Giardia infection

The giardia parasite lives in soilfoodand 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 marmotsbeavers and muskratsor domestic animals such as sheephave left their waste
• Eat raw or undercooked food that has been contaminated with the parasite
• Have direct person-to-person contact in daycare centerslong-term care homesor nursing homes with people who are infected with the parasite
• Have unprotected anal sex

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

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

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

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

Some people who have had a giardia infection for a long time continue having symptomseven 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 only mild symptomsno 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 daycare center or nursing hometo reduce the spread of disease

Antibiotic treatment is successful for most people. These include tinidazolenitazoxanide 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:

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

In most pregnant womentreatment 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.

These complications can occur:

• Dehydration (loss of water and other fluids in the body)
• Malabsorption (inadequate absorption of nutrients from the intestinal tract)
• Weight loss

Contact your health care provider if:

• Diarrhea or other symptoms last for more than 14 days
• You have blood in your stool (unusual)
• You are dehydrated

Purify all water from streamspondsriversand lakesor well water before drinking it. Use methods such as boilingfiltrationor 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.

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

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Melia JMPSears CL. Infectious enteritis and proctocolitis. In: Feldman MFriedman LSBrandt LJeds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. PhiladelphiaPA: Elsevier; 2021:chap 110.

Nash TEBartelt LA. Giardia lamblia. In: Bennett JEDolin RBlaser MJeds. MandellDouglasand Bennett's Principles and Practice of Infectious Diseases. 9th ed. PhiladelphiaPA: Elsevier; 2020:chap 279.

Updated by: Jatin M. VyasMDPhDRoy and Diana Vagelos Professor in MedicineColumbia University Vagelos College of Physicians and SurgeonsDivision of Infectious DiseasesDepartment of MedicineNew YorkNY. Also reviewed by David C. DugdaleMDMedical DirectorBrenda ConawayEditorial Directorand the A.D.A.M. Editorial team.