Giardiasis

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Medical Author:

Betsy P Schrader, MD

Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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• Giardiasis Overview
• Giardiasis Causes
• Giardiasis Symptoms
• When to Seek Medical Care
• Giardiasis Diagnosis
• Giardiasis Treatment
• Giardiasis Self-Care at Home
• Giardiasis Medications
• Giardiasis Follow-up
• Giardiasis Prevention
• Giardiasis Prognosis
• Synonyms and Keywords
• Author and Editor
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Giardiasis is an infection of the small bowel by a single-celled organism called Giardia lamblia. People become infected with the Giardia parasite after swallowing Giardia cysts often found in water contaminated by raw sewage or animal waste.

• Giardiasis can be found among 2% to 5% of people in industrialized nations such as the United States. In developing countries, up to 33% of the population may have had giardiasis. In the US, it is the most common intestinal parasitic disease.
• Travelers to foreign countries may develop diarrhea often caused by Giardia.

Giardia cysts are transmitted to humans in various ways.

• Contaminated water supplies: Giardia is one of the most common causes of water-borne diarrhea outbreaks. Sources of contaminated water include public facilities that improperly filter and treat water, water in developing countries, or rivers and lakes used by hikers. Overseas travelers and hikers are at a high risk for infection.
• Contaminated food: Food that may have been washed in contaminated water, exposed to manure, or prepared by an infected person can transmit the disease.
• Person-to-person contact: Infection may be caused by poor hygiene and most commonly occurs in daycare centers, nursing homes, and during oral-anal sexual contact. Up to 50% of children infected with Giardia in daycare centers, and up to 20% of infected sexually active homosexual males, pass cysts in their stool. Family members, daycare workers, and others in contact with infected stool may then themselves become infected.

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