leptospirosis (also known as weil's disease, canicola fever, canefield fever, nanukayami fever or seven day fever) is a bacterial disease. it is caused by spirochaetes of the genus "leptospira". this bacterium affects humans and many animals, including mammals, birds, amphibians, and reptiles. it was first described by adolf weil in 1886. at the time he reported an "acute infectious disease with enlargement of spleen, jaundice and nephritis". the pathogen, "leptospira"-genus bacteria was isolated in 1907 from a post mortem kidney slice.