Giardiasis is a disease of the small bowel caused by the protozoan parasite Giardia intestinalis (syn.duodenalis or lamblia). Giardia is one of the most common intestinal parasites in the world, and occurs at very high prevalence rates in places with poor water sanitation. Individuals become infected through ingesting or coming into contact with contaminated water, food or soil. It can also be spread through the faecal-oral route due to poor hygiene practices, which makes it common in day-care centers. G. intestinalis lives inside the intestines of infected humans or other animals including cats, dogs, birds, cows, beaver and deer. Symptoms of infection include diarrhea, malaise, excessive gas, bloating, nausea, diminished interest in food, possible vomiting and weight loss.