Diagnosis and Treatment of Leptospirosis in Dogs

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Vet examining dog
Vet Examining Dog

Leptospirosis can affect many animals, from wild to domesticated. It is rare in cats, but more common in dogs. Leptospirosis is a zoonotic disease, meaning it can be passed from animals to humans. Leptospirosis in humans can cause flu-like symptoms and and even progress to severe illness with kidney or liver failure or meningitis.

What is Leptospirosis?

Leptospirosis is a bacterial disease caused by a complex group of closely related bacteria of the genus Leptospira. There are several strains that occur in different locations and tend to affect certain species more than others. Leptospira bacteria survive especially well in warm, humid areas, and are often found in stagnant water like ponds. Wild animals including city wildlife can carry Leptospira. Therefore, dogs with a higher potential for exposure to contaminated water and exposure to wild animals and their urine are at a greater risk. This includes dogs living in rural areas or dogs that spend a lot of time outdoors like hunting dogs. Outbreaks in cities like Boston and NYC have also occurred.

Signs and Symptoms of Leptospirosis in Dogs

The severity of symptoms varies and depends on the dog (age, immune response, vaccination status), the strain of Leptospira, and other factors. Severe cases can be fatal. Signs and symptoms may include:

  • Fever
  • Joint or muscle pain (this may manifest as a reluctance to move)
  • Decreased appetite and Lethargy
  • Nausea
  • Excessive drinking
  • Frequent urination sometimes followed by lack of urination
  • Yellowing of the gums, membranes around the eyes, and skin (jaundice)
signs of leptospirosis in dogs illustration
Signs Of Leptospirosis In Dogs Illustration

Causes of Leptospirosis

Most cases involve large breed dogs but any dog can be exposed. Both rural and urban dog's can be at risk due to urban wildlife such as rodents that can carry the bacteria. Most infections happen in the summer and early fall, and outbreaks sometimes follow rainfall or flooding. Leptospira bacteria are shed in the urine of infected animals, though they can be found in other body fluids and tissues. Dogs can become infected by exposure to contaminated water (both through ingestion or contact with mucous membranes or broken skin), exposure to urine from an infected animal (e.g. contaminated food, bedding, soil, etc.), bite wounds, and ingestion of tissues from infected animals.

white long-coated dog sitting near post beside building
white long-coated dog sitting near post beside building

Once Leptospira bacteria get into the body, they spread to many types of tissues. The immune system may clear the bacteria from most of the body, but the bacteria may hide out in the kidneys, and the bacteria can be shed in the urine for many months after infection. Treatment with antibiotics may help prevent long-term shedding in the urine.

Diagnosis of Leptospirosis

The most common way to diagnose Leptospirosis is by finding increasing levels of antibodies to Leptospira over time by use of a test called MAT (microscopic agglutination test). A single antibody test may be positive due to past exposure to Leptospira bacteria (e.g. an infection with no symptoms) or vaccination. So often the test is repeated 2 to 4 weeks after suspected leptospirosis infection. Your vet may also suggest a PCR or Lepto SNAP test.

It is also important to note that Leptospirosis can look like alot of other diseases, so often a variety of diagnostics will be needed to help rule out other possible causes of your pet's clinical signs. This may include radiographs, various blood and urine tests and ultrasound.


Antibiotics are used to kill Leptospira bacteria and are often given in two stages: one type of antibiotic to treat the initial infection followed up with a different kind of antibiotic to combat the shedding of bacteria in the urine. The earlier treatment is started, the better.

Most cases of leptospirosis require aggressive intravenous fluid treatment, antibiotics and medications to reduce vomiting and treat other effects of kidney and liver failure. Depending on the severity of disease, treatment is not always successful when organ failure is present. Once kidney or liver failure is present, the prognosis for recovery is worse.

white short coat dog with red scarf
white short coat dog with red scarf
adult black and white border collie on focus photography
adult black and white border collie on focus photography
yellow Labrador retriever hiding on green leaf plants
yellow Labrador retriever hiding on green leaf plants

How to Prevent Leptospirosis

Vaccines against Leptospirosis are available and recommended in areas where Leptospirosis is common. The vaccines are only produced for a few specific varieties of Leptospira and don't offer long-lasting immunity, so need to be repeated annually.

Although the vaccines are not 100 percent effective and do not protect against all types of Leptospira, vaccination is still recommended to help prevent a potentially serious disease that can be transmitted to people. Recommended vaccines and vaccination schedules should be discussed with your vet based on your dog's risk factors. Rodent control measures reduce the chances of infection, and in areas where Leptospirosis is common, preventing dogs from swimming in ponds and slow-moving water can also help.

Human Transmission

Leptospirosis can cause flu-like symptoms in people, which in some cases can progress to serious illness. If any people in contact with a dog diagnosed with Leptospirosis become ill, be sure to mention the dog's illness to health care providers (as a rule of thumb, it is always a good idea to mention pet exposure to health care providers when people in the family are ill or have a compromised immune system).

However, if your pet has been diagnosed with Leptospirosis, steps to prevent infections include the following:

  • Avoid contact with urine if possible, and wear protective clothing (gloves, etc.) if you need to handle urine.
  • Practice good hygiene including careful hand washing.
  • Disinfect surfaces where infected pets have urinated (antibacterial disinfectant or diluted bleach solution).
  • Follow your vet's advice for treatment and make sure all medications are given as directed.