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The Fickle Phases of Leptospirosis in Dogs

Leptospirosis in dogs is caused by the spirochete bacteria. This bacteria infects dogs and humans. If not diagnosed early, the prognosis is dire.

Warmer weather means swimming, camping, hiking, and biking.  Tropical or subtropical climates present an increased risk of infection and disease from waterborne pathogens.

Studies show a global increase in cases of canine leptospirosis.  Perhaps it’s a sign of climate change. 

We’ve all seen the devastating images of mass flooding on the news. Floodwater of that nature pulls in a wide variety of pathogens that thrive for a long time. It only takes one infected animal to contaminate an entire body of water.

Leptospirosis in dogs is transmitted when the dog:

  • drinks from infected urine
  • is in contact with other domestic animals who have it (through skin cuts, eyes, mouth)
  • drinks or swims in urine-contaminated water (floodwater, rivers, etc.)
  • interacts or lives in close proximity to infected livestock or wildlife

The bacteria lives up to six months in urine-contaminated water. Even the damp soil can harbor the bacteria.

This creates a risk of infection through scratches, scrapes, open wounds, and mucous membranes.  Dogs can transmit the bacteria to humans. However, the number of reported cases is relatively low.

The Worst Sign of Infection is No Infection At All.

Early detection of leptospirosis in canines is treatable. The problem lies in the difficulty of diagnosis.  The most commonly seen patients are considered “clinically inapparent”.  That simply meaning the dog has no obvious symptoms.

In the beginning stages, the dog is lethargic and appears under-the-weather.  The reality is that most of the time, there really isn’t anything seriously wrong with the dog.  However, if you’ve been near floodwater recently or live in a susceptible area, ask the veterinarian to test for leptospirosis.   Better safe than sorry.

Once a diagnosis has been made, the veterinarian will assess whether the dog is in one of the four following categories:

  • per-acute
  • acute
  • sub-acute –  most common
  • chronic


In the acute and sub-acute stages of the disease, clinical signs are evident. Unfortunately, that could mean a grave progression in the disease. Renal failure and liver damage are the top two concerns.  If the dog has developed a cough, it’s likely the bacteria has compromised the lungs.W

Lyme Disease:  The “Second Cousin” of Leptospirosis

You might be surprised to learn that there as many as 230 types of leptospira bacteria and that eight of them are known to cause disease in dogs. The four strains that commonly result in canine infection are:

  • Leptospira icterohaemorrhagiea
  • L. canicola
  • L. grippotyphosa
  • L. pomona

The Borrelia burgdorferi strain of bacteria falls under the larger umbrella and is known to cause Lyme disease .

Leptospirosis Risk Map and Endemic Tick Population Map

The Fickle Phases of Leptospirosis

As frightening as the clinical signs and symptoms seem (see below), the reality is that many dogs present with vague symptoms that could be mistaken for any number of things.  The dog might lack energy, refuse to eat, vomit, or have diarrhea.  In fact, the dog might even appear to recover after a few days.  There’s relief in the eye of the hurricane, until you realize it’s back with a vengeance.

The second phase of leptospirosis erupts with fury, striking its victims with intense symptoms including:

  • Extreme fatigue
  • Anorexia – the dog will not/cannot eat
  • Vomiting – perhaps with blood
  • Painful Abdomen
  • Diarrhea
  • Decreased urination
  • Abnormally rapid breathing
  • fever
  • severe pain in the joints
  • jaundice – often first seen as yellowing in the eyes
  • renal failure
  • liver failure
  • combined renal and liver failure associated with the infection is known as “Weil’s disease”

Eradicating The Disease Through Appropriate Vaccination

The days of many crippling or deadly infectious diseases are seemingly behind us now. The use of vaccines eradicated a host of once-feared diseases such as:

  • smallpox
  • polio
  • whooping cough
  • measles
  • tuberculosis
  • rabies

It’s been over 200 years since the first vaccine was discovered.  Immunization can be credited with saving approximately 9 million lives a year worldwide, and yet there remains skepticism from particular groups on the safety and necessity of inoculation.

There are roughly 100 – 150 outbreaks of leptospirosis in the United States every year.  Over 1 million cases happen globally with an average of 60,000 deaths.

CDC, “Leptospirosis Face Sheet for Clinicians”

American Animal Hospital Association Leptospirosis Vaccination Guidelines

The AAHA does not recommend that dogs be immunized for leptospirosis unless they live in a part of the world considered high-risk.  

Avoiding absolutely unnecessary vaccinations eliminates the side-effect risk factors including:

  1. Facial swelling
  2. Hives
  3. Deadly anaphylactic shock

The controversy surrounding the vaccines offered before 2004 was heightened by the short-term gain stacked against the risks. 

In 2004, a new vaccine released by Wyeth Pharmaceuticals was considered safer and longer lasting. The newer vaccines have essentially removed the unwanted “extras” from the formulation, resulting in fewer side-effects.

It’s suggested that dogs in at-risk areas should only be vaccinated against leptospirosis at 12 weeks of age.  That is considered the absolute minimum age, with an average age of inoculation between 14 and 16 weeks.

Dog Deaths Cause Controversy Over Vaccine

There have always been segments of the population against vaccinations.  The reality is that no vaccination can provide 100% protection, and the risks generally associated with inoculations (from mild to fatal) are considered a lesser worry than the proliferation of the disease itself.

While the debate over the safety of vaccines continues around the world, leptospirosis continues to infect livestock, wildlife, canines, and humans.


The veterinarian will suspect leptospirosis based on a history of the dog’s recent activities, geographic location, and physical symptoms.  It’s important to let the veterinarian know about any and all outdoor excursions as far back as six months.  While the bacteria will die instantly when subjected to hot and dry conditions, it can easily survive up to 180 days in the right climate.

A variety of diagnostic tests including blood and urine analysis will be conducted. If leptospirosis is being considered, the veterinarian will recommend caution when handling the dog as the disease can be transmitted from animal to human. 

A more likely scenario would involve the dog spreading infection to other animals.

Once a diagnosis has been confirmed, the dog will be placed on antibiotics right away. He/she will also be treated symptomatically to alleviate immediate issues like dehydration and pain.


To reduce the risks associated with this particular pathogen, avoid:

  • walking through floodwater
  • avoid rivers (no swimming!) after a heavy rainfall
  • if your drinking water is questionable, boiling or chemically treating it will kill the bacteria.
  • discourage wildlife and rodents from your property
  • treat any cuts and scrapes with protective covering

At The End of The Day…

Use common sense around potentially contaminated water systems. Don’t drink, wash, or bath in rivers or other bodies of water that could be infected with the urine of contaminated wildlife.

Dog parks are the perfect place to give your dog some space to run, but be mindful of interactions with other dogs.  We all love to be “kissed” by our favorite pouch, but considering the contagious nature of leptospirosis, it might be a habit best left aside, especially if you live in a wet climate.  Please view the map above to identify the risks inherent in your neighborhood.

Has your dog been diagnosed with leptospirosis? What did you do?

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