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Giardia: What Is Giardiasis?

  • Giardiasis is the name of the disease caused by Giardia lamblia parasites that infect the small bowel.
  • Giardiasis is caused by Giardialamblia parasites that damage the small intestine; Giardia lamblia forms cysts are transmitted to humans in contaminated water or food and by person-to-person contact.
  • Symptoms of giardiasis are variable; some people have no symptoms but still pass cysts in the stool and are considered carriers of the parasite while others may develop acute or chronic diarrheal illnesses that begin to show symptoms in one to two weeks after swallowing cysts.
  • Symptoms of acute giardiasis are profuse watery diarrhea that later becomes greasy and foul-smelling with occasional bloating, abdominal cramping, and passing gas (flatulence).
  • Chronic diarrheal illness symptoms include greasy, foul-smelling, yellowish diarrhea, weight loss, and abdominal pain.
  • Seek medical care if you suspect you have giardiasis; if a person develops profuse watery diarrhea with dehydration or is passing many small volume stools that contain blood or mucus, have fever greater than 100.4 F or 38 C, severe abdominal pain and/or diarrhea in individuals older than 70 years or in individuals with weakened immune systems, the person should go to an urgent care clinic or an emergency department for evaluation.
  • Giardiasis may be diagnosed by several different types of tests including examining the stool cysts, detection of antigens (substances the the immune system thinks are foreign or dangerous) in the stool, a string test (patients swallow a string taped to their cheek), and for more difficult diagnoses, aspiration of small bowel contents or biopsy of the small bowel may be done.
  • Some individuals may be treated at home with fluids to prevent dehydration, bland foods and avoiding milk for several weeks; however, this may not be appropriate treatment for others so you should consult your health-care professional before home treatment.
  • Treatment for Giardiasis is mainly done by medicines, the most common treatment is Tinidazole (Tindamax) . If you are pregnant, consult your OB/GYN physician to monitor treatments.
  • Follow-up is important to reduce the spread of the disease to caregivers.
  • Giardiasis can be prevented by avoiding contaminated food and water, oral/anal sex, and by practicing excellent handwashing techniques.
  • The prognosis for someone with giardiasis is usually very good although in a few individuals, dehydration and malnutrition (especially young children) may lead to developmental impairment.

Giardia: What Causes Giardiasis?

Giardia lamblia cysts are transmitted to humans in various ways.

  • Contaminated water supplies: Giardia lamblia is one of the most common causes of water-borne diarrhea outbreaks. Sources of contaminated water include public facilities that improperly filter and treat water, water in developing countries, or rivers and lakes used by hikers. Overseas travelers and hikers are at a high risk for infection.
  • Contaminated food: Food that may have been washed in contaminated water, exposed to manure, or prepared by an infected person can transmit the disease.
  • Person-to-person contact: Infection may be caused by poor hygiene and most commonly occurs in daycare centers, nursing homes, and during oral-anal sexual contact. Family members, daycare workers, and others in contact with infected stool may then themselves become infected.
Medically Reviewed by a Doctor on 10/26/2016

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Giardiasis Symptoms

Giardia can cause diarrhea, stomach cramps, gas, and nausea. You may feel sick once and then get better. Or your symptoms may come and go for some time. Some children with giardiasis do not grow or gain weight normally. Sometimes giardiasis does not cause any symptoms.

After a person is exposed to the parasite, it usually takes 7 to 10 days for the infection to develop, but it can take from 3 to 25 days or longer. You can pass the infection to others during the entire time you are infected. You may be infected for months, even if you don't have symptoms.

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Giardia lamblia was originally identified by von Leeuwenhoek in the 1600s and was first recognized in human stool byVilem Dusan Lambl (1824-1895) in 1859and by Alfred Giard (1846-1908) after whom it is named.

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