At AcuteVet Animal Urgent Care, we believe that educating pet owners about infectious diseases is an important part of protecting both animal and human health. Leptospirosis is one of the most significant infectious diseases we see because it can affect multiple organ systems, cause life-threatening illness and be transmitted from animals to people. Understanding how leptospirosis is spread, what symptoms to watch for, and how it is treated can help owners seek veterinary care as early as possible.

Leptospirosis is a bacterial disease caused by several species of Leptospira bacteria. These bacteria thrive in warm, moist environments and can survive for extended periods in standing water, mud, damp soil, and other wet conditions. The disease is found not only throughout the United States but around the world.

Once the bacteria enter a pet’s body, it spreads through the bloodstream and can invade multiple organs. The kidneys and liver are most commonly affected, although the lungs, eyes, nervous system, and blood vessels can also become involved. The severity of illness can range from mild disease to severe organ failure.

Transmission:

Leptospirosis is most commonly spread through contact with the urine of infected animals. Wildlife such as rats, mice, raccoons, skunks, opossums, and other mammals can carry the bacteria and shed it into the environment via their urine. When urine contaminates water, soil, or other surfaces, the bacteria may remain infectious for weeks to months under favorable conditions.

Dogs most often become infected by drinking urine contaminated water, swimming in ponds, streams, puddles, or floodwater, or by coming into contact with contaminated soil and mud. Infection can occur when the bacteria enter through the mouth, nose, eyes, or small breaks in the skin. Dogs may also become infected through contact with infected wildlife or their urine.

Cats appear to be more resistant to developing severe clinical disease than dogs, but they can still become infected. In some cases, cats may carry the bacteria without showing obvious signs of illness.

Symptoms:

The symptoms of leptospirosis can vary considerably depending on the organs affected and the severity of infection. Some pets initially develop vague signs that resemble many other illnesses, which can make early diagnosis challenging.

Many affected pets experience lethargy, weakness, fever, loss of appetite, vomiting, diarrhea, dehydration, and weight loss. Some animals may seem painful, stiff, or reluctant to move because the infection can cause significant muscle inflammation and discomfort.

As kidney damage develops, owners may notice increased thirst and urination. In more advanced cases, urine production may decrease significantly as kidney function worsens. Severe kidney injury can lead to profound dehydration, bad breath associated with toxin buildup, and oral ulcerations.

When the liver becomes affected, pets may develop jaundice, which appears as a yellow discoloration of the gums, skin, or whites of the eyes. Owners may also notice dark-colored urine or changes in stool color.

In severe cases, leptospirosis can affect the lungs and blood-clotting system. These patients may develop difficulty breathing, coughing, bruising, bleeding abnormalities, collapse, seizures, or sudden death. Because the disease can progress rapidly, prompt veterinary evaluation is critical whenever these symptoms are observed.

Testing:

Veterinarians typically use a combination of physical examination findings, laboratory testing, and specialized infectious disease testing to diagnose leptospirosis.

Bloodwork often reveals evidence of inflammation or infection, including elevated white blood cell counts. Some patients may have low platelet counts, which can contribute to bleeding abnormalities. Changes consistent with anemia may also be present.

Serum chemistry testing frequently shows elevations in kidney values such as blood urea nitrogen (BUN) and creatinine, indicating kidney injury. Liver enzymes and bilirubin levels may also be elevated when liver involvement is present.

Urinalysis may demonstrate dilute urine despite dehydration, protein loss through the kidneys, blood in the urine, or other indicators of kidney dysfunction.

Because routine bloodwork findings are not specific for leptospirosis, additional testing is required for confirmatino. Polymerase chain reaction (PCR) testing may be used to detect bacterial DNA in blood or urine samples, while antibody testing can help identify exposure and infection. In some cases, paired antibody titers obtained several weeks apart are necessary to confirm the diagnosis.

Diagnostic imaging such as radiographs or ultrasound may be recommended to evaluate the kidneys, liver, lungs, and other organs for evidence of damage or complications associated with infection.

