What is the pathophysiology of giardiasis?

Updated: Oct 01, 2018
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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Infection with Giardia intestinalis most often results from fecal-oral transmission or ingestion of contaminated water. Contaminated food is a less common etiology. Person-to-person spread is common, with 25% of family members with infected children themselves becoming infected.

Most infections are asymptomatic. The rate of symptomatic infection in the natural setting varies from 5-70%. Giardia is found in healthy people in endemic areas, and asymptomatic carriage with excretion of high numbers of cysts in stools is common.

Predisposing factors to symptomatic infection include hypochlorhydria, various immune system deficiencies, blood group A, and malnutrition. The incubation period averages 1-2 weeks, with a mean of 9 days. The average duration of symptoms in all ages ranges from 3-10 weeks.

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