What is giardiasis?

Giardiasis is a diarrheal illness of the small intestine. It is fairly common among children and travelers. It is caused by the parasite, Giardia intestinalis. A parasite is an organism that is dependent on another organism to survive. Giardiasis is spread by the contamination of food or water, or by person-to-person contact.

Who gets giardiasis?

  • Travelers to countries with poor sanitation
  • People in close contact settings (notably childcare centers)
  • Those in close contact with someone who has the disease
  • People who drink untreated water
  • People who come in close contact with animal feces
  • People who come into contact with feces during sex

What are the symptoms of giardiasis?

  • Mild to severe watery diarrhea
  • Fever
  • Chills
  • Nausea
  • Abdominal pain
  • Bloating
  • Weight loss

How soon do symptoms appear?

Symptoms can appear anywhere from 3 to 25 days after exposure; 10 days after exposure is most common.

How is giardiasis spread?

Giardiasis is spread by the contact of infectious feces of humans and animals. Contaminated food and water contain cysts (or hard shells containing giardia). Cysts are immediately infectious when swallowed. In the United States, the disease is most often spread in close contact settings when hands are not properly washed and from contaminated water.

How common is giardiasis?

Giardiasis is common throughout the world, but is more common in countries where there is poor sanitation. It is the most common protozoan (group of tiny organisms) illness reported in the United States. Many campers and hikers who drink from unsanitary rivers report getting giardiasis. About 33% of people in underdeveloped countries get this illness.

How is giardiasis diagnosed?

To diagnose giardiasis, doctors may take several stool samples and send them off to a lab. The lab tests for Giardia parasites in the stool or by doing a more sensitive test called the Enzyme-Linked ImmunoSorbentAssay (ELISA). If the illness is bad enough, a doctor may take a sample of the lining of the small intestine with an endoscope (a slender medical tool), in a procedure called endoscopy.

How is giardiasis treated?

Giardiasis may be treated by taking prescription medicines. The most common prescription drugs prescribed for giardiasis are metronidazole (Flagyl), tinidazole (Tindamax), and nitazoxanide (Alinia). The medicine will kill off the protozoan organism.

Treatment usually takes 5 to 7 days. It is important that every prescribed pill is taken. Although most patients will respond to one course of the medicine, it is not uncommon for a patient to require another course if the response is not complete.

How do you prevent giardiasis?

  • Practice good hygiene: Wash hands often with soap and clean running water for 20 seconds, especially before and after eating, after using the toilet, and after coming in contact with your own or someone else's germs.
  • Do not drink water that may be contaminated: Do not drink untreated water from pools, lakes, rivers, ponds, and so on. If there is even a slight chance the water may be contaminated, either drink bottled water or boil the water for 5 minutes.
  • Avoid eating food that may be contaminated: Wash all fruits and vegetables thoroughly under hot water. Do not eat raw or undercooked meats, especially in underdeveloped countries where the water and food may be contaminated. Drink bottled water when in underdeveloped countries.
  • Prevent contact with feces during sex: Practice safe sex, especially using protection during oral-anal sex, and wash hands immediately after.
  • Clean up after sick pets: Use gloves and dispose of pet feces in a plastic bag and put it in the garbage. After, wipe up the infected area with hot steaming water and a strong disinfectant. Wash anything that may have been contaminated in the washer with detergent and hot water.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 11/7/2016…#15238