About Leptospirosis

Leptospira bacteria are the cause of Leptospirosis (Lepto). These bacteria reside in soil and water all around the world. There are many strains of Leptospira bacteria that can cause disease. A result of infection may be fatal liver or kidney failure. This can be a result of Leptospirosis infection for both people and dogs. Additionally, transmission of the bacteria between dogs and humans is possible. Some common Leptospirosis symptoms include sudden fever and illness, sore muscles, shivering and weakness.

Where is Leptospirosis Found?

Leptospirosis is more common in areas with warm climates and high annual rainfall, but it can occur anywhere. Another “hotspot” is areas with lakes, rivers, and wildlife. Exposure to slow-moving or stagnant water is a major risk factor for leptospirosis, although it can also be contracted from wet, shaded grass or along the banks of rivers or lakes. In the United States, the southwestern states appear to have lower risk of leptospirosis because of the dryness. The highest number of leptospirosis cases commonly occurs in the late summer and fall in the United States, but seasonality can vary in different parts of the country.

A study in The Veterinary Journal, stated that a 2017 study showed that leptospirosis in dogs is common, widespread, and in every state in the continental United States. Consequently, the risk of infection rises for dogs that live closer to forests, wild areas, and spread out residential areas. Sadly, in 2022, this is no longer the case. In the last five years, positive lepto diagnosis have been found in urban areas. Please do not consider your pet “safe” because you live in an urban area and/or rarely go to the “country.” With humans encroaching more and more on the natural homes of wildlife, they have nowhere to go but backyards. Additionally, the lakes and rivers we so like to take our dogs to are areas where these wildlife go to get the water they need to survive.

How is Lepto Spread?

Dogs can become infected and develop leptospirosis in multiple different ways.  Mucous membranes or wounds are how this bacteria enters the host’s body. As a result, pregnant dogs with Leptospirosis will pass the bacteria through the placenta. Bacteria can be passed through:

What Animals Are at Risk?

There are multiple animals that can asymptomatically carry Leptospirosis. This bacteria is not deadly to all species. However, Lepto can be deadly to dogs. Leptospirosis in cats is possible, but rare.  In cats, the symptoms and effects appear to be mild. Any area that has standing water and wildlife (this includes squirrels), bares the risk of exposure to Lepto. It does not matter if you live in the country, suburbs, or city. Leptospirosis can affect any dog independent of age, breed, or gender. Common risk factors for leptospirosis in dogs residing in the United States include:

Signs/Symptoms of Leptospirosis

The signs of leptospirosis in dogs vary based on the strain of the bacteria, geographic location, and how the dog’s immune system reacts to the infection. As a result, dogs infected with Lepto can have symptoms that range from non-existent to severe, life-threatening illness. Signs of leptospirosis are rather non-specific. Possible signs/symptoms are:

Possible Risks of Lepto

Sadly, the reaction of the body to this bacteria is so expansive that there is no way to know how each individual case will react. The risk that this bacterium can pose to your dog’s health may be extremely minor and no major symptoms will present. Then, there are dogs that show symptoms, but seem to spontaneously “heal” with no major long-term effects.  On the other hand, for some virulent strains of this bacteria and/or dogs with weakened immune systems (for any reason), this disease can possibly cause bleeding disorders which can lead to:

Leptospirosis Prevention

Since this bacterium can do so much damage, it is smart to be safe rather than sorry.  The prevention of infection is quite easy.  Vaccines are available to effectively prevent leptospirosis and protect dogs for at least 12 months.

Just as Safe as Other Vaccines

Contrary to some reports on the web, the Lepto vaccine is no more likely to cause adverse reactions than are the other commonly administered vaccines. Much of the information associated with this vaccine are based off of when the vaccine was newly available. At that time, there was a higher reaction rate. Nonetheless, over the years, this has reduced greatly due to changes in the vaccine. Annual vaccination for Lepto is recommended for all dogs that live in (or visit) areas where there may be standing water. Talk to your veterinarian about the benefits and risks of vaccination against leptospirosis to determine if vaccination is right for your dog. Reducing your dog’s exposure to possible sources of the Leptospira bacteria can also reduce its chances of infection.

This may include:

Diagnosis and Treatment

The dog’s exposure history and symptoms may cause your veterinarian to consider Lepto. However, symptoms associated with lepto are common in many different diseases. In addition to a physical examination, your veterinarian may recommend blood tests, urine tests, radiographs (x-rays), an ultrasound examination, and/or antibody testing with or without PCR (bacterial DNA testing). The tests recommended are usually based on the severity of disease and the signs observed.

Antibiotics and supportive care is the general treatment for Leptospirosis. Depending on the severity of their illness, affected dogs may require I.V. fluid therapy and nutritional support. In extreme cases there may be a need for oxygen therapy, mechanical ventilation (support for breathing), kidney dialysis, or other intensive care measures might be necessary.


When treated early and aggressively, the chances for recovery are good. Nonetheless, there is still a risk of permanent residual kidney or liver damage. When warranted, early referral for dialysis may provide support until the kidneys recover function and can be lifesaving for dogs if finances allow. Dogs with severe respiratory disease are less likely to recover despite treatment. Other dogs in the household, even if they do not appear ill, will also need to be treated.

Are People at Risk of Lepto Infection?

Yes. As a zoonotic disease, Leptospirosis has the ability to transmitted from animals to people. Just like as in dogs, in humans, infection can cause flu-like symptoms and can cause liver or kidney disease. In the United States, most cases of human leptospirosis result from recreational activities involving water. Infection resulting from contact with an infected pet is much less common, but it is possible.

If Your Dog had Lepto

Although an infected pet dog presents a low risk of infection for you and your family, there is still some risk. If your dog has leptospirosis, the following precautions should be used:

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