Giardiasis is an infection of the small intestine caused by a tiny parasite called Giardia lamblia.

Giardia; Traveler's diarrhea - giardiasis

The 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:

• Are exposed to a family member with giardiasis
• Drink water from lakes or streams where animals such as beavers and muskrats, or domestic animals such as sheep, have left their waste
• Eat raw or undercooked food that has been contaminated
• Have direct person-to-person contact in day care centers, long-term care homes, or nursing homes
• Have unprotected anal sex

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

The time between infection and symptoms is 7 - 14 days.

Some people with Giardia have no symptoms.

Diarrhea is the main symptom. Other symptoms include:

• Gas or bloating
• Headache
• Loss of appetite
• Low-grade fever
• Nausea
• Weight loss and loss of body fluids

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

Tests that may be done include:

• Stool antigen test to check for Giardia
• Stool ova and parasites exam
• String test (rarely performed)

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

Medicines may be used for:

• Severe symptoms or symptoms that do not go away
• People who work in a day care center or nursing home to avoid spreading the disease

Most people respond to treatment. A change in antibiotic therapy will be tried if symptoms do not go away. Side effects from some of the medications used to treat this condition include:

• Metallic taste in the mouth
• Nausea
• Severe reaction to alcohol

In most pregnant women, treatment should wait until after delivery. Some drugs used to treat the infection can be harmful to the unborn baby.

• Dehydration
• Malabsorption (inadequate absorption of nutrients from the intestinal tract)
• Weight loss

Call your health care provider if:

• Diarrhea or other symptoms last for more than 14 days
• You have blood in the stool
• You are dehydrated

Purify all stream, pond, river, lake, or well water before drinking it. Use methods such as boiling, filtration, or iodine treatment.

Workers in day care centers or institutions should use good handwashing and hygiene techniques when going from child to child or patient to patient.

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

Peel or wash fresh fruits and vegetables before eating them.

DuPont HL. Approach to the patient with suspected enteric infection. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsever; 2011:chap 291.

Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsever; 2011:chap 142.

Giannella RA. Infectious enteritis and proctocolitis and bacterial food poisoning. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2010: chap 107.