Giardiasis

• Giardiasis [gee-are-DI-uh-sis] is a parasitic infection of the small intestine.
• People get giardiasis when they swallow water or food contaminated with stool from an infected person or animal. People also get giardiasis from hand-to-mouth contact with contaminated surfaces or objects.
• Persons most at risk for giardiasis are children and staff at day-care centers and persons who drink untreated water when traveling or camping.
• To prevent giardiasis: 1) wash hands often, 2) avoid water or food that might be contaminated with stool, and 3) when camping or hiking, always boil, filter, or chemically treat surface water before drinking.

What is giardiasis?

Giardiasis is an infection of the intestine that can cause diarrhea.

What is the infectious agent that causes giardiasis?

Giardiasis is caused by Giardia lamblia, a one-celled, microscopic parasite that lives in the intestines of people and animals. Infected people and animals pass Giardia cysts in their stool. Giardia cysts can survive in the environment in water and food and on surfaces and objects.

Where is giardiasis found?

The Giardia parasite is found in every region of the United States and throughout the world. Giardiasis occurs often in mountainous areas where water supplies from lakes, ponds, or streams have become contaminated with animal droppings or human waste.

How do people get giardiasis?

People get giardiasis by swallowing Giardia cysts, the infectious stage of the parasite. People can get giardiasis by:

• Putting anything into the mouth that has touched the stool of a person or animal with giardiasis
• Swallowing water (such as from a swimming pool, lake, river, pond, or stream) contaminated with sewage or stool from Giardia-infected people or animals.
• Eating uncooked or undercooked food contaminated with Giardia cysts
• Touching and bringing to the mouth cysts picked up from surfaces (such as toys, bathroom fixtures, changing tables, diaper pails) contaminated with stool from an infected person

What are the signs and symptoms of giardiasis?

The signs and symptoms of giardiasis are similar to those of other intestinal illnesses:

• Diarrhea
• Abdominal cramps
• Nausea

These symptoms can lead to weight loss and dehydration (loss of fluids). However, not all infected persons have symptoms.

How soon after exposure do symptoms appear?

Symptoms usually appear 1 to 2 weeks after infection with the parasite. In otherwise healthy persons, symptoms can last 4 to 6 weeks. Occasionally, symptoms last longer.

How is giardiasis diagnosed?

Giardiasis is diagnosed by examining a stool sample under a microscope to look for Giardia cysts. Because a stool sample might contain only a few cysts, and they can be easy to miss, diagnosis sometimes requires several tests over several days.

Who is at risk for giardiasis?

Anyone can get giardiasis, but some persons are at increased risk:

• Child-care workers
• Diaper-aged children who attend day-care centers
• Persons who travel to countries where the water and food may be contaminated with Giardia
• Hikers, campers, and others who drink unfiltered and untreated water from contaminated sources

Several community-wide outbreaks of giardiasis have been linked to drinking municipal water contaminated with Giardia.

What complications can result from giardiasis?

The parasite lodges in the upper intestine and can be hard to get rid of, so diarrhea can last for several weeks or months and cause weakness and weight loss. Dehydration can be a serious problem for children.

What is the treatment for giardiasis?

Several prescription medicines are available to treat giardiasis. People with severe diarrhea should drink plenty of liquids to prevent dehydration.

How common is giardiasis?

Giardia parasites are among the most common intestinal parasites is the world. Giardiasis can be caught anywhere and is the most common source of chronic diarrhea picked up while traveling. In the United States, Giardia is one of the leading causes of waterborne outbreaks of diarrhea.

Is giardiasis an emerging infectious disease?

Yes. During the past 15 years, Giardia has become recognized as one of the most common causes of waterborne disease in humans in the United States.

How can giardiasis be prevented?

There is no drug to prevent giardiasis. To decrease your risk, follow these steps:

• Wash hands thoroughly with soap and water after toilet visits, after changing diapers, before preparing food or drink, and before eating.
• Avoid water or food that might be contaminated.
• Carefully dispose of sewage waste so as not to contaminate surface water or groundwater.
• Practice good hygiene with diapered children in day-care centers. Wash hands thoroughly with plenty of soap and warm water after every diaper change, even if wearing gloves.
• Keep children with diarrhea at home from day-care centers.
• Avoid swimming pools if you have giardiasis. Giardia cysts are resistant to chlorine levels used in swimming pools and are passed in the stools of infected people for several weeks after they no longer have symptoms.
• During community-wide outbreaks caused by contaminated drinking water, boil drinking water for 1 minute to kill the Giardia parasite and make the water safe to drink.

When visiting a wilderness area or country where the water supply might be unsafe, follow these water-safety precautions:

• Do not drink untreated or inadequately filtered surface water. Never drink water directly from lakes, streams, reservoirs, or rivers without boiling or treating it first. Even crystal-clear water in wilderness areas can be contaminated.
• Avoid drinking unboiled tap water. Bottled or canned carbonated beverages, seltzers, or pasteurized fruit drinks, and steaming hot coffee and tea are safe to drink. Check the label on bottled water to make sure it has been properly filtered.
• Avoid ice and beverages made from water that might not be adequately treated.
• Do not eat uncooked or unpeeled fruits or vegetables that were grown locally or that were washed in or touched by contaminated water.
• Avoid swallowing water when swimming, especially in lakes, ponds, and rivers that are open to contamination by human or animal wastes.

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.

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