Giardia lamblia is a microscopic parasite that causes a gastrointestinal illness called giardiasis.  The main symptom of giardiasis is diarrhea.  Giardia lamblia is often transmitted to children who drink untreated water from creeks and rivers contaminated with the droppings of an infected animal.

What causes giardiasis?

Giardiasis is caused by Giardia lamblia, a microscopic parasite that is found worldwide.  Giardia infect the gastrointestinal tracts of animals, both wild and domestic.  Children may become infected when they are exposed to the stool of an infected child (i.e., by touching unwashed hands) or by exposure to a contaminated water source.

In non-industrialized countries, entire water supplies may become contaminated.  Creeks and lakes may become contaminated with the droppings of an infected wild animal.  A child may become infected after drinking contaminated water while swimming in a mountain lake or from drinking untreated water from a creek while camping.

Giardiasis typically occurs 1 to 4 weeks after exposure to the parasite.

What are the symptoms of giardiasis?

Many infected children and adults will have NO symptoms.  Sometimes the symptoms are severe.

The following symptoms may be present:

• Diarrhea
• Foul-smelling stools
• Excess intestinal gas
• Abdominal bloating
• Loss of appetite
• Weight loss
• Dehydration

How is giardiasis diagnosed?

The diagnosis should be considered in children with profuse, watery diarrhea without fever.  The stools may be extremely foul-smelling.  A child should be tested for giardia if she has been camping in the woods or has been drinking untreated water.

Stools studies (i.e., a sample of poop) can be sent to laboratory.  The parasite may be seen under a microscopic evaluation of the stool sample.  Other more sophisticated tests help with the identification of the parasite in stool sample.

How is giardiasis treated?

Dehydration and abnormal blood electrolyte levels should be corrected.  This is done with appropriate rehydration drinks or with intravenous fluids if necessary.

Metronidazole, an antibiotic an anti-parasitic medicine, is typically given for about a week.  If the infection does not resolve, a second antibiotic course may be needed.

How can giardiasis be avoided?

• Avoid drinking untreated water (i.e., from lakes, streams, creeks, and rivers)
• Don't let children play or drink water from pet water bowls
• Check well-water frequently to make sure it is not contaminated
• Avoid contact with infected children, at least until they begin treatment
• Wash your hands well after changing diapers or playing with children

Illustration - Life cycle of Giardia lamblia (intestinalis), the causal agent of Giardiasis. 2002 CDC. Used with permission.

Photo - ID#: 8698 Description: This scanning electron micrograph (SEM) revealed some of the external ultrastructural details displayed by a flagellated Giardia lamblia protozoan parasite. G. lamblia is the organism responsible for causing the diarrheal disease "giardiasis". Once an animal or person has been infected with this protozoan, the parasite lives in the intestine, and is passed in the stool. Because the parasite is protected by an outer shell, it can survive outside the body, and in the environment for long periods of time. CDC/ Janice Carr. Used with permission.

Photo 2 - Dr. Stan Erlandsen (1988), CDC. Used with permission

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