Table of Contents
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.
Morphology
- Trophozoites
- 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)
- Fly
- Feaces
- Food
- 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.
Image Source: Your Article Library and CDC
Life cycle
- 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.
Pathogenesis
- 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.
Clinical finding
- Flask shaped ulceration in the colon
- Abdominal pain
- Diarrhea
- Vomiting
- Amoebic dysentery (blood & mucus in the stool)
Extraintestinal amoebiasis
-
Hepatic amoebiasis
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.
-
Cerebral amoebiasis
Transmitted from lever to heart and then move toward the brain to develop cerebral lesion.
Mild symptoms
- Diarrhea including pus and painful passages of stool.
- Stomach pain
- Nausea
- Stomach cramps
Severe symptom
- Amoebic dysentery
- Profuse diarrhea
- Liver abscess
- Severe ulceration
- Colitis
- Megacolon ameboma
Treatment
- The choice of treatment for symptomatic intestinal amebiasis or hepatic abscesses is metronidazole (Flagel)
- Trinidazole
- There should be no need to drained hepatic abscesses.
- Iodoquinol or paromomycin should be used for the treatment of asymptomatic cyst.
Prevention
- 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.
References
- https://www.healio.com/infectious-disease/gastrointestinal-infections/news/print/infectious-disease-news/%7Bc4864d2e-afa4-4f19-a159-81305359dc9c%7D/e-histolytica–a-formidable-gastrointestinal-infection
- https://www.hindawi.com/journals/cjgh/2018/4601420/
- https://emedicine.medscape.com/article/212029-overview
- https://www.emedicinehealth.com/amebiasis_entamoeba_histolytica_infection/article_em.htm
- https://www.cdc.gov/dpdx/amebiasis/index.html
- https://www.medicinenet.com/amebiasis_entamoeba_histolytica_infection/article.htm
- https://www.infectiousdiseaseadvisor.com/home/decision-support-in-medicine/infectious-diseases/entamoeba/
- https://www.britannica.com/science/Entamoeba-histolytica