Diseases & Conditions
The most common cause of waterborne infection in the United States, this infection of the small intestine is caused by a protozoon found in the human intestinal tract and in feces. In recent years, outbreaks of giardiasis have been common among preschool children and in large public picnic areas. Giardia can easily be spread in the child’s home, and parents and siblings may become infected.
Giardiasis is caused by Giardia lamblia, a type of protozoa found in the human intestinal tract and in feces. It causes foul-smelling, explosive diarrhea. The protozoa was named for the 19th-century French biologist Alfred Giard, who discovered it.
The protozoa are spread by contaminated food or water, or by direct personal hand-to-mouth contact. Children can spread the infection by touching contaminated toys, changing tables, utensils, or their own feces. For this reason, the infection spreads quickly through a day-care center or institution for the developmentally disabled. Unﬁltered streams or lakes that may be contaminated by human feces are a common source of infection to campers. Infection is often spread by not properly washing hands after bowel movements, after changing diapers, or before preparing foods. In addition, outbreaks have also been linked to portable wading pools and contaminated water supplies.
The infection interferes with the body’s ability to absorb fats in the intestinal tract, so the stool is ﬁlled with fat. Giardiasis is not fatal, and about two thirds of infected children have no symptoms. When they do occur, symptoms appear about one to three days after infection and include explosive diarrhea, foul-smelling and greasy feces, stomach pains, gas, loss of appetite, nausea, and vomiting. In some cases, the infection can become chronic.
Giardiasis is diagnosed by examining three stool samples for the presence of the parasites. Because the parasite is shed intermittently, half of the infections will be missed if only one specimen gets checked. Stool collection kits are available for this purpose. A different test looks for the proteins of Giardia in the stool sample.
Acute giardiasis usually runs its course and then clears up, but antibiotics will help relieve symptoms and prevent the spread of infection. Medications include metronidazole, furazolidone, and paromomycin. Occasionally, treatment fails; in this case, the patient should wait two weeks and repeat the medication. Anyone with an impaired immune system may need to combine medications. Healthy carriers do not need to be treated.
Some children get a chronic infection and suffer with diarrhea and cramps for long periods of time, losing weight, and growing poorly. Those most at risk for an infection are those with impaired immune function and malnourished children.
While chlorine in water treatment will not kill the cysts, ﬁltered public water supplies eliminate it. It can be prevented by thoroughly washing hands before handling food. In addition, children should:
• maintain good personal hygiene
• not eat unwashed fruit or vegetables unless they can be peeled
• stay home from a child-care center if they have severe diarrhea until the stool returns to normal.