Giardiasis is a major diarrheal disease found throughout the world.
Giardiasis is caused by ingestion of Giardia cysts. After ingestion of cysts, excystation, and trophozoite multiplication, colonization of the upper small bowel occurs. The exact pathophysiology of giardiasis is unclear. Postulated mechanisms include damage to the endothelial brush border, enterotoxins, and altered gut motility and fluid hypersecretion via increased adenylate cyclase activity. Most infections result from fecal-oral transmission or ingestion of contaminated water.