What is giardiasis?

Giardiasis is an infection caused by a parasite called Giardia lamblia. Giardiasis has a worldwide distribution and is a common cause of diarrhea in the United States.

Who gets giardiasis?

Anyone can get giardiasis, but children are infected more frequently than adults. Persons who drink untreated water also are at greater risk of becoming infected with Giardia.

Where are Giardia organisms found?

  • Humans are the main host of Giardia, but Giardia cysts can also be found in:
    • Dogs
    • Beavers
    • Other domestic and wild animals
  • Giardia cysts are also found in lakes and streams contaminated with feces from an infected animal or human.
  • Giardia may also be present in areas of poor sanitation, and child care centers with children who are not toilet trained.

How is giardiasis spread?

  • Giardia is passed in the feces of an infected person or animal and may contaminate food or water.
  • The disease can spread from person-to-person in child care centers, especially those that care for children who are not toilet trained.
  • Backpackers, campers and hunters may get giardiasis by drinking directly from lakes or streams, even though the water may appear very clean.

What are the symptoms of giardiasis?

The most common symptoms of giardiasis include:

  • Mild or severe diarrhea with loose and pale greasy stools
  • Stomach cramps
  • Bloating
  • Weight loss
  • Fatigue
  • Fever is rare

Some people may not become ill, but may still transmit their infection.

Young children often have no symptoms. (Children in child care centers may often be infected, but do not need treatment unless they get diarrhea.)

How soon do symptoms appear?

Diarrhea usually begins within seven to 10 days, but may be as early as five days or as late as 25 days after infection with Giardia.

How long can an infected person spread Giardia?

The disease can be spread as long as the infected person excretes cysts. Treatment may shorten length of time.

What is the treatment for giardiasis?

Anti-parasitic medication is often given to treat giardiasis. Some people recover without treatment.

Does everyone infected with giardia need to be treated?


Should an infected person be excluded from work or school?

  • Children with diarrhea should not attend a child care facility. They may return when diarrhea stops.
  • Food handlers and child care workers who have giardiasis must test negative for Giardia lamblia cysts before returning to work.

What can be done to stop the spread of giardiasis?

Some general guidelines are:

  • Carefully wash hands after using the toilet or changing diapers.
  • Dispose of sewage properly so water sources will not be infected.
  • Do not drink water that has not been properly treated.
    • When camping, boil your water before drinking.

Where can I get more information?

Contact your doctor or the Southern Nevada Health District, Office of Epidemiology at (702) 759-1300.

Contact Information

(702) 759-1000

Updated on: August 17, 2018

Skip to content