Giardia infection

Definition

Giardia, or giardiasis, is a parasitic infection of the small intestine. A tiny parasite called Giardia lamblia causes it.

Alternative Names

Giardia; G. duodenalis; G. intestinalis; Traveler's diarrhea - giardiasis

Causes

The giardia parasite lives in soil, food, and water. It may also be found on surfaces that have come into contact with animal or human waste.

You may become infected if you:

Travelers are at risk of giardiasis throughout the world. Campers and hikers are at risk if they drink untreated water from streams and lakes.

Symptoms

The time between becoming infected and symptoms is 7 to 14 days.

Non-bloody diarrhea is the main symptom. Other symptoms include:

Some people who have had a giardia infection for a long time continue having symptoms, even after the infection is gone.

Exams and Tests

Tests that may be done include:

Treatment

If there are no symptoms or only mild symptoms, no treatment may be needed. Some infections go away on their own within a few weeks.

Medicines may be used for:

Antibiotic treatment is successful for most people. These include tinidazole, nitazoxanide or metronidazole. A change in the type of antibiotic will be tried if symptoms do not go away. Side effects from some of the medicines used to treat giardia are:

In most pregnant women, treatment should not start until after delivery. Some drugs used to treat the infection can be harmful to the unborn baby.

People who take diuretics ("water pills") may need to stop taking these medicines if they have giardiasis. Never stop taking any medicine without first talking to your provider.

Possible Complications

These complications can occur:

When to Contact a Medical Professional

Contact your health care provider if:

Prevention

Purify all water from streams, ponds, rivers, and lakes, or well water before drinking it. Use methods such as boiling, filtration, or iodine treatment.

Workers in daycare centers or institutions should use good handwashing and hygiene techniques when moving from child to child or person to person.

Safer sexual practices may decrease the risk for getting or spreading giardiasis. People practicing anal sex should be especially careful.

Peel or wash fresh fruits and vegetables before eating them.

References

Fleckenstein JM. Approach to the patient with suspected enteric infection. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 262.

Hill DR. Giardiasis. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 322.

Melia JMP, Sears CL. Infectious enteritis and proctocolitis. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 110.

Nash TE, Bartelt LA. Giardia lamblia. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 279.



Review Date: 3/16/2024
Reviewed By: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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