Giardiasis: A cause of Chronic diarrhea and malabsorption


Giardiasis is the Infection of the upper small intestine caused by a Flagellate Protozoan , Giardia lamblia ( aka G. intestinalis or G. duodenalis).


  • Occurs Worldwide, most abundantly in areas with poor sanitation.
  • Persons of all ages area affected, but is particularly high among children.

Life Cycle and Pathogenesis-

Organism occurs in faeces. Only the cyst is infectious, trophozoites are destroyed by gastric acidity. Cyst remains viable in water upto 3 months and are transmitted as a result of fecal contamination of water, food and from person to person.

Man is the only reservoir of infection.

Ingestion of as few as 10 cysts is sufficient to cause infection in the humans.  After the cysts are ingested trophozoites emerge in the Duodenum and Jejunum.

Trophozoites cause-

  • Epithelial damage
  • Atrophy of villi
  • Hypertrophic crypts
  • Cellular infiltration of lamina propria
  • Rarely, mucosal invasion.

Risk factors for infection– Hypogammaglobulinemia,  IgA deficiency,  Achlorhydria,  Malnutrition.

Clinical Features-

  • Incubation period= 1-3 days
  • Large proportion of infected person remain asymptomatic cyst carriers and their infections clear spontaneously
  • Prolonged diarrhea  specially froathy diarrhea with mucus.
  • With high episode of evacuation the stool becomes more watery, mucus . Blood may be seen.
  • Copious, froathy, malodorous and greasy
  • Less commonly anorexia, nausea, vomiting, mild epigastric discomfort, cramps, belching, flatulence, borborgymi, abdominal distension.
  • Marked weightloss, impaired growth and development is children.

Forms of Giardiasis-

  1. Acute diarrhea
  2. Chronic Diarrhea
  3. Malabsorption syndrome- marked weightloss, protein losing enteropathy, Vit A,B12 and dissacharide deficiency.


Stool RME- Samples obtained at 2-3 days interval on 3 separate occasions.Examine for the cyst

Duodenal fluid aspirate

Jejunla biopsy- Endoscopic.


Treatment options include-

  • Tinidazole Single dse 2 Gm
  • Metronidazole 2 Gm  daily for 3 days
  • Albendazole 400mg daily for 5 days

During Pregnancy-

  • Paromomycin 25-35mg/kg in 3 divided doses for 7 days

Reference- Harrison, Davidson, Lecture note



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