Giardiasis

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Basics

Description

  • Intestinal infection caused by the protozoan parasite Giardia lamblia:
    • G. lamblia is also called Giardia duodenalis and Giardia intestinalis.
  • Life cycle consists of cyst and trophozoite stages. Infection results from ingestion of cysts, which transform into trophozoites and colonize the small intestine to cause symptoms. Cysts can maintain viability for several months in cold water sources
    • The infectious cycle is continued when trophozoites encyst in the large intestine to be subsequently transmitted through water, food, or hands contaminated by feces of an infected person.
  • Most infections result from fecal–oral transmission or ingestion of unfiltered surface water (e.g., contaminated swimming areas).
  • Less commonly acquired through contaminated food

Epidemiology

  • Predominant age:
    • All ages but most common in early childhood (ages 1 to 9 years) and adults 35 to 44 years
  • Predominant gender:
    • Male > female (slightly)
  • Minimal seasonal variability; slight increase in summer and early fall, July through October
  • Over 1 million estimated Giardia-related illnesses annually in the U.S.

Pediatric Considerations

  • Most common in early childhood
  • Chronic infection in children can lead to intestinal malabsorption (may also be associated with growth restriction).

Prevalence
  • 10% of cases of traveler’s diarrhea are caused by parasites, most commonly Giardia (1).
  • >19,000 cases per year from U.S. states where Giardia is reportable:
    • Giardia is currently not reportable in Indiana, Kentucky, Mississippi, North Carolina, and Texas.

Etiology and Pathophysiology

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

Genetics
No known genetic risk factors

Risk Factors

  • Childcare centers
  • Anal intercourse
  • Wilderness camping
  • Travel to developing countries
  • Children adopted from developing countries
  • Public swimming pools
  • Pets with Giardia infection/diarrhea

General Prevention

  • Hand hygiene
  • Water purification when camping and when traveling to developing countries. Boiling is most effective.
  • Properly cook all foods.
  • Protect public water supply from fecal contamination.
  • Sanitary disposal of feces.

Commonly Associated Conditions

Hypogammaglobulinemia, IgA deficiency, and immunosuppression are associated with prolonged course of the disease and treatment failures.

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Basics

Description

  • Intestinal infection caused by the protozoan parasite Giardia lamblia:
    • G. lamblia is also called Giardia duodenalis and Giardia intestinalis.
  • Life cycle consists of cyst and trophozoite stages. Infection results from ingestion of cysts, which transform into trophozoites and colonize the small intestine to cause symptoms. Cysts can maintain viability for several months in cold water sources
    • The infectious cycle is continued when trophozoites encyst in the large intestine to be subsequently transmitted through water, food, or hands contaminated by feces of an infected person.
  • Most infections result from fecal–oral transmission or ingestion of unfiltered surface water (e.g., contaminated swimming areas).
  • Less commonly acquired through contaminated food

Epidemiology

  • Predominant age:
    • All ages but most common in early childhood (ages 1 to 9 years) and adults 35 to 44 years
  • Predominant gender:
    • Male > female (slightly)
  • Minimal seasonal variability; slight increase in summer and early fall, July through October
  • Over 1 million estimated Giardia-related illnesses annually in the U.S.

Pediatric Considerations

  • Most common in early childhood
  • Chronic infection in children can lead to intestinal malabsorption (may also be associated with growth restriction).

Prevalence
  • 10% of cases of traveler’s diarrhea are caused by parasites, most commonly Giardia (1).
  • >19,000 cases per year from U.S. states where Giardia is reportable:
    • Giardia is currently not reportable in Indiana, Kentucky, Mississippi, North Carolina, and Texas.

Etiology and Pathophysiology

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

Genetics
No known genetic risk factors

Risk Factors

  • Childcare centers
  • Anal intercourse
  • Wilderness camping
  • Travel to developing countries
  • Children adopted from developing countries
  • Public swimming pools
  • Pets with Giardia infection/diarrhea

General Prevention

  • Hand hygiene
  • Water purification when camping and when traveling to developing countries. Boiling is most effective.
  • Properly cook all foods.
  • Protect public water supply from fecal contamination.
  • Sanitary disposal of feces.

Commonly Associated Conditions

Hypogammaglobulinemia, IgA deficiency, and immunosuppression are associated with prolonged course of the disease and treatment failures.

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