What is giardiasis? 

Giardiasis is an intestinal illness caused by a microscopic parasite called Giardia. It is a fairly common cause of diarrhea throughout the U.S. and the world.

Who gets giardiasis?

Anyone can get giardiasis, but it tends to occur more often in people in daycare centers, international travelers, and individuals who drink improperly treated surface water (such as hikers drinking from a stream or people swallowing water while swimming in a river or lake).

How is giardiasis spread? 

The parasite has to enter the mouth to cause infection. This happens when people and animals infected with Giardia shed the parasite in their feces (stool) and the feces then contaminate surfaces, food, or water. People then can become infected by touching contaminated surfaces, getting the parasite on their hands and then putting their hands in their mouths, or by eating the contaminated food or swallowing the contaminated water.

What are the symptoms of giardiasis? 

People infected with Giardia may have no symptoms at all, or may experience a mild illness or severe diarrhea. Diarrhea can last for several weeks or months, leading to weight loss and dehydration. Gas, greasy stools, and stomach cramps also can occur.

How soon after exposure do symptoms appear? 

Symptoms may appear anywhere from 3 to 25 days after exposure, but usually appear within 7 to 10 days after exposure.

How is giardiasis diagnosed? 

To confirm the diagnosis, a doctor needs to send a sample of your stool to a lab and ask them to test for Giardia. Traditionally labs have examined stool under a microscope to diagnose giardiasis, but some labs now offer other tests. Several stool specimens must be obtained because the number of Giardia parasites found in the stool changes from day to day.

What is the treatment for giardiasis? 

Persons with diarrhea should drink plenty of fluids. Some individuals may recover on their own without medication. Specific medicines may be prescribed by doctors to treat people who are ill with giardiasis.

How can giardiasis be prevented? 

  • Carefully wash hands thoroughly after using the toilet or changing diapers, before and after preparing food, and after being in contact with animals.
  • Avoid drinking improperly treated water.  Filter and boil or disinfect surface water if drinking from those natural water sources is necessary, such as when hiking or camping.
  • Protect public water supplies against contamination with animal or human feces. When camping or otherwise unable to use sanitary facilities, carefully dispose of sewage waste to prevent contamination of outdoor waterways.

How long can an infected person carry Giardia parasites?

Persons may excrete Giardia in their stools from a few weeks to a few months. Treatment may shorten the illness and the time the parasite remains in the stool.

Should an infected person be excluded from work or school? 

People with diarrhea need to be excluded from daycare, patient care, or food handling, where they might present a risk to others. Most people may return to work or school when diarrhea stops, provided that they carefully wash their hands after each toilet visit, after changing diapers, and before preparing food. The health department will give advice on each situation in which the person with giardiasis is a food handler, health care worker, or daycare worker or attendee.

How can I learn more about giardiasis? 


September 2013