Glossary

Leptospirosis

A bacterial infection spread through the urine of wildlife and contaminated water that can damage a dog's kidneys and liver, and can infect people.

Also called: lepto, leptospira, rat fever in dogs, Weil's disease

Leptospirosis is caused by Leptospira bacteria, which are shed in the urine of infected animals such as rats, raccoons, opossums and livestock. Dogs catch it by drinking from or swimming in puddles, ponds and slow water, or from soil, even in city backyards. Signs include fever, vomiting, tiredness, increased drinking and urination and yellow gums, and kidney or liver failure can follow.

It is a zoonosis, meaning people can catch it from infected urine, so a vet will advise on hygiene around a sick dog. A vaccine exists. Guidelines differ: AAHA recommends it for all dogs, while WSAVA calls it core only where the disease is common. Ask a veterinarian about your area and your dog's lifestyle.

Any dog with these signs needs a veterinarian quickly, because early care improves recovery.

Last reviewed November 8, 2026

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Related terms

Core vaccines The vaccines veterinary guidelines recommend for virtually every dog, protecting against distemper, parvovirus, canine adenovirus and rabies. Non-core vaccines Vaccines given only to dogs whose lifestyle, location or travel puts them at risk, such as Bordetella, Lyme and canine influenza. DHPP vaccine The standard combination puppy and adult shot covering distemper, hepatitis (adenovirus), parainfluenza and parvovirus.