Description

• Intestinal infection caused by the protozoan parasite Giardia lamblia:
  • G. lamblia is also called G. duodenalis and G. intestinalis.
• Infection results from ingestion of the cysts, which excyst into trophozoites:
  • Trophozoites colonize the small intestine and cause symptoms.
  • Cycle is continued when the trophozoites encyst in the small intestine and water, food, or hands are contaminated by feces of the infected person.
• Most infections result from fecal–oral transmission or ingestion of contaminated water (e.g., while swimming).
• Less commonly, giardiasis is the result of contaminated food.

Epidemiology

• Predominant age:
  • All ages, but most common in early childhood ages 1–9 and adults 35–44 (1)[A]
• Predominant gender:
  • Male > Female (slightly)
• There is minimal seasonal variability; however, a slight increase in cases is noted in the summer months (2).

Pediatric Considerations
Common in early childhood

• 5% of patients with stools submitted for ova and parasite exams
• >19,000 cases/year in reportable US states:
  • Giardia is not reportable in Indiana, Kentucky, Mississippi, North Carolina, and Texas.

Risk Factors

• Daycare centers
• Anal intercourse
• Wilderness camping
• Travel to developing countries
• Children adopted from developing countries
• Public swimming pools

Genetics
No known genetic risk factors

General Prevention

• Good hand washing when caring for diapered children
• Water purification when camping and when traveling to developing countries
• Cooking all foods

Pathophysiology

Giardia trophozoites colonize the surface of the proximal small intestine: The mechanism by which they cause diarrhea is unknown.

Etiology

Protozoan parasite (G. lamblia) infection acquired through fecal–oral transmission or ingestion of contaminated water, less commonly from contaminated food

Commonly Associated Conditions

Hypogammaglobulinemia and possibly IgA deficiency: Diarrhea more severe and prolonged in these patients