Leptospirosis in Dogs

Leptospirosis, or “lepto,” as it is commonly referred to, is a disease caused by a bacterial organism. It is a zoonotic disease, meaning it can be passed from species to species. In dogs, especially in puppies less than 6 months of age, this disease can be fatal. Leptospirosis infects the blood stream and the toxins of the bacteria attack the internal organs, which can eventually cause them to shut down and stop working. It can also cause uveitis (inflammation of the inner part of the eye) or damage to other organs.

There are many strains of bacteria that cause leptospirosis, but only eight are dangerous to dogs. These strains of lepto are passed via direct contact with the fluids of an infected animal, such as open wounds, urine, or milk. It can also be spread in utero (from mom to pups). Water can also be a source of transmission: a dog can become infected from drinking out of contaminated puddles, streams, and even water dishes.

Any age, breed, or gender of dog is at risk for lepto, but it is most dangerous for young dogs. Infected dogs often first show flu-like symptoms.


These include:

Other symptoms include:

  • Bloody urine
  • Blood in vomit or stool
  • Bruising
  • Jaundice (yellow color to mucus membranes)
  • Coughing

Your veterinarian will take a thorough history of your dog and perform a complete physical examination. They may recommend diagnostic tests to identify the cause of your dog’s symptoms.

These tests could include:

  • Chemistry tests to evaluate kidney, liver, and pancreatic function, as well as sugar levels
  • Blood parasite screening to identify if your pet has been exposed to tick-borne or other infectious diseases
  • Fecal tests to rule out intestinal parasites
  • A complete blood count (CBC) to rule out blood-related conditions
  • Electrolyte tests to ensure your pet isn’t dehydrated or suffering from an electrolyte imbalance
  • Urine tests to screen for the bacteria that causes leptospirosis and/or urinary tract infection and other disease, and to evaluate the ability of the kidneys to concentrate urine
  • A thyroid test to determine if the thyroid gland is producing too little thyroid hormone
  • Specialty tests, such as PCR testing and antibody titers

Your veterinarian will base your dog’s treatment on the severity of the clinical signs and results from diagnostic tests. Many dogs with leptospirosis require hospitalization with intensive care. The prognosis is good so long as therapy starts early and is aggressive, taking hold before major organ damage occurs. Your veterinarian will determine whether your dog requires hospitalization or not.

Talk to your veterinarian about vaccinating your dog for leptospirosis. While vaccination is not effective against all strains of the disease, it may be recommended depending on your dog’s lifestyle and the disease prevalence in your area. Keeping your dog from interacting with other infected dogs and wildlife and limiting access to potentially contaminated water sources are crucial for disease prevention.

If you have any questions or concerns, you should always visit or call your veterinarian – they are your best resource to ensure the health and well-being of your pets.