Leptospirosis, often called lepto, is a serious bacterial disease that can be life-threatening for dogs. It can also infect people, though transmission from dogs directly to their owners is rare.
As of early 2026, lepto cases are rising among dogs in the Bay Area and Los Angeles County. Pet guardians can help protect their dogs and their local community by vaccinating their dogs against lepto.
What is leptospirosis?
Lepto is an infection caused by the bacterium Leptospira. There are many different strains, and the bacteria are found worldwide in soil and water. Wildlife, such as rats, raccoons, squirrels, opossums, and deer, can carry Leptospira and shed it in their urine. Infected urine can seep into puddles, creeks, lakes, and even backyard soil.
One of our veterinarians, Dr. Kat Geating, was recently interviewed by ABC7 Bay Area about the dangers of lepto and how this disease impacted one of her patients, Bubba.
“Lepto is a really important disease. It’s one of those things—every single day, every single appointment, I’m educating clients on how serious it is,” says Dr. Geating. “Here in the Bay Area, I tell owners any puddle of water means your dog can be exposed.”
The chance of transmission spikes when it rains, and when these spikes happen, the consequences for unprotected dogs can be devastating.
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How is lepto transmitted?
Leptospirosis is a zoonotic disease, meaning it can infect both animals and humans. It’s important to note, however, that direct transmission from a dog to its owner is uncommon. Most human infections, like most canine infections, result from contact with contaminated water or soil, not from a household pet.
The risk of exposure to leptospirosis increases when your dog:
- Walks through standing water
- Drinks from puddles, ponds, or slow-moving creeks
- Sniffs or licks contaminated soil
- Interacts with wildlife, rodents, and farm animals
- Visits dog parks, boarding facilities, or training centers
The bacteria can enter through small cuts or abrasions in the skin, or through the eyes, nose, or mouth. All dogs are at risk, regardless of age, breed, lifestyle, geographic location, or time of year.
“Every single year when it starts raining here in the Bay Area, I see most of my lepto cases,” says Dr. Geating. “When water sits for a long time, so you think of your dog park where there’s a field and water is just sitting in the grass. That can create a biofilm, and then you can have a really high concentration of leptospirosis infection in that still water.”
Signs and symptoms of lepto
One of the most dangerous aspects of lepto is that the early signs can be non-specific. These symptoms can escalate quickly as the bacteria attack the kidneys and liver.
Common symptoms in dogs include:
- Increased thirst and urination
- Decreased appetite
- Fever
- Lethargy
- Weight loss
- Dehydration
- Difficulty breathing
- Vomiting
- Diarrhea
- Muscle pain or stiffness
“If you’re worried that your pet might have it—the first clinical symptoms and the most common ones that we see are increased thirst, urination, and decrease in appetite,” says Dr. Geating.
How is lepto treated?
Lepto can mimic other diseases, so diagnosis requires a thorough evaluation. If you’re concerned about your dog’s health, please schedule an appointment with your veterinarian. It’s also helpful to keep a log of your dog’s recent activities, travel history, and possible exposure to share with your veterinarian.
When caught early, many dogs recover from lepto. However, even with treatment, permanent kidney or liver damage can occur. Dogs with severe respiratory involvement have a lower chance of survival.
Without treatment, infected dogs can continue shedding the bacteria in their urine for weeks to months. With appropriate antibiotics, shedding often stops within days to a week. Taking action protects your dog, your family, and your community.
Preventing lepto
Lepto can be life-threatening. The good news is that it is also preventable. The most important step you can take is vaccination.
Lepto is not a new threat in our region, and our current vaccine recommendations reflect that. For years, the conventional wisdom was that lepto vaccination was only necessary for dogs with an active outdoor lifestyle. We now know that any dog in an urban environment can be exposed, and that the vaccine is safe and effective protection.
For these reasons, the SF SPCA considers the lepto vaccine a core vaccine for dogs. It requires an annual booster to remain fully effective.
In addition to vaccination:
- Avoid letting your dog drink from or play in stagnant water
- Discourage licking paws after walking through puddles
- Prevent rodents in and around your home
- Seek veterinary care immediately if symptoms appear
If your dog is due for their vaccines or if you’re concerned your dog may have lepto, please schedule an appointment with the SF SPCA Hospital.