About Giardiasis

Giardiasis is a diarrheal illness caused by Giardia intestinalis (also known as Giardia lamblia or Giardia duodenalis), a one-celled, microscopic protozoan parasite.

The parasite is passed in the stool of an infected person or animal. The parasite is protected by an outer shell that allows it to survive outside the body and in the environment for long periods of time.

On this page:
Fact sheet
Transmission
Symptoms
Diagnosis
Treatment
Prevention
Control measures

Fact sheet

• Giardiasis Fact Sheet
  Answers to frequently asked questions about Giardia.

Transmission

Giardia lives in the intestine of infected humans or animals. Millions of germs can be released in a bowel movement from an infected human or animal. You can become infected after accidentally ingesting the parasite.

Giardia may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals.

Common ways Giardia is transmitted include:

• Swallowing contaminated water while swimming or drinking.
• Having contact with people who are sick with giardiasis, especially in child care settings.
• Swallowing Giardia organisms picked up from contaminated surfaces, like changing tables, door handles, and toys.
• Eating foods contaminated with the parasite.
• Exposure to fecal material during sexual activity.

Symptoms

Common symptoms include:

• Diarrhea
• Greasy stools that can float
• Gas and bloating
• Stomach cramps
• Loss of appetite
• Weight loss
• Slight fever

Some people have no symptoms.

Symptoms generally begin 1 to 3 weeks after exposure and last about 2 to 6 weeks in healthy persons.

Diagnosis

Giardiasis is typically diagnosed by testing a stool (poop) specimen for the parasite. Your health care provider may ask you to submit up to three stool specimens collected at least 24 hours apart to increase the chance that Giardia is detected in your stool.

Treatment

Giardiasis can be treated with a number of prescription drugs including metronidazole, nitazoxanide, and tinidazole. Some infections are self-limited, and treatment is not required. Diarrhea should be managed by drinking plenty of fluids to prevent dehydration.

If you or your child test positive for Giardia and have no symptoms, treatment is generally not recommended.

Prevention

You can minimize your risk of getting giardiasis by following these recommendations:

• Wash hands after using the bathroom and changing diapers, and before handling or eating any food.
• Do not swallow water while swimming.
• Use caution when traveling in countries with minimal water treatment and sanitation systems by avoiding tap water, fountain drinks, ice, and raw foods.
  • Food and Water Safety for Travelers
    CDC; Contains information about food and water safety for travelers, especially people traveling to developing countries. 
• Do not drink untreated water from lakes, rivers, springs, ponds, and streams. If you are unable to avoid drinking water that might be contaminated, learn how to treat your water properly.
  • Preventing Illness while Camping, Hiking, and Traveling
    Information about different methods that can be used to treat drinking water.
• Reduce fecal-oral exposure during sexual activity and avoid sexual activity with those who have diarrhea or who recently recovered from giardiasis.

Control measures

People who have symptoms of giardiasis can reduce the risk of spreading their illness to others by following these recommendations:

• Wash hands carefully and frequently with soap, especially after using the bathroom and changing diapers, and before handling or eating any food.
  • This is particularly important in child care/preschool settings, where many outbreaks have occurred due to person-to-person spread.
• Stay out of pools, splash pads, and lakes while sick.
• Do not bathe with others while sick.
• Do not attend or work at a child care or preschool until 24 hours after diarrhea stops.
  • Specific Disease Exclusion Guidelines for Child Care and Preschool
    Children and adults are subject to certain restrictions from child care/preschool when they are sick with a diarrheal illness.
• Wait to have sex until symptoms have stopped.

Do you suspect that you have a foodborne or waterborne illness? Visit reporting suspected foodborne/waterborne illnesses.