Often no symptoms are present. Sudden diarrhea and abdominal cramping. Some persons have only mild diarrhea and indigestion. Loose, bulky, bad-smelling stools. Occasionally persistent symptoms over weeks and months.
Giardia parasites enter the body through food or water and multiply in the small intestine.
Local inflammation, causing diarrhea and other symptoms, occurs in 1 to 3 weeks. Drinking stream water while camping. Previous stomach surgery. Stomach acid normally provides some protection against this infection. Oral-anal sexual practices.