Leptospirosis in Dogs: A Bacterial Disease That’s Spreading

A zoonotic disease that can spread between humans and dogs.
By Shea Cox DVM, CVPP, CHPV, January 2013, Updated June 2021
leptospirosis dogs

Leptospirosis is a bacterial disease that can affect both humans and dogs, and can readily be spread from one species to another (i.e., from our dogs to us). For many years the occurrence of leptospirosis in pets was rare, however, in the past few years, the disease has become diagnosed more frequently–I myself have treated four dogs suspected of having leptospirosis just this past year.

If your dog becomes ill from leptospirosis, the extent of care needed depends on the severity of disease, but the treatment generally requires a hospital stay with extensive supportive therapy.

What Causes Leptospirosis?

Leptospirosis in dogs is caused by the leptospira bacteria which is spread through the urine of infected animals into the soil and water. As dogs come in contact with a contaminated area, the bacteria can be absorbed through skin and mucus membranes (gums, nose, eyes) or through drinking the contaminated water–another reason to stay clear of puddles!

Leptospira bacteria can survive for up to 180 days, given the right conditions. There are several environmental factors conductive to letting leptospira bacteria flourish and increase risk of exposure including warm, damp environments, and stagnant water. With that being said, leptospira do need moist soils to survive, and they will rapidly die on dry surfaces.


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The density of animal population, such as kennels and urban settings, also increases urine contamination and thus exposure. Areas that are heavy populated with rodents or wildlife such as raccoons and skunks also increases risk. These animals serve as “innocent hosts” meaning they are not affected by disease, but they continue to spread it to the environment through urination.

Symptoms of Leptospirosis

The clinical signs of this disease can be vague and mimic many other disease processes.

Signs of leptospirosis in dogs can include fever, lethargy, loss of appetite, muscle stiffness, vomiting and diarrhea. Jandice, a yellowish discoloration of the gums or whites of the eyes can also be observed. In severe cases, this disease moves rapidly and can turn fatal rather quickly. In mild cases, dogs may show no symptoms and the disease may go undetected.

How is Leptospirosis Diagnosed?

Unfortunately, leptospirosis in dogs can look like any other disease, so confirming the infection is generally not easily done when your pet walks into the exam room. This is something that tends to be diagnosed by a second round of tests when the initial blood work and urinalysis look suspicious for disease.

What can raise a suspicion of a leptospira infection is an elevation in both kidney and liver values and sometimes the white blood cell count. If this is observed, your veterinarian will then recommend a special blood and urine test be sent to an outside laboratory. These results can take several days, and so antibiotic treatment is often started prophylactically pending the confirming results.

Most infections are subclinical, which means no signs of disease will ever develop and your pet will never experience illness. However, if your pet does develop sudden signs of disease, and those signs appear severe, we generally give a guarded prognosis (50/50 chance of survival).

Without treatment, leptospirosis can lead to kidney failure, liver failure, and even death. Blood or plasma transfusions are sometimes needed if the body losses its ability to clot due to liver compromise. Yes: this can be one bad bug.

How Can You Keep You and Your Dogs Safe?

It is important to minimize your dogs access to areas with rodents, farm animals, and wildlife to prevent infection. When backpacking with your dog, watch out for areas heavily trafficked by wildlife. Keep your yard clear of stagnant water and clean your home often especially in areas where there is pet urine. In addition to good sanitation practices and limiting your pets access to areas with standing water, there is a vaccine available.

Cases of leptospirosis tend to spike in the late summer and fall or, in cooler climates, during rainy winters. Outbreaks tend to follow seasons with abnormally high rainfall or increased flooding. –Ashley DiPrete RVT, VTS (SAIM)

Vaccines contain what are known as “serovars,” which are “components” of the bacteria used to stimulate protection from disease. However, there is a catch. There are at least nine serovars, or strains, that can cause disease, yet the vaccine contains only a fraction of these, offering incomplete protection. Often people think their dog is safe from disease because it has been vaccinated, but sadly, this is not the case. Additionally, immunity may only last 6-8 months, and some veterinarians recommended that you should vaccinate high-risk dogs (such as dogs who hunt, show dogs, dogs with access to lakes and ponds, and endemic areas) every 4-6 months.

Vaccines do not come without risk, and the use of this vaccine with regards to risk vs. benefit is definitely a conversation to have with your veterinarian. Your veterinarian can assess your dog’s risk of exposure, discuss the most common “local” serovars found in your specific area and can recommend a vaccine protocol that makes sense for your dog.

Photo by 14230021 / Pixabay

Dr. Shea Cox is the founder of BluePearl Pet Hospice and is a global leader in animal hospice and palliative care. With a focus on technology, innovation and education, her efforts are changing the end-of-life landscape in veterinary medicine.

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