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Giardiasis is a topic covered in the 5-Minute Emergency Consult.

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  • Noninvasive diarrhea
  • Found worldwide:
    • 2–15% prevalence in developed nations
    • 20–40% prevalence in developing nations
  • 5% of all travelers’ diarrhea
  • Most common intestinal parasite in US:
    • Highest incidence in early summer months through fall
    • Highest incidence in children aged 1–9 yr and adults aged 30–39 yr
    • In 2010, 19,888 cases reported in US (mostly from Northern States)
  • Fecal–oral transmission:
    • Humans are major reservoir
    • Zoonotic reservoir in both domestic and wild mammals
    • Reservoir in contaminated surface water
  • Populations at risk:
    • Travelers to endemic areas (developing countries, wilderness areas of US)
    • Children in day care centers and their close contacts
    • Institutionalized persons
    • Practitioners of anal sexual activity


  • Giardia lamblia:
    • A protozoan flagellate
  • Also called Giardia intestinalis or Giardia duodenalis
  • Ingested Giardia attach to intestinal villi
  • Alters the intestinal brush-border enzymes, impairing digestion of lactose, and other saccharides
  • No toxin produced

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Rosen, Peter, et al., editors. "Giardiasis." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307381/all/Giardiasis.
Giardiasis. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307381/all/Giardiasis. Accessed April 24, 2019.
Giardiasis. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307381/all/Giardiasis
Giardiasis [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 24]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307381/all/Giardiasis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Giardiasis ID - 307381 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307381/all/Giardiasis PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -