What causes Giardiasis?

Giardiasis is caused by a tiny parasite called Giardia lamblia . Giardia cysts are a resistant form of the parasite that can survive outside a human or animal body. These cysts cause the spread of this disease. For infection to occur, a person must ingest Giardia cysts by mouth. Once cysts are ingested, the parasites start growing and multiplying in the small intestine. Ingesting as few as ten parasitic cysts can cause an infection.

Giardiasis can be contracted by:

• Contact with feces containing the parasitic cysts. Infected feces can be:
  • Human
  • Animal (less often), including beavers, cats, dogs, and cows
• Eating food, drinking water, or swimming in water contaminated by the parasitic cysts
• Contact with a person's hands that are contaminated with parasite cyst-infected stool