Entamoeba dispar is identical to E. histolytica
in appearance but does not cause disease.
- Is due to the protozoan Entamoeba histolytica
- Ingestion of food or water contaminated by cysts
- Direct faecal-oral contamination of food
- Oral-anal sexual practices
- Insects may contaminate food
- Cyst stage - infective, a trophozoite stage which causes invasive disease
- Cysts are acquired from faecally contaminated water or uncooked food
- Cysts release trophozoites in the small intestine pass to the colon to produce "flask-like" colonic ulcers
- Trophozoites can pass via the portal vein to the liver to form a liver abscess
- Liver abscess: Caused as organisms pass via the portal vein to the liver.
- Worldwide tropics and subtropics
- Entamoeba histolytica (E. histolytica) is notifiable
- Amoebic dysentery: Invades colonic epithelium. Colitis with diarrhoea containing blood and pus. Abdominal pain. DFever, weight loss. Perforation is rare. May cause mild intermittent diarrhoea. Lead to Toxic megacolon, Chronic infection with stricture and Severe lower GI haemorrhage.
- Amoeboma: Inflammatory mass in colonic wall of Amoeba around sigmoid or caecum can be mistaken for a tumour
- Amoebic liver abscess: Incubation period 8-20 weeks. Patient is pyrexial, malaise, RUQ pain. Tender hepatomegaly. Rupture
can produce empyema, peritonitis, pericarditis.
- Pericardial amoebiasis: usually due to rupture of liver abscess
into pericardium. Presents as chest pain, dyspnea, tachycardia,
pulsus paradoxicus, hypotension
- Brain abscess : acute illness resembling pyogenic
abscess with headache, fever, neurologic signs indicating mass
- Cutaneous amoebiasis: usually seen near anus or on genitals.
Presents as painful skin ulcerations.
- FBC:anaemia. Raised WCC U&E: AKI CRP elevated
- Serology: amoebic fluorescent antibody test (FAT) 90% positive in liver disease and 70% in colitis
- Stool Microscopy: may need to send several. It shows motile trophozoites containing red blood cells and cysts.
- Colonic biopsy: Flask like ulcers. Strictures
- Chest X-ray can show elevated right diaphragm
and fluid in right chest.
- USS or Abdominal CT: Usually right lobe of the liver. raised ALP
- CT / MRI head for brain involvement
- Inflammatory bowel disease
- Bacillary dysentery
- Salmonella infection
- Pseudomembranous colitis
Differential of liver abscess
- Hydatid cyst
- Tumour primary or secondary
- Metronidazole 800 mg PO TDS for 5 days for amoebic colitis
- Metronidazole 400 mg TDS for 10-14 days for liver abscess. This is followed by Diloxanide 500 mg TDS for 10 days to clear the bowel of parasites. A follow up scan can be done.
- Occasionally liver aspiration required produces "anchovy paste" , chocolate coloured fluid. Usually done if cysts is at risk of rupture or medical therapy fails.
- Drink bottled water in the endemic area + good personal hygiene
- There is no effective vaccine