"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."

Remember, bears do their thing in the woods, but beavers do it in the water.