A protozoan infection of the upper small intestine transmitted by faecal-oral route.


  • Giardia lamblia (a flagellated protozoan)

Clinical features

  • Often asymptomatic
  • Prolonged diarrhoea, steatorrhoea
  • Abdominal cramps, bloating
  • Fatigue, weight loss
  • Malabsorption of fats and fat-soluble vitamins
  • Severe giardiasis may cause reactive arthritis, damage to duodenal, and jejunal mucosa

Differential diagnosis

  • Other causes of prolonged diarrhoea
  • Other causes of malabsorption


  • Stool: For cysts and trophozoites


  • Metronidazole 2 g after food daily for 3 days
    Child: 30 mg/kg (max: 1.2 g) per dose
  • Or tinidazole 2 g single dose
    Child: 50 mg/kg
  • Metronidazole, tinidazole: Avoid in first trimester, avoid alcohol during treatment and for 48 hours after
  • Metronidazole: Take after food


  • Provide health education on
    • Personal and food hygiene e.g. washing hands before handling or eating food and after using toilets
    • Proper disposal of human faeces
    • Use of safe clean drinking water