Giardiasis is an intestinal infection in humans and animals caused by a microscopic protozoan parasite, Giardia duodenalis. Giardia is a simple one-celled parasitic species; it is not a worm, bacteria, or virus. The Giardia organism has two forms. A fragile feeding form, known as the trophozoite, exists in the gut of infected animals, while a… Read more »