Giardiasis is a parasitic infection caused by Giardia lamblia. It is a case that can be seen worldwide but more common in developing countries.

Giardiasis is spread by the faeco oral route.

Pathogenesis of Giardiasis

Invasion of the upper small intestine by the parasite evokes inflammation, leading to progressive villous atrophy.

Giardia intestinalis infection causes enterocytes damage and loss of brush border of the epithelial cells of the intestine.

This leads to shortening of microvilli and altered epithelial barrier function.

Symptoms or Clinical features of Giardiasis

  • Acute disease: watery diarrhoea with abdominal bloating
  • Chronic disease: diarrhoea, steatorrhoea and weight loss from malabsorption syndrome with lactose intolerance, xylose malabsorption and vitamin B deficiency

Complications of Giardiasis

  • Diseases related to Vitamin B deficiency.

Occasionally, the under listed complications could occur

  • reactive arthritis
  • irritable bowel syndrome, and
  • recurring diarrhea that can last for years.

Among children in particular, severe giardiasis may delay physical and mental growth, slow development, and cause malnutrition.

Differential diagnoses

  • Other causes of upper gastrointestinal malabsorption such as coeliac disease and tropical sprue

Investigations and Diagnosis

  • Full blood count
  • Stool microscopy and faecal fat assessment
  • Jejunal biopsy

Treatment objectives

  • Rehydrate adequately
  • Eradicate parasite
  • Replace deficient nutrients

Drug treatment



  • 2g orally daily for 3 days or 400 mg 8 hourly for 5 days or 500mg 12 hourly for 7 -10 days


  • 1-3 years: 500 mg orally daily preferably in divided doses
  • 3-7 years: 600-800 mg daily in divided doses
  • 7-10 years: 1 g daily in divided doses for 3 days



  • 40 mg/kg orally as a single dose; or 2g stat, repeat after 1 week, once if necessary


  • 50 to 75 mg/kg as a single dose; repeat after 1 week

Supportive Care

  • Vitamin B supplementation
  • Avoidance of milk

Prevention of Giardiasis

Good sanitary habits, proper hand washing and/or use of alcoholic hand sanitizers. Uncontaminated water and food supplies


  1. Pubmed: Giardiasis
  2. CDC: Giardiasis Complications

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