Giardiasis is an intestinal illness caused by a microscopic parasite called Giardia lamblia. It is a common cause of diarrheal illness and over 800 cases are reported in Missouri each year. Cases may occur sporadically or in clusters or outbreaks.

Anyone can get giardiasis but it tends to occur more often in people in institutional settings, children in day care centers, foreign travelers, and individuals who drink improperly treated surface water. Homosexual males may also be at increased risk of getting giardiasis.

The giardia parasite is passed in the stool of an infected person or animal and may contaminate water or food. The parasite is also spread by hand-to-mouth transfer from contaminated body surfaces or objects such as toys or diapering areas. Person to person spread may also occur in day care centers where there is close contact between preschool children who have not yet learned good bathroom and handwashing habits.

Most people with giardiasis will not have any symptoms. Others may have mild to severe diarrhea, cramps, bloating and gas. Occasionally, some will have diarrhea which lasts for several weeks or months,with weight loss.

The symptoms may appear for five to 25 days after exposure but usually within 10 days.

The carrier stage generally lasts from a few weeks to a few months. Treatment with specific medication may shorten the carrier stage.

Giardia has been found in infected people (with or without symptoms) and wild and domestic animals. The beaver has gained attention as a possible source of giardia contamination of lakes, reservoirs and streams, but human fecal wastes are probably just as important.

People with active diarrhea who are unable to control their bowel habits (infants, young children, certain handicapped individuals, for example) may need to be excluded from settings such as day care or group activities where they may present a risk to others. Persons who handle food should not work while diarrhea is present. After they have been treated and the diarrhea has stopped, they may be permitted to return. Individuals who are not in high-risk settings may return to their routine activities when the diarrhea has stopped, provided they carefully wash their hands after each toilet visit.

Medications such as quinacrine, metronidazole or furazolidone are often prescribed by doctors to treat giardiasis. However, some individuals may recover on their own without medication.

Three important preventive measures are:

• Carefully wash hands thoroughly after toilet visits or changing diapers and before preparing or eating foods.
• Carefully dispose of sewage wastes so as not to contaminate surface or ground water.
• Avoid consuming improperly treated drinking water.

March, 1994