What is the global incidence of giardiasis?

Updated: Oct 01, 2018
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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Giardia has a worldwide distribution, occurring in both temperate and tropical regions. It continues to be the most frequently identified human protozoal enteropathogen. Prevalence rates vary from 4-42%. In the industrialized world, overall prevalence rates are 2-5%. In the developing world, G intestinalis infects infants early in life and is a major cause of epidemic childhood diarrhea. Prevalence rates of 15-20% in children younger than 10 years are common. [32, 40]

Giardia is the most common gut parasite in the United Kingdom, and infection rates are especially high in Eastern Europe. Prevalence rates of 0.94-4.66% and 2.41-10.99% have been reported in Italy. [41]

A 2005 study demonstrated a Giardia infection rate of 19.6 per 100,000 population per year in Canada. [42] While the yearly incidence of the disease was stable, a significant seasonal variation was observed, with a peak in late summer to early fall, which correlates with the pattern found in the United States. [42] New Zealand reports more than 30 cases of giardiasis per 100,000 population every year, which is one of the highest among the industrialized countries. [43]

Giardiasis accounts for a relatively small percentage of traveler's diarrhea. It is more likely to be found as the cause of diarrhea that occurs or persists after returning home from travel to developing regions of the world due to its relatively long incubation period and persistent symptoms. Giardia has been identified as the causative agent in a large percentage of cases among travelers to the region of St. Petersburg, Russia, where tap water is the primary source.

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