Often asymptomatic
Most common symptoms include:
Abdominal distension
Colicky abdominal pain
Flatulence
Diarrhea (pale, loose, floating, foul odor)
Borborygmi
No blood or mucus in stool
Sudden onset after incubation period of 1-3 weeks
Symptoms usually resolve in 7-10 days
85% of the time infection resolves spontaneously within 6 weeks
May cause chronic malabsorption-like illness, especially in those with immunoglobulin deficiency
Chronic infections cause weight loss, anemia, lactose intolerance
Abdominal distension
Colicky abdominal pain
Flatulence
Diarrhea (pale, loose, floating, foul odor)
Borborygmi
Giardia lamblia
Viral 
Helicobacter pylori
Bacterial
Balantidium coli
Campylobacter
Clostridium difficile
Shigella