Giardiasis (popularly known as beaver fever) is a zoonotic parasitic disease caused by the flagellate protozoan Giardia lamblia (also sometimes called Giardia intestinalis and Giardia duodenalis). The giardia organism inhabits the digestive tract of a wide variety of domestic and wild animal species, as well as humans. It is one of the most common pathogenic parasitic infections in humans worldwide; in 2013, there were about 280 million people worldwide with symptomatic giardiasis.