Giardiasis is an infection of the small intestine caused by a tiny parasite (protozoa) called Giardia lamblia.
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 with the parasite
- Have direct person-to-person contact in day care centers, long-term care homes, or nursing homes with people who are infected with the parasite
- 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 becoming infected and symptoms is 7 to 14 days.
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.
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:
- Severe symptoms or symptoms that do not go away
- People who work in a day care center or nursing home, so that they do not spread the disease
Treatment is successful for most people. 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
- Severe reaction to alcohol
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.
When to Contact a Medical Professional
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 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;
DuPont HL. Approach to the patient with suspected enteric infection. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine
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
Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine
Update Date 5/12/2014
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.