Reviewed by Dr. Nicoletta Nica
Updated on 24/06/2026
Reading time 4 min.
Overview
Severity: Low
Life stage: All
Leptospirosis is a severe infection caused by bacteria of the Leptospira genus. These bacteria infect many different types of animals, including dogs, as well as occasionally cats and people. The bacteria cause illness when they enter your body via contaminated water, soil, or urine from an infected animal. Depending on which organs are affected in the infected animal, it may cause damage to one or more organs, such as kidney damage and/or liver damage. Severe cases can be life threatening without treatment.
Dogs are the pet species most commonly affected by leptospirosis. However, many other factors contribute to the risk of developing the disease. Factors include contact with wildlife, rodents, or areas that have standing water. Due to its ability to be transmitted to people (a zoonotic disease), this has significant implications for public health.
Causes
Leptospirosis is caused by contact with Leptospira bacteria that thrive in warm, damp environments.
Common Sources of Infection
- Contact with the urine of an animal infected with leptospirosis (animals like rodents, wildlife, and stray dogs)
- Drinking or swimming in contaminated water (such as puddles, ponds, or a slow-flowing stream)
- Exposure to contaminated soil or a damp environment
- Ingestion of food or water contaminated with infected urine
- Rodents are often the main carriers of bacteria. The rodents can have no symptoms themselves while still excreting bacteria through their urine.
Risk Factors
Certain factors raise the risk of developing leptospirosis.
- Active outdoor lifestyle or regular outdoor work experience
- Living close to farms, forests, and flooded locations
- Access to stagnant water sources
- Poor rodent management
- Warm and humid climate
Symptoms
Symptoms of Leptospirosis may range from mild to very severe, and they will depend upon how severely infected an animal is, as well as what organs of the body have been damaged.
Some dogs can be mildly symptomatic for the disease, whereas other dogs can be very sick.
Early Signs
Early on in the progression of this disease, a dog may exhibit some of these early warning signs:
- Fever
- Lethargy and weakness
- Loss of appetite
- Muscle pain or stiffness
- Vomiting or diarrhea
Severe or Advanced Signs
As the disease continues to progress, it may produce more serious symptoms:
- Jaundice (yellowing of gums, eyes, or skin)
- Blood in urine
- Abdominal pain
- Dehydration
- Bleeding disorders or bruising
- Difficulty breathing in severe cases
If left untreated, Leptospirosis can cause kidney and liver failure or death.
Risks
The risks associated with leptospirosis are severe enough that if left untreated or undiagnosed, it can be fatal.
The Major Health Complications Caused by Leptospirosis
- Acute kidney failure
- Liver failure (liver damage)
- Internal hemorrhage caused by blood clotting disorder complications
- Respiratory symptoms as a result of lung involvement (distress in breathing)
- Failure of multiple organs.
Zoonotic Risk
Direct contact with animal urine containing the bacteria or contaminated water/soil will allow transmission of leptospirosis from animals to humans. Therefore, this disease represents a significant zoonotic risk for both pets and their owners, as well as other personnel at veterinary clinics.
Diagnosis
Diagnosing Leptospirosis can be difficult, as many times symptoms are similar to other conditions that affect the kidneys and/or liver.
Veterinarians may have to combine several diagnostic methods for:
- Blood tests to determine the level of liver and kidney function
- Urine tests for evidence of infection or kidney involvement
- PCR (Polymerase Chain Reaction) Testing to confirm the presence of Leptospira DNA
- Antibody Testing to measure the body’s immune system response
- Imaging studies, when needed to assess organ damage from more severe infections
A quick diagnosis is also critical because it has been proven that treatment works best during the initial stages of an infection.
Treatment
The focus in treating Leptospirosis is to treat the disease itself, keep organs functioning properly, and manage secondary problems caused by the disease.
Treatment with Antibiotics
The best way to treat Leptospirosis is through antibiotics. Antibiotics eliminate the bacteria and help prevent further spread of infection. Depending upon how bad your symptoms were when diagnosed, your veterinarian may need to administer antibiotic treatments for several weeks or even months.
Supportive Care
Leptospirosis can cause many complications in dogs that result in needing intensive care at a veterinary clinic. This type of care may consist of:
- Intravenous fluids administered to support your dog’s kidney function.
- Medication to combat nausea and vomiting.
- Pain control as needed (pain can be an extreme symptom).
- Correction of electrolyte imbalances caused by dehydration.
- Food supplementation to ensure proper nutrition.
- Oxygen as needed.
Prevention
Leptospirosis is very easy to contract when it exists in an environment, and as such, presents a risk to both animals and people alike.
Vaccination
The vaccine is the best method for prevention. The vaccine will decrease the chances of contracting the illness. If a vaccinated dog is exposed to the bacteria while vaccinated, its symptoms will be less severe. Most vaccinations require annual booster shots.
Environmental Control
- Dogs should never drink out of standing water (i.e., puddles)
- Rodents in homes/gardens should always be controlled
- Pets should never go into areas where wildlife has urinated
- The outdoor area should always be kept clean.
Lifestyle Management
- Always watch over pets when they are outside in high risk areas
- Fresh, clean water should always be available to your dog
- Avoid walking dogs in flood prone or heavily contaminated areas.
Also, proper cleaning habits are just as important, especially after being around a pet that may have come in contact with bacteria.
Reviewed by
Dr. Nicoletta Nica
DVM, MRCVS
Dr. Nicoletta was born in Romania and studied veterinary medicine. After graduation Dr. Nicoletta worked for a small animal clinic.


