Leptospirosis in Dogs What Pet Parents Need to Know 750

Leptospirosis is a bacterial disease that can affect both dogs and humans. It is caused by spiral-shaped bacteria called Leptospira that thrive in warm, wet environments like stagnant water, flooded soil, sewers, and contaminated food or bedding. Leptospirosis can be fatal if left untreated, so it is crucial for dog owners to understand this disease and be able to recognize early symptoms in their pets.

The good news is that there is a vaccine available to prevent leptospirosis in dogs. As a veterinarian, I recommend all dog owners consider vaccinating their pets, especially those that spend time outdoors hiking, swimming, hunting, or camping where exposure is more likely. Prompt treatment with antibiotics and supportive care greatly improve chances of recovery when started early.

Understanding how leptospirosis spreads, recognizing telltale signs of infection, and seeking veterinary care at the first sign of illness can truly save your dog’s life. Let’s get started.

How Leptospirosis Is Transmitted

Leptospirosis spreads through contact with the urine of infected animals or environments contaminated with the Leptospira bacteria. Most cases of leptospirosis in dogs happen by:

  • Swimming in or drinking contaminated water
  • Exposure to infected urine or tissues
  • Contact with contaminated soil, food, bedding, or garbage
  • Bites from infected animals like rats or raccoons

The bacteria can enter the body through mucous membranes in the mouth/nose or penetrates broken skin. Once inside a dog’s body, the spiral Leptospira bacteria make their way to the blood stream and often localize in the kidneys or liver.

From there, they multiply rapidly and spread back into the environment via shedding in the infected animal’s urine for months at a time. This allows the cycle to continue infecting other animals sharing that environment.

In summary, leptospirosis spreads through:

  • Contaminated water sources
  • Infected animal urine
  • Bites from carrier animals
  • Contact with contaminated environments

Which Dogs Are Most At Risk?

Any dog that spends time outdoors exposed to potentially contaminated water or urine is at risk of contracting leptospirosis. Factors that increase a dog’s susceptibility include:

  • Access to stagnant water or flooding
  • Contact with wild animals
  • Hunting and camping trips
  • Poor sanitation
  • Overcrowding
  • Young or old age
  • Unvaccinated against leptospirosis

While more prevalent in rural settings, leptospirosis can also be found in urban areas—usually connected to rodents, raccoons, and other city-dwelling wildlife.

In summary, dogs most at risk include those that are:

  • Outdoor explorers
  • Unvaccinated
  • Young or senior aged
  • Exposed to wild animals and rural settings
  • Have contact with unsanitary conditions

Pay extra attention to protecting dogs with high exposure lifestyles from leptospirosis.

Common Symptoms of Leptospirosis

The signs of leptospirosis in dogs can vary greatly from case to case. Symptoms often depend on the strain of Leptospira bacteria involved and the individual dog’s immune response.

Many cases start with general, flu-like symptoms which make early diagnosis difficult. Left untreated, the bacteria multiply rapidly and spread to major organs like the liver and kidneys.

Here is an overview of the most common clinical signs of leptospirosis:

Early Stage Symptoms

  • Lethargy
  • Fever
  • Vomiting
  • Diarrhea
  • Loss of appetite
  • Muscle pain
  • Reluctance to move

Later Stage Symptoms

  • Jaundice (yellow gums/skin)
  • Bruising
  • Bloody vomit or urine
  • Abdominal pain
  • Difficulty breathing
  • Organ failure

On average, symptoms tend to appear around 4-12 days after initial exposure to the Leptospira bacteria. However, this incubation period can vary from 2-30 days in some cases.

In mild cases, a dog may show only low-grade fever and act lethargic for a few days before recovering. More severe infections rapidly advance to multiple organ failure and death if left untreated.

If your dog shows any signs of illness after potential exposure to contaminated water or environments, seek veterinary care immediately. Early treatment greatly improves chances of survival.

Health Complications If Left Untreated

Kidney and Liver Disease

The two organs most severely impacted by leptospirosis are the liver and kidneys. If left untreated, over 80% of infected dogs will develop kidney and/or liver problems that continue to worsen.

