This book deals with research into the occurrence of leptospirosis in buffaloes destined for slaughter, but reared extensively on rural properties in municipalities in the Arari micro-region, Maraj? Archipelago, in the state of Par?, Brazil. The work reports on the presence of leptospires in kidney, urine and blood serum samples from buffaloes collected at a slaughterhouse. The study used a serological diagnostic method to determine the prevalence of leptospirosis in these animals, and to demonstrate the renal carrier status of the Marajoara buffalo, culture media and molecular biology using the Polymerase Chain Reaction technique were used in renal and urinary samples. This book is dedicated to all readers interested in studies relating to biology, microbiology, epidemiology, sanitary defense and public health.