Giardiasis is an intestinal illness caused by a microscopic parasite called Giardia lamblia.
You can become infected by drinking water or eating food that is contaminated with the parasite. You can also become sick by touching stool or objects contaminated by stool, and then touching your mouth with unwashed hands. Person-to-person transmission can occur in day care centers or other settings where hand-washing practices are poor. Sexual practices that result in hand or mouth contact with stool can also spread the infection.
Giardiasis occurs more often in children and child care workers, people who travel to areas with poor food or water sanitation, men who have sex with men and those who drink water from sources such as lakes, rivers or streams.
Symptoms usually begin within 10 days after exposure, but the range can be from three to 25 days. In some cases, there are no symptoms at all. Fever is rarely present. Occasionally, chronic diarrhea can develop over several weeks or months, with significant weight loss. In otherwise healthy people, symptoms can last two to six weeks.
Once infected, you can carry and shed the parasite for a few weeks to a few months. Treatment with some medicines may shorten this carrier period.
Health care providers can detect the infection through stool tests.
People with giardiasis should drink plenty of fluids, especially young children and pregnant women. Healthy people usually recover on their own without medication. Medicines for treatment such as metronidazole, tinidazole or nitazoxanide can be prescribed by a health care provider.
Since the Giardia parasite is found in the stool, people should stay home from work, school or child care if they cannot control their bowel movements. That includes infants, young children and people with certain types of disabilities.
Food handlers, health care workers and children in day care must get approval from the Health Department before they can return to work or school. This involves follow-up stool testing.