As Leptospira bacteria multiply, they cause inflammation in the renal tubules of the kidneys as well as liver tissue. This leads to a dangerous decrease in function that prevents these organs from doing their job filtering waste.

Toxins then build up to poisonous levels in the dog’s blood stream, throwing off normal metabolic function. Swelling puts pressure on surrounding organs and can progress to complete organ failure.

Kidney inflammation is especially common and serious due to the localization of Leptospira bacteria. If kidney function deteriorates too far, intensive dialysis treatment and fluid therapy are required to prevent death.

Bleeding Disorders

Certain strains of Leptospira can also disrupt normal blood clotting in infected dogs. This leads to uncontrollable internal and external bleeding seen as:

  • Bruising
  • Bloody vomit/urine
  • Bleeding from the nose/mouth
  • Bleeding within the intestines

Ruptured blood vessels leak iron-rich hemoglobin that causes the yellow/orange staining of the skin and eyes known as jaundice or icterus.

Without treatment, uncontrolled hemorrhaging and anemia can develop rapidly from blood loss and lead to hypovolemic shock.

Heart Disease

More recently, veterinarians have identified Leptospira as a cause of chronic inflammation of the inner lining of a dog’s heart called endocarditis. This can progress to congestive heart failure if left untreated.

Respiratory Distress

As critical organ function declines, a phenomenon called ARDS can occur in dogs with leptospirosis. ARDS stands for acute respiratory distress syndrome.

Fluid leaks out of damaged blood vessels into the air sacs of the lungs. This impairs oxygen exchange and makes breathing increasingly difficult.

Reproductive Issues

Bacterial infection of the uterus, called pyometra, has also been linked to Leptospira in unspayed female dogs. This causes fever, lethargy, vomiting, and discharge.

If not treated promptly, a uterine infection can progress to septic shock and require intensive care or emergency surgery.

In summary, health complications from leptospirosis include:

  • Kidney failure
  • Liver failure
  • Hemorrhagic bleeding
  • Heart disease
  • Respiratory distress
  • Reproductive issues

Diagnosis and Treatment

Early diagnosis and treatment are crucial to saving a dog’s life in cases of leptospirosis. However, definitively diagnosing this complex disease can be tricky.

Let’s explore the diagnostic process and latest treatment options veterinarians use to combat this bacterial infection.

Diagnostic Testing

No single test can conclusively diagnose leptospirosis. Instead, veterinarians rely on a combination of clinical signs and multiple laboratory tests. These include:

  • PCR: This DNA-based test detects genetic evidence of Leptospira bacteria in blood and urine samples. Results come back in about 2 days.
  • MAT: The microscopic agglutination test looks for Leptospira antibodies in blood serum. It can help determine the exact bacterial serovar causing infection. However, it takes 2-4 weeks to show positive results.
  • Blood work: Vets look for elevated liver and kidney enzymes, inflammatory markers, and electrolyte imbalances signaling organ distress.
  • Urinalysis: The presence of blood, protein, bacteria, or casts in urine often indicates kidney inflammation.
  • Imaging: Radiographs and ultrasound allow vets to visually inspect for organ swelling and function.

PCR and MAT testing are most accurate when paired with clinical signs. However, false negatives are common in the early stages before antibodies develop. This makes diagnosis complex.

Treating Leptospirosis

The cornerstones of treatment are antibiotics, fluid therapy, and supportive medications to help maintain organ function.


Early administration of antibiotics is vital to clearing infection and minimizing organ damage. Doxycycline is most often prescribed, but penicillin and amoxicillin are also used.

The antibiotics are continued for 2-4 weeks depending on clinical signs and diagnostic results. Unfortunately, relapses are common after treatment stops.


Intravenous fluid therapy helps flush toxins from the body and provides support when the kidneys and liver are struggling. Fluids also help combat low blood pressure and prevent shock.

Supportive Care

Medications that protect the GI tract, control nausea, boost electrolytes, and support nervous system function are tailored to the patient’s needs. Transfusions of blood or plasma may be given for bleeding disorders.

