Life cycle Entamoeba Histolytica Flashcards
What is the classification of Entamoeba Histolytica?
Extracellular Protozoa in the category Rhizopoda
How is Entamoeba Histolytica transmitted?
Contaminated food or water
What are the steps of the Entamoeba Histolytica lifecycle in the human host?
- Cysts and trophozoites are passed in feces.
- Cysts are typically found in formed stool whereas trophozoites are usually found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts
- Excystation occurs in the small intestine and trophozoites are released
- Trophozoites which migrate to the large intestine. During an non-invasive infection the trophozoites remain confined in the intestinal lumen with individuals continuing to pass cysts in their stool.
- The trophozoites multiply in the large intestine by binary fission and produce cysts and trophozoites. The cysts grow and both stages are passed in the feces.
What are the lifecycle steps of Entamoeba Histolytica lifecycle outside of the human host?
- Cyst can survive days to weeks in the external environment and remain infective due to their protection convert by their walls. Trophozoites passed in the stool are rapidly destroyed outside of the body. If ingested they will not survive exposure to the gastric environment.
- Humans will get infected when they ingest contaminated food or water.
What type of life cycle does Entamoeba histolytica have?
Direct life cycle. The human is the intermediate host
What are the symptoms of Entamoeba Histolytica infection?
Often it’s asymptomatic but 10-20% of infections can be fatal due to invasive amebiasis in the form of policis or liver abscess.
There are different levels of infection with symptoms:
Noninvasive colonization: in the flat part of the large intestine
Intestinal disease: Ascending part of the large intestine
Extra-intestinal disease lesions: (Liver) abscesses, hepatic amebiasis, pulmonary amebiasis, and cerebral amebiasis.
How does Entamoeba Histolytica cause symptoms?
The parasite has surface enzymes that can digest epithelial cells and therefore hydrolyze host tissues and cause pathology. Usually the hosts’ repair of the epithelial cells can keep pace with the damage. This is non-invasive infection. However when the host is stressed, has too much HCl, or a high bacterial flora, the digestion will be ahead of repair, causing intestinal-or extra-intestinal disease.
Where is Entamoeba Histolytica endemic?
Tropical areas with poor sanitary conditions
How is Entamoeba Histolytica diagnosed?
Microscopy for identification of cysts and tropozoites in stool. However cannot differentiate different non pathogenic Entamoeba species from Histolytica
Differentiation through isoenzymatic or immunolocial assays (antibody or antigen detection)
Or PCR can also differentiate
