Your dog may love swimming in lakes and romping in the woods, but a dangerous disease lurks in these areas – one that can sicken you as well as your dog. Leptospirosis is caused by a bacteria spread through soil, water, and the urine of infected animals. If not caught and treated early it can be deadly. Fortunately, vaccination can protect dogs from leptospirosis. Preventing your dog from drinking from puddles of standing water or from swimming in lakes, streams, or other bodies of water that may be contaminated also reduces his risk of exposure.


Leptospirosis is a potentially serious disease caused by the bacterium Leptospira interrogans. It affects dogs but can also infect a wide variety of domestic and wild animals, as well as humans.

The organism is usually spread through infected urine, but exposure to contaminated water or soil, reproductive secretions, and even consumption of infected tissues can also transmit the infection. Introduction of the organism through skin wounds can also occur. Carriers of the organism include raccoons, opossums, rodents, skunks, and dogs.

The bacteria can survive for long periods of time in water and are frequently found in swamps, streams, lakes, and standing water. The bacteria also survive well in mud and moist soil, and localized outbreaks can occur after flooding.

Once a dog is infected, the leptospirosis organisms rapidly advance through the bloodstream leading to fever, joint pain, and general malaise. Because the organism settles in the kidneys and actually reproduces there, inflammation and even kidney failure may develop. Liver failure is another common consequence of infection.

Symptoms and Identification

Clinical signs typically develop 2 to 12 days after exposure to the bacterium. In many dogs, infection may remain subclinical (without clinical signs) or chronic. In acute, or more serious cases, dogs may experience potentially fatal kidney or liver disease.

Signs include:

  • Weight loss
  • Fever
  • Inappetence (appetite loss)
  • Vomiting
  • Lethargy
  • Muscle and/or joint pain
  • Diarrhea
  • Bloody urine
  • Excessive thirst
  • Jaundice
  • Excessive bleeding
Leptospirosis can be diagnosed through blood tests; however, tests may need to be performed multiple times to confirm a diagnosis.

Affected Breeds

Dogs of any breed are susceptible to infection with leptospirosis. Dogs used for hunting or other outdoor sporting activities may be at increased risk due to exposure to potentially contaminated areas.


Treatment typically consists of a regimen of antibiotics. Complications such as liver or kidney damage or spontaneous bleeding are treated with fluid therapy and other treatments that are appropriate for the individual patient. Hospitalization is required in many cases.


Exposure to leptospirosis can be reduced by preventing your dog from drinking from puddles of standing water or from swimming in lakes, streams, or other bodies of water that may be contaminated. Unfortunately, for dogs that are accustomed to an active outdoor lifestyle that includes swimming, these precautions may not be practical.

Prevention of leptospirosis is complicated by the fact that there are more than 200 different serovars (subtypes) of the Leptospira interrogans bacterium that can cause illness in animals and people. The available vaccines only protect against a handful of the most common subtypes that infect dogs, which can limit the protective value of the vaccines. Nevertheless, the available vaccines are effective and safe when used as directed, and many veterinarians recommend the vaccination for dogs at risk for exposure. Annual revaccination is required.

The leptospirosis vaccine is not required for all dogs. Your veterinarian may recommend this vaccine based on your dog’s lifestyle and exposure risk.

Because humans can also become infected with leptospirosis, dogs suspected of having the disease should be handled with care. Adhere to good hygiene techniques, such as frequent handwashing and avoiding contact with potentially contaminated urine.

This article has been reviewed by a Veterinarian.