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Leptospirosis: From Dead Seals to City Parks

Posted by The San Francisco Dog Walker

Leptospirosis warning

Leptospirosis is one of the most serious infectious diseases threatening San Francisco dogs. This potentially fatal bacteria lurks in our parks, on our beaches, and anywhere infected wildlife has been. Unlike many dog diseases that remain rare, Leptospirosis experiences periodic surges in the Bay Area—and when outbreaks occur, the consequences can be devastating.

What makes Leptospirosis particularly concerning is its dual source of exposure in San Francisco: dead or dying marine mammals washing up on our popular off-leash beaches, and contaminated puddles and mud in our urban parks left by raccoons, rats, and other wildlife. Your dog can encounter this deadly bacteria on a routine walk through McLaren Park just as easily as during a beach day at Fort Funston.

Critical Warning: Leptospirosis can kill your dog and infect humans. It's preventable through vaccination, but the vaccine is not automatically included in your dog's standard shots. You must specifically request it.

What Is Leptospirosis?

Leptospirosis (commonly called "lepto") is a bacterial infection caused by spiral-shaped bacteria called Leptospira. There are over 200 different serovars (types) of Leptospira, and different serovars are carried by different animal species.

How Transmission Works

Leptospira bacteria live in the kidneys of infected animals and are shed in their urine. The bacteria can survive in:

The bacteria remain viable for weeks or even months if conditions are right—moist, warm, and neutral pH. San Francisco's mild, damp climate provides ideal conditions for Leptospira survival.

How Dogs Get Infected

Dogs contract Leptospirosis when the bacteria enter their body through:

This means your dog doesn't need to drink from a puddle to get infected—simply walking through contaminated mud or sniffing where an infected animal has urinated can be enough if the bacteria come in contact with their nose, mouth, or eyes.

San Francisco's Unique Leptospirosis Risks

San Francisco faces Leptospirosis threats from two major sources:

Marine Mammals: The Beach Threat

Dead or dying seals and sea lions regularly wash up on San Francisco beaches, particularly at:

Marine mammals are known carriers of Leptospira, and their carcasses remain infectious for days or weeks. The bacteria concentrate in the animals' kidneys and urine, but contaminate surrounding sand and water as the body decomposes.

Dogs are naturally curious about dead animals. They investigate, sniff closely, roll on them, or even attempt to eat parts of the carcass—all of which can lead to infection.

Urban Wildlife: The Park Threat

San Francisco's parks harbor healthy populations of wildlife that carry and shed Leptospira:

These animals urinate freely as they move through parks, contaminating:

Why Outbreaks Occur After Rain

Leptospirosis cases in San Francisco typically surge after periods of heavy rain because:

The pattern is predictable: after a wet winter, spring brings increased Leptospirosis cases as dogs who've been exposed during rainy months begin showing symptoms.

Symptoms of Leptospirosis

Leptospirosis symptoms can range from mild to fatal, and unfortunately, early signs are often vague and easily mistaken for less serious illnesses.

Early Symptoms (First 2-7 Days):

These nonspecific symptoms make early diagnosis challenging. Many owners think their dog has a mild stomach bug or is just tired from too much exercise.

Progressive Symptoms (As Organs Fail):

Severe Cases:

In severe infections, dogs can develop:

This Is An Emergency: If your dog has been in areas with potential Leptospirosis exposure and develops fever, lethargy, vomiting, or decreased urination, contact your vet immediately. Early treatment significantly improves survival rates.

Diagnosis and Treatment

How Vets Diagnose Leptospirosis

Diagnosis requires:

The challenge is that definitive test results can take days, so treatment often begins based on clinical suspicion and initial bloodwork.

Treatment

Treatment must be aggressive and begin immediately:

Prognosis

Survival rates depend on:

With early, aggressive treatment, about 75-80% of dogs survive. However, some dogs are left with permanent kidney or liver damage requiring lifelong management.

Without treatment, Leptospirosis is often fatal.

The Leptospirosis Vaccine: Essential But Imperfect

A vaccine for Leptospirosis exists, and it's absolutely essential for San Francisco dogs. However, dog owners need to understand its limitations.

The Four-Serovar Problem

The currently available Leptospirosis vaccine protects against four serovars:

These are the four most common serovars affecting dogs in North America. However, remember there are over 200 serovars of Leptospira in existence. This means:

The vaccine is not 100% effective. It covers the most likely threats but doesn't protect against every possible Leptospira strain your dog might encounter. Marine mammals, in particular, may carry serovars not included in the vaccine.

What The Vaccine Does Provide

Despite not offering complete protection, the vaccine:

Vaccination Schedule

The Vaccine Is NOT Automatic

Here's what many dog owners don't realize: Leptospirosis vaccine is not included in standard puppy vaccines or routine annual shots.

The DHPP vaccine (commonly called "distemper shot") covers:

Notice what's missing? Leptospirosis.

You must specifically request the Leptospirosis vaccine. Many vets will recommend it, but you need to ensure it's actually given and kept current.

Why Some Vets Don't Automatically Give It

Some veterinarians are hesitant to routinely vaccinate for Leptospirosis because:

However, in San Francisco and the Bay Area, the risk of Leptospirosis exposure is high enough that vaccination is strongly recommended for all dogs who go outdoors.

Prevention Beyond Vaccination

While vaccination is your best defense, additional precautions are important:

At The Beach

In The Parks

At Home

The Human Health Connection

Leptospirosis is a zoonotic disease—meaning it can spread from animals to humans. People can contract Leptospirosis through:

In humans, Leptospirosis can cause:

If your dog is diagnosed with Leptospirosis:

Real Cases in San Francisco

Leptospirosis outbreaks occur in San Francisco with concerning regularity. During active outbreak periods, multiple cases may be documented within weeks or months—often clustered around specific parks or after periods of heavy rain.

These aren't isolated incidents. When conditions are right (rain, wildlife activity, unvaccinated dog population), Leptospirosis emerges as a serious threat to San Francisco's dog community.

The Bottom Line

Leptospirosis is a deadly disease that's preventable through vaccination—but the vaccine is not automatic and doesn't provide 100% protection. San Francisco dogs face unique risks from both contaminated urban parks and marine mammal carcasses on beaches.

After 19 years of walking dogs in San Francisco, I've seen the aftermath of Leptospirosis infections—heartbroken owners, expensive hospitalizations, permanent organ damage, and tragic deaths. Every single case could have been prevented or made less severe through vaccination.

Talk to your vet today about the Leptospirosis vaccine if your dog doesn't have it. Keep boosters current. And practice vigilant prevention: avoid puddles, stay away from dead animals, bring fresh water on walks.

Your dog's life may depend on it. And your own health could be at risk too.

This is one disease where an ounce of prevention truly is worth a pound of cure.