Ongoing Care After the initial crisis is resolved, follow up care includes:

  • Monitoring blood work for normalizing kidney and liver enzymes
  • Repeat urinalysis to confirm no more blood or bacteria
  • Checking MAT titers to ensure decreasing antibody levels
  • Identifying and eliminating source of infection
  • Discussing vaccine options to prevent future infection


The key to protecting dogs from leptospirosis is prevention. Proactive steps all pet parents can take include:

  • Annual Vaccines: Speak with your veterinarian about the leptospirosis vaccine for your dog. It provides protection against four common strains. Vaccination is highly recommended for outdoor, sporting, and working dogs with high exposure risk.
  • Avoid Standing Water: Pick up bowls, puddles, toys, and other potential sources of standing water in your yard to prevent contamination.
  • Rodent Control: Use humane traps and seal up access points to your home and outdoor buildings to keep wild animals out. Their urine can be a source of leptospirosis.
  • Good Hygiene: Wash your hands after handling animals or cleaning up urine. Use dilute bleach solutions to disinfect contaminated environments.
  • Limit Contact: Keep dogs away from questionable water sources, wildlife, and unknown dogs when out on walks or adventures. Monitor for illness after potential exposure.

While leptospirosis can’t always be avoided, smart preventative care is the best medicine!


Do humans get leptospirosis too?

Yes. Leptospirosis is considered a zoonotic disease, meaning it can spread between animals and people. Humans most often become infected through contact with urine from infected animals or contaminated water/soil. Wear protective clothing and wash hands when dealing with possible sources.

What is the survival rate for dogs with leptospirosis?

With early intervention, dogs have a good chance of making a full recovery. However, the prognosis declines the longer it takes to start treatment. Survival rates vary from 50-90% depending on when antibiotics and supportive care begin.

Can a dog transmit leptospirosis to other pets?

Yes. An infected dog sheds large numbers of Leptospira bacteria in its urine for months after initial infection. This urine can serve as a source of infection for other pets sharing the same environment or water sources. Isolate sick pets and use dilute bleach to disinfect.

Do I really need to vaccinate my indoor dog for leptospirosis?

It depends on your individual circumstances. The lepto vaccine is recommended for dogs with any outdoor access, even if minimal. However, purely indoor dogs may only need to receive this vaccine every 3 years after the initial puppy series rather than annually. Check with your vet.

Can my dog recover kidney function after leptospirosis?

Many dogs regain normal kidney function with prompt care. However, a subset suffer permanent damage that impairs kidney function long term. Lifelong management with special diets, medications, and blood work monitoring helps these dogs live happily.

How do I know if my dog was exposed to leptospirosis?

Unfortunately, it can be difficult to pinpoint a specific source of exposure since Leptospira bacteria are so widespread in the environment. Pay attention for symptoms of illness if your dog spends time in rural settings, goes hunting/camping/swimming, or could have had contact with wild animals or standing water sources. When in doubt, call your vet.

Canine leptospirosis is a complex bacterial disease transmitted through contaminated water or urine that can prove fatal if left untreated. All dog owners should be aware of this disease and its lifesaving vaccine.

By recognizing early flu-like symptoms, seeking prompt veterinary testing and treatment, and taking steps to avoid exposure, we can protect the health of our furry friends.


  • Bouvet, J., Lemaitre, L., Cariou, C., Scotto, M., Blain, C., Oberli, F., Cupillard, L., & Guigal, P. (2020). A canine vaccine against Leptospira serovars Icterohaemorrhagiae, Canicola, and Grippotyphosa provides cross protection against Leptospira serovar Copenhageni. Veterinary Immunology and Immunopathology, 219, 109985. https://doi.org/10.1016/j.vetimm.2019.109985
  • Miotto, B.A., Tozzi, B.F., Penteado, M. et al. Diagnosis of acute canine leptospirosis using multiple laboratory tests and characterization of the isolated strains. BMC Vet Res 14, 222 (2018). https://doi.org/10.1186/s12917-018-1547-4