Giardia Lamblia

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


Giardiasis is the most common parasitic cause of diarrhea throughout the world. Human infections most commonly result from the ingestion of contaminated water or direct fecal-oral transmission. When infection results from contaminated food, it is usually from infected food handlers or from washing food with contaminated water. The cyst form is environmentally resistant and can survive for greater than 1month in cool moist conditions. Infection is initiated by the ingestion of as few as 10 cysts which excyst into trophozoites that colonize the replicate in the small intestine. Infection can be asymptomatic, but those who develop symptoms typically have prolonged diarrhea with malabsorption and weight loss. Even after successful treatment a quarter of patients have prolonged irritable bowel syndrome. It is likely that most cases of human giardiasis result from direct or indirect transmission from other humans. Zoonotic transmission is well documented in a few outbreaks, but the extent of zoonotic transmission remains controversial. The most effective prevention strategy is maintenance of adequately pure sources of water used for consumption or recreational purposes. Food-borne transmission can be prevented by treatment of handlers known to be infected, by use of adequately purified water for washing food and by the appropriate use of hand washing and gloves by food handlers.

Original languageEnglish
Title of host publicationEncyclopedia of Food Safety, Second Edition, Volume 1-4
ISBN (Electronic)9780128225219
Publication statusPublished - 1 Jan 2023


  • Antigenic variation
  • Cyst viability
  • Diarrhea
  • Fecal oral transmission
  • Flagella
  • Malabsorption
  • Median body
  • Variant-specific surface protein (VSP)
  • Water purification
  • Water-borne transmission
  • Zoonosis


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