Entamoeba histolytica (parasitic protozoan) life cycle | Amoebic dysentry

Entamoeba histolytica is a parasitic protozoan responsible for the disease amoebic dysentry.

Entamoeba histolytica life cycle :

There are two forms -

1. cyst : non-mobile form 

2. trophozoit :  Mobile form

 

A.Cyst entry : 

Injection of food or water contaminated with Entamoeba histolytica cyst will move through the mouth down the oesophagus into the stomach. Cysts are resistant to gastric environment and passes through the stomach.

B.Excystation :

Each cyst can divide and produce 8 trophozoits the mobile form of Entamoeba histolytica in the small intestine.

 

C.Multiplication :

The trophozoites will then move to colon of large intestine then multiply and colonizes.

Entamoeba can cause 2 types of infection: 

1. non-invasive: 90%

2. invasive : 10% 

1. Non-invasive : Trophozoits remain on the surface of mucus layer of colonic epithelium and multiplies by binary fission. This non-virulent form feeds on bacteria and detritus in lumen.

D. Encystation : The trophozoites will colonize in mucus layer and form new cysts. This is called encystation i.e; forming new cysts these cysts then exit out of the body in faeces. Cyst can infect new human by contamination.

2. Invasive : Trophozoits will invade mucus layer and Colonise inside colonic epithelial cells feeding on tissues. This will cause epithelial cells to lyse to die and this will create ulcer to large intestine. Trophozoits then invade into the bloodstream and target other organs such as Liver, lungs ,brain. Trophozoits can infect liver forming liver abscess or in lungs forming lungs abscesses rarely brain forming brain abscesses.

■ Pathogenicity : 

1. acute dysentery 

2. chronic stage:  intestinal ulcer , inflammation and necrosis with proteolytic enzyme .

3. heavy infection occur in intestine sclerosis hypertrophy and perforation .

4. blood and mucus in stool 

5. amoebic dysentery i.e; inflammatory diarrhoea.

6. painful gut area.

7. liver abscess long abscesses brain abscesses.

8. Leukocytosis

9. Colitis

10. ulcer

■ Symptoms : 

1. abdominal pain

2. weight loss 

3. bloody mucus diarrhoea

4.  intestinal lesions

■ Treatment : 

1. Metronidazole : Tissue amoebicide very effective in killing amoebas in the Wall of intestine, in blood and in liver abscess.

2.Diluxanide furoate : luminal amoebicide kills trophozoits and cysts in the lumen of the intestine.

■ Diagnosis : 

examining cyst in stool of patient .

■ Prevention : 

1. detection of Carriers and treatment of the sick will interrupt an epidemic.

2. hand washing after toilet and before handling or eating food.

3. proper excreta disposal specially from patients and cariers.

4. adequate and safe water supply.

5. control of flies.

6. cleanliness in food handling and preparation.