Entamoeba histolytica
(Amoebic dysentery; Amoebiasis)
Amoebiasis
Amoebiasis is a disease cause by parasite Entamoeba histolytica in humans.
Amoebiasis also known as amoebic dysentery.
This pathogenic protozoan resides in upper part of large intestine in human bein.
Sources and Mode of Transmission
Infection occurs directly by ingestion of contaminated or water, with mature cyst of parasite.
Morphology
Anaerobic parasite
Parasite exist in three forms;
1. Prophozoite
Measures; 18-80 micrometre in diameter.
Trophozoites are motile by Pseudopodia.
Pseudopodia are long finger -like projection of ectoplasm into which endoplasm flows.
2. Precystic stage
Measures; 10-20 micrometre in diameter.
It is round and oval with blunt.
Pseudopodium
3. Cyst
Measures; 10-15 micrometre in diameter.
It is round
Pathogenesis and Clinical Significance
1. Amoebic dysentery; intestinal Amoebiasis ulcers.
Develop Extra intestinal Amoebiasis (hepatic Amoebiasis).
Parasite cause disease called amoebic dysentery.
Psthogen feed on RBCs of intestinal blood capillaries.
It damages intestinal mucosa by secreting enzyme; histolysis causes severe infection results in ulcers.
Cysts are also passed in feces and can infect other humans.
Incubation period; 1-4 weeks
From liver trophozoites enter into systemic circulation affect organ such as; lungs, brain, spleen, skin etc.
Life cycle
Parasite enters in host through ingestion of contaminated food or water with infective mature cyst.
Excystation (multiplication) occurs in host, releasing progency amoebas.
Which become active form called Trophozite in intestine, which penetrates in intestinal mucosa and may result in infection of liver and other organ and also ingest RBC.
They multiply by binary fission and cause tissue destruction.
Result abscess formation occurs.
Active form called cyst that pass in feces.
Ingestion of cyst through contaminated food or water.
Enter in small intestine.
Symptoms
Diarrhoea is often tinged with blood, called amoebic dysentery.
Abdominal pain
Repeated motion with mucus and blood.
Laboratory Diagnosis
Specimen collection
Stool sample, pus from hepatic abscess.
Stool examination
In normal saline
Stool antigen detection
ELISHA is used to detect antigen of Entamoeba histolytica.
Serological test
It is useful when microscopic examination is negative.
Intestinal Amoebiasis
In normal saline suspension, motile trophozoites or cysts are examined and identified directly under microscope.
Amoebic dysentery must be differenciated from bacillary dysentery.
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