Giardia infection or giardiasis is also known as beaver fever. It is an intestinal tract infection caused by the giardia parasite that affects mammals such as humans, dogs, and cats. When animals unknowingly ingest the giardia parasite's larvae, also called cysts, the result is Giardiasis. These larvae or cysts often live in waterborne sources. The parasite is also spread through ingestion of fecal matter. Giardiasis affects the small intestine and often diarrhea is a major symptom of the infection. This is because the giardia parasite effectively takes over the intestinal wall, leading to an inability of the small intestine to function.