What is giardiasis?

Giardiasis (say "jee-ar-DYE-uh-sus") is an infection of the intestines caused by the parasite Giardia lamblia.

The illness, also called giardia (say "jee-AR-dee-uh"), is most often a problem in undeveloped countries where tap water is not safe.

How can you become infected with giardia?

You may become infected with giardia if you eat food or drink water that is tainted with human or animal waste. In the United States and Canada, you can get giardia by drinking untreated water from wells, streams, rivers, and lakes. This is true even in mountain lakes and streams where the water may seem very pure.

You can get giardia from someone else through:

• Close contact with someone who is infected.
• Working in day care centers for young children. For example, if you change a diaper and don't wash your hands afterward, anything or anyone you touch could get infected. You could even get the illness yourself if you touch your mouth or eat food that you've touched. Children in day care centers are also more likely to get infected.
• Working or living in nursing homes or other care centers where people may have poor bowel control and poor hygiene.
• Some types of sexual contact, such as anal-oral contact.

What are the symptoms?

Giardia can cause diarrhea, stomach cramps, gas, and nausea. You may feel sick once and then get better. Or your symptoms may come and go for some time. Some children with giardiasis do not grow or gain weight normally. Sometimes giardiasis does not cause any symptoms.

After a person is exposed to the parasite, it usually takes 7 to 10 days for the infection to develop, but it can take from 3 to 25 days or longer. You can pass the infection to others during the entire time you are infected. You may be infected for months, even if you don't have symptoms.

How is it diagnosed?

Your doctor will ask questions about your past health and will do a physical exam to find out if you have giardiasis. He or she may also test your stool for the parasite that causes the infection.

How is it treated?

Your doctor may prescribe medicine to kill the parasite. Treatment also lowers the chance that you will pass giardia to others. Taking all the medicine is important so the infection does not come back.

In some situations, you may be tested for giardiasis even though you don't have any symptoms. For example, this could happen during an outbreak at a day care center. If tests show that you are infected, doctors recommend that you get treatment even if you don't have symptoms. This is because a small number of people who are not treated get a long-term infection.