[Alfred Giard, Fr. biologist, 1846-1908]
A genus of protozoa possessing flagella. They inhabit the small intestine of humans and other animals, are pear shaped, and have two nuclei and four pairs of flagella. They attach themselves to the cells of the intestinal mucosa, from which they absorb nourishment. Cysts can survive in water for up to 3 months. The concentration of chlorine routinely used in treating domestic water supplies does not kill Giardia cysts, but boiling water inactivates them.
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