Researches on Leptospirosis ballum

Summary A case of an accidental human infection caused byLeptospira ballum, following a superficial scratch on a finger of the patient while handling a white mouse is described. This mouse proved to be a urinary carrier ofLeptospira ballum.Further investigations revealed that practically all mice of the same colony voidedLeptospira ballum with the urine.On examination of other mice-breeding colonies another colony infected withL. ballum was detected; in 1941 a strain which later also proved to beL. ballum, was isolated from the urine of a white mouse.The various strains were analysed; they were serologically identical toBorg Petersen's type strain although the virulence for guinea-pigs was much less.Mice from aL. ballum-positive colony proved to have no immunity to infection with virulentL. icterohaemorrhagiae, but — with one exception — remained alive and became carriers ofL. icterohaemorrhagiae, whilstL. ballum could not be detected any more in the urine of these mice.