Treatment:

Leptospirosis is considered a serious medical condition that requires aggressive treatment. Many pets will require hospitalization, particularly when significant kidney or liver injury is present.

Antibiotic therapy is the cornerstone of treatment. Initial antibiotics are used to control the active infection, followed by additional antibiotic therapy aimed at eliminating the bacteria from the kidneys and reducing the risk of continued shedding in the urine. It is essential that all prescribed medications be administered exactly as directed and completed even if a pet appears to have recovered.

Intravenous fluid therapy is commonly used to correct dehydration, support kidney function, improve circulation, and address electrolyte abnormalities. Depending on the severity of illness, additional supportive care may include anti-nausea medications, appetite stimulants, pain management, nutritional support, oxygen therapy, and, in some cases, blood product transfusions.

Hospitalization may last several days or longer depending on the patient’s response to treatment and the degree of organ involvement. Close monitoring allows the veterinary team to assess kidney and liver function, hydration status, urine production, and overall recovery.

Long Term Outcome:

The prognosis for leptospirosis varies depending on how quickly treatment is initiated and the extent of organ damage present at the time of diagnosis. Many pets recover successfully when diagnosed and treated early. These animals may return to a normal quality of life following completion of therapy.

However, some patients experience permanent damage to the kidneys or liver despite successful elimination of the infection. Chronic kidney disease is one of the more common long-term consequences of severe leptospirosis. Some pets may require ongoing monitoring and management of residual kidney or liver dysfunction throughout their lives. While many pets do very well, severe untreated cases can be fatal.

Human Infection:

One of the most important aspects of leptospirosis is its zoonotic potential. This means that infected animals can transmit the disease to people. Humans most commonly become infected through contact with contaminated urine, water, soil, or surfaces. The bacteria can enter the body through cuts or abrasions in the skin, as well as through the eyes, nose, and mouth.

When caring for a pet diagnosed with leptospirosis, special precautions should be taken. Owners should wear disposable gloves when handling urine-soaked materials or cleaning accidents, wash their hands thoroughly after contact with their pet, and disinfect contaminated surfaces according to their veterinarian’s recommendations. Care should be taken to avoid direct contact between urine and exposed skin.

Although transmission from pets to people is relatively uncommon when appropriate precautions are followed, it remains a significant concern because human illness can be serious.

In people, leptospirosis often begins with symptoms that resemble influenza, including fever, chills, headache, muscle aches, fatigue, nausea, vomiting, and diarrhea. In some individuals, the infection can progress to severe disease involving the kidneys, liver, lungs, or central nervous system. Patients may develop jaundice, kidney failure, meningitis, respiratory distress, or life-threatening bleeding complications. While many people recover fully with medical treatment, like our animal counterparts, severe infections can be fatal.

Anyone who develops illness after exposure to a pet diagnosed with leptospirosis should seek medical attention promptly and inform their healthcare provider about the potential exposure.

Prevention:

Vaccination remains one of the most effective tools available for reducing the risk of leptospirosis in dogs. While no vaccine provides complete protection against every strain of the bacteria, vaccination significantly decreases the likelihood of severe illness and reduces bacterial shedding.

Additional preventative measures include limiting access to standing water, controlling rodent populations around the home, reducing exposure to wildlife when possible, and promptly cleaning areas contaminated with animal urine.

In Summary:

Leptospirosis is a potentially life-threatening bacterial infection that can affect both pets and people. Because the disease can cause severe kidney and liver injury and carries important public health implications, early recognition and treatment are essential. Prompt veterinary care can dramatically improve the chances of recovery and may help reduce the risk of long-term complications.

If your dog or cat has been exposed to standing water, wildlife, or potentially contaminated environments and is showing signs of illness, we encourage you to seek veterinary evaluation as soon as possible. Early diagnosis and treatment can make a significant difference in your pet’s outcome and help protect the health of everyone in the household.