Leptospirosis: The Puddle-Borne Disease Every Dog Owner Should Know

What it is

Leptospirosis is a bacterial disease spread through the urine of wildlife — raccoons, rodents, deer — often via puddles, ponds, and damp soil. It's on the rise in US cities and suburbs alike, not just farms.

Why it's serious

Lepto attacks the kidneys and liver and can be fatal without fast treatment. It's also zoonotic: infected dogs can pass it to humans. Early signs are vague — fever, vomiting, lethargy, drinking and urinating more — so tell your vet if your dog swims or drinks from puddles.

The vaccine has improved

Older lepto vaccines had a reputation for reactions; modern ones are much cleaner, and many US vets now consider lepto a core vaccine for dogs with any outdoor exposure. It requires an initial two-dose series, then yearly boosters.

Everyday prevention

Discourage puddle-drinking, secure trash to keep wildlife away, and control rodents around your home. If your dog gets sick after swimming or heavy rain, mention it — early antibiotics save lives.