What is giardiasis?

Giardiasis is an illness caused Giardia lamblia, a one-celled, microscopic parasite that lives in the intestines of people and animals. During the past 15 years, Giardia lamblia has become recognized as one of the most common causes of waterborne disease in humans in the United States. This parasite is found in every region of the United States and throughout the world.

What are the symptoms of giardiasis?

Diarrhea, abdominal cramps, and nausea are the most common symptoms of giardiasis. These symptoms may lead to weight loss and dehydration. However, not everyone infected has symptoms.

How long after being infected do symptoms appear?

Symptoms usually appear 1-2 weeks after infection with the parasite.

How long will I have symptoms?

In otherwise healthy persons, symptoms may last 4-6 weeks. Occasionally, symptoms last longer.

How can I get giardiasis?

Who is at risk?

Persons at increased risk for giardiasis include child care workers; diaper-aged children who attend day care centers; international travelers; hikers; campers; and others who drink untreated water from contaminated sources. Several community-wide outbreaks of giardiasis have been linked to drinking municipal water contaminated with Giardia.

What should I do if I think I have giardiasis?

See your health care provider who will ask you to submit stool samples to see if you are harboring the parasite. Because Giardia can be difficult to diagnose, your health care provider may ask you to submit several stool specimens over several days.

What is the treatment for giardiasis?

Several prescription drugs are available to treat Giardia.

How can I prevent giardiasis?

My water comes from a well; should I have my well water tested?

Consider having your well water tested if you answer yes to the following questions:

Tests specifically for Giardia are expensive, difficult, and usually require hundreds of gallons of water to be pumped through a filter. If you answered yes to the above questions, consider testing your well for fecal coliforms instead of Giardia. Although fecal coliform tests do not specifically test for Giardia, testing will show if your well has fecal contamination. If it does, the water is likely to be contaminated with Giardia, as well as other harmful bacteria and viruses. Look in your local telephone directory for a laboratory or cooperative extension that offers water testing.

My child was recently diagnosed as having giardiasis, but does not have any diarrhea. My health care provider says treatment is not necessary. Is this true?

In general, the answer supported by the American Academy of Pediatrics is that treatment is not necessary. However, there are a few exceptions. If your child does not have diarrhea, but is having nausea, or is fatigued, losing weight, or has a poor appetite, you and your health care provider may wish to consider treatment. If your child attends a day care center where an outbreak is continuing to occur despite efforts to control it, screening and treatment of children without obvious symptoms may be a good idea. The same is true if several family members are ill, or if a family member is pregnant and therefore not able to take the most effective anti-Giardia medications.

For more information:

  1. Addiss DG, Juranek DD, Spencer HC. Treatment of children with asymptomatic and nondiarrheal Giardia infection. Pediatr Infect Dis J 1991;10:843-6.

  2. Addiss DG, Davis JP, Roberts JM, Mast EE. Epidemiology of giardiasis in Wisconsin. Increasing incidence of reported cases and unexplained seasonal trends. Am J Trop Med Hyg 1992;47:13-9.

  3. Bartlett AV, Englander SJ, Jarvis BA, Ludwig L, Carlson JF, Topping JP. Controlled trial of Giardia lamblia: Control strategies in day care centers. Am J Public Health 1991;81:1001-6.

  4. Kreuter AK, Del Bene VE, Amstey MS. Giardiasis in pregnancy. Am J Obstet Gynecol 1981;40:895-901.

  5. Lengerich EJ, Addiss DG, Juranek DD. Severe giardiasis in the United States. Clin Infect Dis 1994; 18:760-3.

  6. Steketee RW, Reid S, Cheng T, et al. Recurrent outbreaks of giardiasis in a child day care center, Wisconsin. Am J Public Health 1989;79:485-90.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

Division of Parasitic Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention

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