Giardiasis - Epidemiology

What is giardiasis?

Giardiasis is a diarrheal illness caused by a microscopic parasite called Giardia. It is a fairly common cause of diarrhea throughout the United States and the world.

Who gets giardiasis?

Anyone can get giardiasis, but it tends to occur more often in people in child care centers, international travelers, and persons 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 Giardia parasite can be found in the feces (stool) of infected people and animals (such as cats, dogs, deer, cattle, and beavers), and their feces can contaminate surfaces, food, or water. People get sick by swallowing the contaminated food or water or by putting their hands in their mouths after touching contaminated surfaces (such as toys, diaper pails, etc.).

What are the symptoms of giardiasis?

Some people infected with Giardia have no symptoms at all; others experience mild to severe intestinal symptoms. Diarrhea can last for several weeks or months, leading to weight loss and dehydration. Symptoms of gas, greasy stools, and stomach cramps might also occur.

How soon after exposure do symptoms appear?

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

How is giardiasis diagnosed?

To confirm the diagnosis, a stool sample should be collected and tested at a laboratory. Several stool specimens must be obtained over several days because the number of Giardia parasites found in the stool changes from day to day.

What is the treatment for giardiasis?

It is very important for people with giardiasis to drink plenty of fluids. Dehydration, from losing too much fluid, can occur with giardiasis and is especially a risk for infants and pregnant women. Consult with your healthcare provider when the illness begins. Prescription medicines are sometimes recommended to treat this illness.

How can giardiasis be prevented?

Carefully wash hands with soap and water 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 natural water sources, such as when hiking or camping.
Protect all 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.
Prevent contact and contamination with feces (stool) during sex.

How long can an infected person carry Giardia parasites?

Persons can excrete Giardia in their stools for a few weeks to a few months. Treatment can 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 child care, patient care, or food handling, where they might pose a risk to others. Most people may return to work or school when diarrhea stops, provided that they carefully wash their hands with soap and water after each toilet visit, after changing diapers, and before preparing food. The health department will give specific advice on each situation in which the infected person is a food handler, health care worker, or child care worker or attendee.

How can I learn more about giardiasis?

If you have concerns about giardiasis, contact your healthcare provider.
Call your local health department. A directory of local health departments is located at the VDH Local Health Districts page.
Visit the Centers for Disease Control and Prevention website at the CDC page on Giardia.