Leptospirosis is a disease caused by a spiral shaped bacteria called leptospires. It occurs worldwide and can infect humans as well as wild and domestic animals, including dogs. In dogs, leptospirosis can cause both acute and chronic disease, especially of the liver and kidneys. Clinical signs of leptospirosis may include: decreased appetite, vomiting, diarrhea, muscle pain, increased thirst and urination, or jaundice (yellowing of the skin).

The leptospira bacteria are spread through the urine of infected animals, which can then travel through water or soil and survive for weeks or months. Wild animal populations (raccoons, skunks, squirrels, voles, deer, and opossum) serve as reservoirs of infection that can contaminate the environment. A dog typically becomes infected indirectly by drinking water contaminated by the urine of an infected animal. Leptospira can also be transmitted through direct contact with Leptospira -infected urine, bite wounds, and through ingestion of the bacteria. There also seems to be an increased risk of exposure during years of frequent flooding, and in the late summer and fall. Humans can become infected through contact with infected urine