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Giardiasis In Children


This is an inflammatory, intestinal condition caused by overgrowth of the protozoan Giardia lamblia. The source of infection is usually untreated water contaminated with G. lamblia cysts.


Giardia lamblia is the most common pathogenic parasite in the U.S. and perhaps the world. Infection with this flagellated protozoan can lead to severe and disabling gastrointestinal symptoms.

Unfiltered stream and lake water that is open to contamination by human feces are a common source of infection to campers and travelers. The symptoms are abdominal discomfort with passage of lots of gas and stools that are foul in odor and float to the top of the toilet bowl.

Chlorine used in water treatment will not kill Giardia cysts, but filtered public water supplies eliminate Giardia.


Giardiasis is spread by fecal-oral routes, either directly between sexual partners, or indirectly via contaminated food or water.

Children who attend childcare centers where there are children in diapers are at highest risk.

Also at risk are campers or hikers who drink from rivers or streams, anyone who drinks unfiltered water, anyone who engages in unprotected anal sex, and travelers to tropical countries who drink inadequately treated water.

In children, the disease is spread by ingesting contaminated feces, usually by hand to mouth contact. The feces of an infected child are filled with Giardia cysts which are infectious.

The cysts are also present on toys, changing tables, and utensils. Many children are not very sick, so they may spread the disease unwittingly. Giardiasis spreads quickly through a child care center or institution for the developmentally delayed.

Those at risk of serious illness are people with weakened immune systems, malnourished children, and individuals with low stomach acid who have had stomach surgery in which part of their stomachs were removed.


Acute giardia infection causes abdominal cramping and diarrhea, both sometimes quite severe.

Some children get chronic giardiasis and have diarrhea and cramps for a long time. Such children lose weight and grow poorly.


A diagnosis is made by looking at a fresh stool specimen to see if the parasite is present.


Several different medicines are available to treat giardiasis.

One is metronidazole (Flagyl). Another is furazolidone (Furoxone), which comes in liquid form and sometimes causes nausea and vomiting. This is rarely used in the U.S.

A third is paromycin (Humatim), which is safe, but not as effective as the other two.

In 90 to 95 percent of patients, giardiasis is cured with quinacrine (Atrabine) hydrochloride or Flagyl. The medicine is taken for seven to ten days.

Occasionally, the treatment fails. If this happens, wait two weeks, then repeat the treatment.

Anyone with a weakened immune system may need to take combinations of more than one medicine.

Preventive measures to be taken include:

  • Frequent washing of the hands, including under the fingernails
  • Not eating unwashed fruits unless peeled
  • Boiling water if there is any doubt about its source
  • Boiling stream or river water for three minutes

If an outbreak of diarrhea occurs in your child care center, notify the health department.