation takes place in all of these results.
- Flask shaped ulceration in the colon
- Abdominal pain
- Amoebic dysentery (blood & mucus in the stool)
Transmit via portal vein from the intestine to the liver and caused liver inflammation after that infects diaphragm which leads to pulmonary amoebiasis that infects lungs.
Transmitted from lever to heart and then move toward the brain to develop cerebral lesion.
- Diarrhea including pus and painful passages of stool.
- Stomach pain
- Stomach cramps
- Amoebic dysentery
- Profuse diarrhea
- Liver abscess
- Severe ulceration
- Megacolon ameboma
- The choice of treatment for symptomatic intestinal amebiasis or hepatic abscesses is metronidazole (Flagel)
- There should be no need to drained hepatic abscesses.
- Iodoquinol or paromomycin should be used for the treatment of asymptomatic cyst.
- Avoid fecal contamination of food and water.
- Used good personal hygiene such as handwashing
- Municipal water supplies are also purified
- The human feces (night Soil) should not be used as a fertilizer in crops.
- Used cooked vegetables in endemic areas.