Giardiasis

Basics

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 the U.S.:
- 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 the U.S. (mostly from Northern States)
Fecal–oral transmission:
- Humans are major reservoir
- Waterborne and foodborne
- 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 the U.S.)
- 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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