Giardia Lamblia

Giardia lamblia, also known scientifically as Giardia duodenalis or Giardia intestinalis, is a flagellated single-celled parasite that colonizes the small intestine and causes the diarrheal illness giardiasis. It attaches to the intestinal lining using a disc-shaped sucker on its underside and does not invade deeper tissue, remaining confined to the intestinal lumen; when stained for microscopic examination it has a distinctive appearance often described as resembling a smiley face. It exists in an active, feeding form and a dormant, protective cyst form, and it spreads mainly through contaminated drinking water, food, soil or sewage, making it especially common where water treatment is inadequate.