A protozoan parasite capable of causing infectious diarrheal disease and is a significant cause of morbidity and mortality as a waterborne or foodborne illness for international travelers. It infects nearly 35% of people in developing countries and is the most common intestinal parasitic disease affecting humans.

Clinical Presentation

  • Flatulence 
  • Nausea/Vomiting/Diarrhea
  • Foul smelling stools
  • Steatorrhea
  • Abdominal cramps
  • Dehydration 
  • Weight loss
  • Failure to thrive


  • Good hygiene (before preparing food, eating, caring for patients, after using the toilet)
  • Minimize contact with animal feces as it is transferable between animals and humans
  • Drink safe water
    • Bottled water
    • Drinks with no ice
    • Boil water for at least 10 minutes
    • Use a filter (NSF 53 or 58 filter for cyst and oocyte reduction)


Symptoms usually resolve in 5-7 days with treatment


  • Keep patient hydrated and attempt to defer treatment until after first trimester
  • Paromomycin can be used
  • Avoid metronidazole or tinidazole

Breast Feeding

  • Mebendazole and Paromomycin are ok for breastfeeding mothers
  • Tinidazole and Metronidazole are contraindicated
  • Unknown effects with nitazoxanide or albendazole

Article by Julie Teuber, MD


  1. Prevention and Treatment of Giardia. Uptodate. Accessed July 2016.
  2. Giardia. CDC
  3. Granados CE, Reveiz L, Uribe LG, Criollo CP. Drugs for treating giardiasis (Review). Cochrane Database Syst Rev. 2012;12
  4. Tinidazole Drug Information. UptoDate. Accessed July 2016
  5. Centers for Disease Control (CDC). Neonatal deaths associated with use of benzyl alcohol—United States. MMWR Morb Mortal Wkly Rep. 1982;31(22):290-291.