Giardia infection: MedlinePlus Medical Encyclopedia

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

T Causes
P 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.
P 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 daycare centers, long-term care homes, or nursing homes with people who are infected with the parasite
- Have unprotected anal sex
P Travelers are at risk for giardiasis throughout the world. Campers and hikers are at risk if they drink untreated water from streams and lakes.

T Symptoms
P The time between becoming infected and symptoms is 7 to 14 days.
P 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
P Some people who have had a giardia infection for a long time continue having symptoms, even after the infection is gone.

T Exams and Tests
P Tests that may be done include:
- Stool antigen test to check for giardia
- Stool ova and parasites exam
- String test (rarely performed)

T Treatment
P 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.
P Medicines may be used for:
- Severe symptoms or symptoms that do not go away
- People who work in a daycare center or nursing home, to reduce the spread of disease
P Antibiotic treatment is successful for most people. 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
P 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.

T Possible Complications
P 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

T When to Contact a Medical Professional
P Call your health care provider if:
- Diarrhea or other symptoms last for more than 14 days
- You have blood in your stool
- You are dehydrated

T Prevention
P Purify all stream, pond, river, lake, or well water before drinking it. Use methods such as boiling, filtration, or iodine treatment.
P Workers in daycare centers or institutions should use good handwashing and hygiene techniques when going from child to child or person to person.
P Safer sexual practices may decrease the risk for getting or spreading giardiasis. People practicing anal sex should be especially careful.
P Peel or wash fresh fruits and vegetables before eating them.

T Alternative Names
P Giardia; G. duodenalis; G. intestinalis; Traveler's diarrhea - giardiasis

T Patient Instructions
- Diarrhea - what to ask your doctor - child
- Diarrhea - what to ask your health care provider - adult

T Images
- Digestive system
- Giardiasis
- Institutional hygiene
- Digestive system organs

T References
P DuPont HL. Approach to the patient with suspected enteric infection. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 283.
P Haines CF, Sears CL. Infectious enteritis and proctocolitis and bacterial food poisoning. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 110.
P Nash TE, Hill DR. Giardiasis. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 351.
P Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 140.

T Review Date 3/13/2016
P 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.

