The Leptospirosis Vaccine: From Optimal to Essential
Ever wonder why your veterinarian recommends so many vaccines for your pet? It’s a common question—and no, it’s not about money. The reality is that animals have a talent for putting their noses into everyone’s business, with absolutely no sense of boundaries.
Over the past year, veterinarians have increasingly recommended a vaccine that has actually been around for quite some time: leptospirosis. Historically, this vaccine was considered “elective” or lifestyle-based, meaning it was recommended only for dogs with certain risk factors. However, in June 2024, both the American College of Veterinary Internal Medicine (ACVIM) and the World Small Animal Veterinary Association (WSAVA) reclassified the leptospirosis vaccine as a core vaccine—one that is recommended for most dogs. This change has led to a significant shift in how often the vaccine is advised.
What Is leptospirosis?
Leptospirosis is a bacterial infection that affects both dogs and people. The bacteria thrive in warm, wet environments, including stagnant water and damp soil. It is spread through the urine of infected animals—most commonly rodents, small mammals, raccoons, and some livestock.
One of the reasons leptospirosis is so concerning is that the bacteria can survive in the environment for extended periods before infecting a new host. Transmission becomes more common after heavy rainfall or flooding. Dogs can become infected when the bacteria enter the body through broken skin or through the eyes, nose, or mouth. Even the classic post-walk paw licking can lead to an infection if a pet has been walking through a puddle or grass containing leptospirosis.
Everyday items can pose unexpected risks: food contaminated by rodent urine, outdoor toys left in soil, or puddles encountered on routine walks. As urban wildlife becomes more prevalent, these exposures are increasingly difficult to avoid. This growing risk is a major reason veterinary organizations reassessed the disease and elevated the vaccine to core status.
What happens after transmission?
Once inside the body, the bacteria infect the lining of blood vessels and commonly cause damage to the kidneys and liver, though the disease can spread throughout the body. Affected dogs may develop fever, lethargy, decreased appetite, vomiting, diarrhea, and in more severe cases, jaundice (yellowing of the skin or eyes).
Depending on the severity of the illness, some dogs may be treated at home with antibiotics, however more severe cases require hospitalization, intravenous fluids, and antibiotics. Even with treatment, some patients are left with permanent kidney or liver damage.
Importantly, leptospirosis is a zoonotic disease, meaning it can spread from animals to people. Pet owners are therefore also at risk when a dog becomes infected.
Why is this now a core vaccine?
Due to increasing urbanization, higher rodent populations in cities, changing weather patterns, seriousness of the disease, and the risk to human health, leptospirosis is now considered a threat to most dogs—regardless of lifestyle.
Currently in California, there is a reported leptospirosis outbreak in Berkeley, which began in January 2026 in a homeless encampment where rat exposure was significant. This serves as a reminder that leptospirosis is not limited to rural or outdoor-only dogs.
The biggest change moving forward is clear: the leptospirosis vaccine is now recommended for all dogs, regardless of lifestyle, while always taking each patient’s individual needs into account. We want people and pets alike to stay as safe as possible, and because we can’t control where our dogs sniff or what they may be exposed to, vaccination remains one of the most effective ways to protect dogs as well as their families.
