A: Leptospirosis, or "lepto," is a bacterial disease spread through water contaminated by wildlife and domestic animals. Dogs typically contract the disease by drinking or swimming in water in which other animals, such as rats and raccoons, have urinated. Every dog that shares an environment with wild or domestic animals is at risk for contracting leptospirosis and transmitting it to other dogs, and dogs that spend more time outdoors or in areas affected by flooding are at greater risk of contracting leptospirosis.