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What is giardiasis?

Giardiasis is an infectious diarrheal disease caused by the parasite Giardia intestinalis (also known as Giardia lamblia or Giardia duodenalis ), which can be transmitted through oral-fecal contact and by water contaminated by feces. Travelers are cautioned against drinking any untreated water.

According to the Centers for Disease Control and Prevention (CDC), Giardia intestinalis is one of the most common intestinal parasites in the world. It is most prevalent in developing countries, where infections are associated with poor sanitary conditions, poor water quality control, and overcrowding. However, giardia is also the most common cause of parasitic infection in the US.

Giardia intestinalis is a major cause of waterborne outbreaks of diarrhea in the United States. It occurs primarily in areas where water supplies have become contaminated with feces from humans or, possibly, from animals (e.g., cats, dogs, cattle, deer, and beavers). Outbreaks have occurred throughout the country.

What causes giardiasis?

The Giardia intestinalis parasite lives in two stages:

  • trophozoites – the active form inside the body
  • cysts – the resting stage that enables the parasite to survive outside the body

Infection begins when the cysts are consumed through food or water. Stomach acid activates the cysts and the trophozoites are released. They become attached to the lining of the small intestine and reproduce. Cysts form in the lower intestines and are then passed in the feces.

The parasite may be directly transmitted from person to person by contact with infected feces, or indirectly, through consuming food and water contaminated with cyst-containing feces.

Treatment for giardiasis:

Giardiasis may be treated with medications prescribed by a physician. Specific treatment for giardiasis will be determined by your physician based on:

  • your overall health and medical history
  • extent of the disease
  • your tolerance for specific medications, procedures, or therapies
  • expectations for the course of the disease