Leptospirosis in Dogs

Causes, Treatment, and Prevention

Vet examining dog
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Any dog that makes contact with still water infected by animal urine is at risk of contracting leptospirosis, a harmful bacterial infection. Leptospirosis will cause your dog to display many uncomfortable symptoms and can lead to organ failure if treated late. All dogs can contract leptospirosis, but dogs who have especially outdoor lifestyles are at higher risk because of increased contact with dirty water and wild animals. A vet can diagnose leptospirosis through specialized tests and usually begin treatment with an antibiotic. Dogs who are treated promptly have a high chance of recovery. Leptospirosis can be spread to humans, although not often. You can prevent the disease by controlling your dog's environment and access to potential sources of contamination.

What is Leptospirosis?

Leptospirosis is a bacterial disease caused by the bacteria Leptospira and can be found in water, soil, and damp grass. It is usually spread through infected urine in water that contacts a dog's mouth, nose, or eyes. Leptospirosis can also be contracted by eating the carcass of an animal carrying the disease. The disease can cause kidney failure, liver failure, and lung disease.

Symptoms of Leptospirosis in Dogs

Leptospirosis symptoms are wide-ranging and nonspecific. Your dog will usually begin to exhibit symptoms one to two weeks after exposure but, in some cases, won't exhibit symptoms at all. If you suspect that your dog has leptospirosis, visit your vet right away.


  • Fever
  • Joint and muscle pain
  • Decreased appetite
  • Lethargy
  • Nausea
  • Excessive thirst
  • Frequent urination
  • Gum and eye discoloration

Many of the symptoms of leptospirosis overlap with those of other conditions, so making an at-home is usually difficult. Leptospirosis can damage a dog's kidney, causing symptoms similar to kidney disease, namely excessive thirst and frequent urination. This is also true of signs of liver failure because leptospirosis can cause liver damage. 

signs of leptospirosis in dogs illustration
Illustration: The Spruce / Kelly Miller

Causes of Leptospirosis

  • Exposure to contaminated matter: The most common cause of leptospirosis is contact with bacteria through matter contaminated with infected urine. The bacteria can enter your dog's body through any mucus membranes. If your dog drinks contaminated water from a puddle, gets contaminated mud in its eye, or sniffs contaminated dirt, it is at risk of contracting leptospirosis.
  • Exposure to wild animals: Leptospirosis is transmissible through close contact between animals, most commonly in the ingestion of an infected carcass or a bite from an infected animal.
  • Lifestyle: While all dogs can contract leptospirosis, a dog's lifestyle can heighten its chances of exposure to the disease. Dogs who hunt, swim, or have frequent contact with wild animals are at higher risk of contracting leptospirosis. Still, vets mustn't exclude the diagnosis from dogs who live in urban settings.

Diagnosing Leptospirosis in Dogs

There are a variety of ways to test for leptospirosis in dogs. Most commonly, a vet will run a MAT test (microscopic agglutination test), which measures antibodies to the Leptospira bacteria. Your vet may also run a PCR-DNA test, which detects the presence of Leptospira DNA in the blood and urine. Your vet must give the PCR-DNA test before your dog is administered antibiotics. A combination of PCR-DNA and MAT testing is ideal. Leptospirosis cannot be diagnosed with blood analysis alone, but it can still provide valuable general health information.

Treatment & Prevention

Your dog's treatment plan will significantly depend on the stage and severity of the infection. When caught early, your vet will likely begin treatment for leptospirosis with antibiotics. Supportive care and symptom relief treatments will also likely be prescribed, such as appetite stimulants, anti-nausea medication, and IV hydration. Sometimes, in advanced cases, a dog will require dialysis.

The best way to prevent leptospirosis is to decrease your dog's access to areas with standing water and contact with rodents and wild animals. Vaccines against leptospirosis are available and recommended but do not provide protection from all bacterial strains and need to be administered annually.

Prognosis for Dogs With Leptospirosis

Dogs treated early and aggressively have an optimistic prognosis, especially dogs who do not have organ damage. Antibiotics are usually very effective. Dogs who develop respiratory infections have a poorer diagnosis. Dialysis can be incredibly effective, with an 80% survival rate in dogs who were initially given a terminal renal failure diagnosis. If your dog needs dialysis but does not receive it, it will die. Still, there is a risk of permanent renal and lung damage.

Is It Contagious to Humans?

Leptospirosis is a zoonotic disease that, although uncommon, is contagious to humans. By the same means that dogs become infected, humans can contract leptospirosis through contact with water contaminated with animal urine. Contact usually happens through rat urine, dog urine, and handling farm animals. The risk is higher in humid, tropical climates. If your dog has leptospirosis, exercise caution when providing care. Leptospirosis causes flu-like symptoms in humans and can progress to severe illness. With prompt treatment, symptoms will resolve in two to three days, but recovery may take months if untreated. 

  • Can my dog get leptospirosis in an urban setting?

    Your dog can get leptospirosis, even in an urban setting. No matter where a dog lives, it can come into contact with an infected animal carcass or drink from a puddle containing infected urine.

  • Is there a vaccine for leptospirosis?

    There is a vaccine to help defend against leptospirosis, but it isn't comprehensive and must be administered every 12 months.

  • Will I definitely get leptospirosis from my infected dog?

    While humans can contract leptospirosis from an infected dog, it is unlikely and preventable with proper precautions. If your dog is infected, make sure not to come into contact with its urine. Change your dog's bedding often and wash your hands frequently.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
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  1. Leptospirosis in Dogs. Merck Veterinary Manual.

  2. Sykes, J. E. et al. 2010 ACVIM Small Animal Consensus Statement on Leptospirosis: Diagnosis, Epidemiology, Treatment, and PreventionJournal of Veterinary Internal Medicine25(1), 1–13, 2011. doi:10.1111/j.1939-1676.2010.0654.x

  3. Canine Leptospirosis. Washington State Department of Health.

  4. Leptospirosis. CDC.