An infection or parasitic disease produced by the bacteria Leptospira. Weil disease is a severe form of Leptospirosis that is characterized by severe dysfunction of the liver and kidneys. The infection causes excessive bleeding within the body and is potentially fatal. It is contracted by ingesting or swimming in water contaminated with the infected urine of wild and domestic animals (rats, cats, dogs) who shed the bacteria in their urine. Treatment consists of administering penicillins, tetracyclines, chloramphenicol, or erythromycin.