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Leptospirosis in Dogs

A tired dog lays on the floor in front of a chair

Dr. Erica Irish author of Leptospirosis in Dogs

When your pup goes to his veterinarian for his semi-annual checkup, the vet will discuss core versus non-core vaccinations with you. Core vaccinations are immunizations that are recommended for almost all dogs whereas non-core vaccinations are recommended based on risk of contracting the illness.

Distemper, parvovirus, and rabies are examples of core vaccines. Leptospirosis is a non-core vaccination for dogs in many areas. However, veterinarians are starting to see more cases of this illness, and it’s important to consider the vaccine for your pup. What is leptospirosis and why is it becoming an increasing problem in veterinary medicine?  

What is leptospirosis in dogs? 

Leptospirosis refers to having an infection with a species ofLeptospira bacteria. These bacteria are calledspirochetes because of their twisted or helical shapes. There are several different species ofLeptospira that can cause leptospirosis in dogs, and the infection typically affects the liver and the kidneys.

Leptospirosis can be caused by almost any mammal, including humans. The most common carriers forLeptospira bacteria are rats and rodents, and in areas where there is a lot of wildlife, there is an increased risk for exposure to these bacteria. Leptospirosis is zoonotic which means that it can spread from animals to humans. This is one of many reasons why vaccination against leptospirosis is important.

Leptospira bacteria can be shed through many bodily fluids but the most common fluid is urine. It can contaminate water and infects dogs who drink the water or swim in it. This feature makes it especially prevalent in the Southern states where annual rainfall is quite high, extending from the end of Spring through the Fall.


Roughly one in four dogs can be exposed toLeptospira bacteria and can be asymptomatic carriers. Dogs with symptoms may become acutely ill and start shivering due to the development of fever. This can make many pups feel very lethargic and may cause them to stop eating.

Appetite can also be impacted by a kidney infection due to leptospirosis. Kidney disease can cause nausea, vomiting, and gastrointestinal upset. It can also cause increased thirst and urination. The liver, too, can be impacted by this disease, and so you may seejaundice or yellowing of your dog’s eyes and skin.


If you are seeing any of these abnormal signs, be sure to contact your veterinarian right away. Your vet may recommend blood and urine testing right away, but the problem with leptospirosis is that it can mimic many other diseases. One rule of thumb is that you should suspect leptospirosis if your dog’s liver valuesand kidney values are elevated on lab work. 

Definitive testing for leptospirosis can also be quite tricky. There is DNA or PCR that can detect the presence ofLeptospira bacteria in blood or urine, but if antibiotic therapy is started before testing can be performed, this may negatively impact test results. Microscopic agglutination testing looks for the presence of antibodies that have been formed againstLeptospira bacteria. However, if antibiotics were started before antibodies could be formed, or if your pup has been previously vaccinated against leptospirosis, testing may yield a false negative result. It can also take many days before there is a test result available. 

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There are two phases of treatment for leptospirosis. The first is to ensure that bacteria are killed in the acute phase of treatment. Penicillin is one of the most common antibiotics to help get treatment started. After that, antibiotics like doxycycline are prescribed to help with the rest of the infection and to help prevent a lifelong carrier status.

If the kidneys and liver are impacted, your pup will need aggressive supportive care to prevent long term damage to his internal organs. This may require days of intravenous fluids and additional treatments based on clinical signs. If your dog is not treated, leptospirosis can cause irreversible kidney and liver damage, both of which can be quickly fatal.

There is a vaccine available for leptospirosis which covers four species ofLeptospira bacteria. It is very effective and can also decrease the severity of clinical signs if an infection does result. This should be repeated annually, especially if you live in an area where there is a higher risk of exposure. However, it is interesting to note that even non-rural places like New York City can have leptospirosis outbreaks. There have been reports where indoor-only dogs who live in apartments have been exposed toLeptospira bacteria thanks to the presence of rats in the building!  

Since leptospirosis is transmissible to other pets and people, it is important to keep infected pups separated from everyone else. Hygiene is essential, especially if you have been exposed to urine, and be careful around sick pups if you have any wounds or cuts in your skin.


Leptospirosis is a highly transmissible bacterial disease that can be spread via wildlife and then passed on to pets and people. Because of the seriousness of the disease’s clinical signs, leptospirosis is a public health hazard that can be mitigated by the routine vaccination of our dogs. If you’re not sure about your pups risk of leptospirosis, ask your veterinarian if the leptospirosis vaccine would be a good idea!  

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Meet The Author 

Dr. Erica Irish author of Leptospirosis in Dogs

Dr. Erica Irish

Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.

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