Leptospirosis is a zoonotic disease due to motile Spirochete bacteria. All vertebrates can be infected with pathogenic Leptospira species, such as Leptospira interrogans (L.i) that is responsible for the more severe forms of disease. Different mammals present various disease symptoms and susceptibility, which is puzzling and not understood. For example, rats and mice are asymptomatic renal carriers of leptospires, cattle suffer morbidity and abortions, whereas humans and hamsters can die from acute leptospirosis. Prevalence of leptospirosis is high in tropical and subtropical areas, and in low-income countries with poor sanitation, where seasonal rains and global warming favor the dissemination of leptospires via contaminated sewage. Despite its health and economic burden, leptospirosis is a reemerging neglected disease, but it is not even cited as such by the WHO.