Leptospirosis in Dogs

Leptospirosis in Dogs

A young dog goes for a run.A young dog goes for a run.
A young dog goes for a run.A young dog goes for a run.

Table of Contents:

  1. Overview of Leptospirosis in Dogs
  2. Pathophysiology
  3. Clinical Signs
  4. Diagnosis
  5. Treatment
  6. Preventive Care
  7. Can Cats Get Leptospirosis?
  8. Human Health Risk

Overview of Leptospirosis in Dogs

Leptospirosis is a common disease that can affect both animals and people. It is specifically classified as a zoonotic because it can be transmitted from animals to people. Leptospirosis is caused by a spirochete in the genus Leptospira. The organism is a spiral-shaped bacterium with hook-shaped ends that make a characteristic writhing and flexing movement.

There are 21 different species and more than 250 serovars (different varieties) of spirochetes. They live in fluids from infected animals, including urine, saliva, blood, and milk. The disease is transmitted by direct contact with the fluids or with an infected animal. It is also transmitted by indirect contact, such as vegetation, food and water, soil, and bedding materials. Spirochetes can survive for weeks to months in soil saturated with infected urine. The bacteria can enter the body through mucous membranes or through breaks in the skin.

Any age, breed, or sex of dog is susceptible to leptospirosis. There is a higher prevalence of cases in the East, Midwest, and Southwest states in the US, specifically areas with forested land and exposure to wildlife. The Appalachian region had the highest prevalence of cases in a 2004 retrospective study.

Other risk factors that were identified in dogs include:

  • Being under 5 years of age
  • Being male
  • Living in an environment with high rainfall and humidity
  • Exposure in the fall season

Wild animals like skunks, raccoons, and opossums are a major source of infection, although pigs, rats, and other animals may harbor the organism and serve as reservoirs of infection. Direct spread is enhanced by crowding of animals, such as in kennel situations. Indirect transmission can occur if susceptible animals are exposed to contaminated food, soil, water, or bedding. Stagnant or slow-moving warm water provides an excellent habitat for the organism. This explains the increase in cases during periods of flooding.

The most common serovars that can cause disease in dogs in the United States include:

  • Icterohaemorrhagiae
  • Canicola
  • Pomona
  • Bratislava
  • Autumnalis
  • Ballum
  • Grippotyphosa


Once the organism penetrates the body, replication occurs in the lymphatic system and is then spread throughout the body through the bloodstream. The incubation period is documented to be from 1 – 7 days after exposure before clinical signs are noted. The organism penetrates through the inflamed vessels and invades other organs like the kidneys, liver, spleen, eyes, and reproductive tract. The body makes an immune response and eliminates the organism from most organs. Unfortunately, organisms tend to persist in the kidneys and can be released into the urine for several weeks or months in carrier animals.

The most common organs that are affected by the bacteria are the kidneys, liver, eyes, platelets, and lungs. Infections can vary from being mild to life-threatening renal failure.

Clinical Signs

Initial clinical signs seen with this infection include:

  • Lethargy
  • Fever
  • Vomiting
  • Diarrhea
  • Increased drinking/urination
  • Decreased to no appetite
  • Possible abdominal pain
  • Jaundice/icterus


Diagnosis of leptospirosis is made by your veterinarian by obtaining a detailed medical history, including previous vaccination status and possible exposure to leptospirosis endemic areas. A physical examination is completed to look for clinical abnormalities and rule out other disease processes that can cause similar clinical signs. Initial blood work is completed to evaluate for abnormalities. A complete blood cell count (CBC) is conducted to evaluate the white blood cell count (WBC), which may be elevated, and red blood cell count and platelet count, which may be on the decline due to infection.

Your vet may also conduct a chemistry panel, which evaluates a patient’s liver and kidney values for elevation. Occasional chest radiographs will be recommended if trouble breathing, coughing, or cardiac issues are noted. Leptospirosis can cause bleeding into the lungs, so coughing or trouble breathing is occasionally seen. A urine sample is collected and sent to the lab to evaluate for kidney function and can be used for more specific leptospirosis testing.

Specific leptospirosis testing options:

  • PCR (Polymerase Chain Reaction). This test is used during the acute phases of the illness. Ideally, PCR will be submitted for blood and urine before antibiotics have been initiated and provide a quick and reliable test for leptospirosis.
  • Antibody titers. These can be useful later in the course of disease after the body has mounted antibodies to the infection. Antibody titers are commonly low during the beginning phase of the disease, but titers done two weeks later and compared to the initial titer can be used for a positive diagnosis.
  • Culture. Culture of leptospirosis is not commonly recommended due to the length of time for growth at the lab, as well as turnaround time.
  • Point of care antibody test. This is a commercially available, in-hospital snap test that looks for IgM antibodies that can be performed by your veterinarian if they have a high suspicion of leptospirosis.


Treatment is started immediately if leptospirosis is a concern while further confirmatory testing is pending. It is based on tending to clinical signs with IV fluids for dehydration, anti-nausea medications, gastroprotectants, and broad-spectrum antibiotics. Antibiotics like penicillin or tetracycline are usually started at this point. Dogs that progress to renal failure may need dialysis to help with recovery. Occasionally, blood transfusions are needed if the patient is having blood loss or needs large volumes of IV fluids. At least two weeks of doxycycline is recommended to eliminate the carrier state of the bacteria.

Recovery was noted to be 80% in dogs that were treated aggressively in the hospital, with some patients needing dialysis for kidney support.

Preventive Care

  • Vaccination. Prevention is available in the form of vaccinations, which provide protection against serovars (subtypes) canicola and icterohaemorrhagiae, with some newer vaccine brands adding protection against pomona and grippotyphosa. Despite this, immunization is recommended. Any dog that has a risk of exposure should be vaccinated.
    • Please note, leptospirosis vaccines need to be boostered yearly.
    • No additional adverse reactions were noted with the leptospirosis vaccines when compared with core dog vaccines.
  • Avoid exposure.
    • Limit exposure to wildlife
    • Do not allow drinking from stagnant water
    • Practice rodent control
    • Isolate any dog that has clinical signs or is positive for infection. This will minimize exposure to other house pets and people

Can Cats Get Leptospirosis?

While cats have been demonstrated to contract leptospirosis, clinical disease is rare. Serovars canicola, grippotyphosa, and pomona have been isolated in cats, but clinical signs were mild. Exposure is thought to be secondary to rodent contact. No vaccines are currently available or recommended for cats with leptospirosis

Human Health Risk

Leptospirosis is a zoonotic disease, which means that people can be exposed from the same environmental source as dogs or by an infected dog. Any person who has been exposed to leptospirosis or has a dog that is being treated for this disease should contact their family physician and discuss monitoring, testing, and treatment if necessary. Personal hygiene should be taken when handling or cleaning up an infected dog’s urine, saliva, or bodily fluids. Any environment that could have been exposed to infected fluids should be thoroughly cleaned. Pet owners that are immunocompromised should take more precautions when in contact with an infected dog.

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