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Classification & external resources
Giardia cell, SEM
ICD-10 A07.1
ICD-9 007.1
DiseasesDB 5213
MedlinePlus 000288
eMedicine emerg/215 
MeSH D005873

Giardiasis (also known as beaver fever) is a disease caused by the flagellate protozoan Giardia lamblia (also sometimes called Giardia intestinalis and Giardia duodenalis) [1]. The giardia organism inhabits the digestive tract of a wide variety of domestic and wild animal species, including humans. It is a common cause of gastroenteritis in humans, infecting approximately 200 million people worldwide.



Giardiasis is passed via the fecal-oral route. Primary routes are personal contact and contaminated water and food. People who spend time in institutional or day-care environments are more susceptible, as are travelers and those who consume improperly treated water. It is a particular danger to people hiking or backpacking in wilderness areas worldwide. Giardia is suspected to be zoonotic—communicable between animals and humans. Major reservoir hosts would include beavers, dogs, cats, horses, and cattle.


Symptoms include loss of appetite, lethargy, fever, explosive diarrhea, loose or watery stool, stomach cramps, upset stomach, projectile vomiting (uncommon), bloating, and flatulence. Symptoms typically begin 1–2 weeks after infection and may wane and reappear cyclically. Symptoms are caused largely by the thick coating of Giardia organisms coating the inside of the small intestine and blocking nutrient absorption. Most people are asymptomatic; only about a third of infected people exhibit symptoms. Untreated, symptoms may last for six weeks or longer.


Drugs used to treat adults include metronidazole, albendazole and quinacrine. Furazolidone and nitazoxanide may be used in children. Treatment is not always necessary, as the body can defeat the infection by itself.

The drug tinidazole can treat giardiasis in a single treatment of 2000 mg, instead of the longer treatment of the other medications listed. The shorter duration of treatment may also cause less patient distress. Tinidazole is now approved by the FDA[2] and available to U.S. patients.

The supplement barberry (Berberis vulgaris) can also be helpful in treating Giardiasis.[3][4]

Lab Diagnosis

  • The mainstay of diagnosis of Giardiasis is stool microscopy. This can be for motile trophozoites or for the distinctive oval G.lamblia cysts.
  • The entero-test uses a gelatin capsule with an attached thread. One end is attached to the inner aspect of the patient's cheek, and the capsule is swallowed. Later the thread is withdrawn and shaken in saline to release trophozoites which can be detected microscopically.
  • A new immunologic test referred to as ELISA, for enzyme-linked immunosorbent assay is now available. These tests are capable of a 90 percent detection rate or more.[5]


  1. ^ Huang, White. An Updated Review on Cryptosporidium and Giardia Gastroenterol Clin N Am 35 (2006) 291–314
  2. ^ FDA info on Tindamax.
  3. ^ List of natural supplements, retrieved Feb. 7, 2007
  4. ^ [1]
  5. ^ Giardia Lamblia and Giardiasis by Robert L. Rockwell, PhD
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Giardiasis". A list of authors is available in Wikipedia.
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