Amoebiasis

Introduction to Amoebiasis

Amoebiasis is common parasitic infection of the gastrointestinal system caused by the protozoan Entamoeba histolytica. It is acquired through faeco-oral transmission.

Clinical features of Amoebiasis

Amoebiasis may present as:

Amoebic dysentery

  • Persistent mucoid/bloody diarrhoea
  • Abdominal pain
  • Fever/chills

Amoebic abscess

This can occur in any of the following forms as a result of spread via the blood stream:

  • Liver abscess: swelling, pain in the right sub costal area
  • Intracranial space-occupying lesion
  • Lungs: cough and blood stained sputum Amoeboma: swelling anywhere in the abdomen
  • Anal ulceration: may occur by direct extension from the intestinal infection

Chronic Carriers

  • Symptom-free

Differential diagnoses of Amoebiasis

  • Bacillary dysentery
  • Any other cause of bloody diarrhoea
  • Cancer of the liver
  • Other causes of liver enlargement

Complications of Amoebiasis

  • Rupture of abscess into the lungs, peritoneum,
  • space-occupying lesion in the brain,
  • right inguinal mass

Investigations

  • Stool: microscopy for cysts and motile. organisms (amoebic dysentery)
  • Full Blood Count
  • Serology: amoebic precipitin (if available)
  • Chest radiograph
  • Abdominal ultrasound scan (in amoebic liver abscess)

Treatment objectives

  • Rehydrate adequately
  • Eradicate the protozoa

Drug treatment for Amoebiasis

Amoebic dysentery

  • Correct dehydration

Metronidazole
Adult: 800 mg 8 hourly for 5 days
Child: 30 mg/kg/day in 3 divided doses for 5 days
Or:
Tinidazole
Adult: 2g daily orally for 3 days (with food)
Child: 50-60mg/kg daily for 3 days

Amoebic liver abscess

Metronidazole
Adult: 800 mg 8 hourly for 10 days
Child:50mg/kg/day in 3 divided doses for 7 10 days
Tinidazole
Adult: 2 g daily orally for 3 days (with food)
Child: 50-60mg/kg daily for 5 days

Asymptomatic cyst carriers

Treat cyst carrier if the patient is a food handler with:
Diloxanide furoate
Adult: 500 mg every 8 hours for 10 days
Child: over 25 kg: 20 mg/kg orally every 8 hours for 10 days.
Child:

  • under 25kg: ( I month – 12 years)- 6.6mg/kg every 8 hours for 8-10 days
  • 12 years to 18 years: 500mg every 8 hours for 10 days

Non-drug treatment

  • Aspiration is indicated to prevent spontaneous rupture of abscesses.
  • Consult a surgeon.

Notable adverse drug reactions, caution

  • Metronidazole is contraindicated in pregnancy.
  • Avoid alcohol during and at least 48 hours after treatment because of disulfiram like reaction to metronidazole

Prevention of Amoebiasis

  • Provision of safe drinking water
  • sanitary disposal of faeces
  • regular examination of food handlers and appropriate treatment where necessary.