11/20/2025
The rainy season is well upon us, and it is time to talk about leptospirosis.
What is it?
Leptospirosis, or “lepto,” is caused by a bacteria that thrives in water and wet environments, where it can survive for months. We see cases year-round, but typically see an increase in the fall and winter when periods of heavy rainfall make it easier to spread.
Why is this a concern?
In the past 2 months, we have had cases every week. Unfortunately, despite our best efforts, some outcomes are devastating, and patients die.
The number of cases has increased markedly in the past decade. "Lepto" is a zoonotic disease, meaning it can also affect people. Transmission to humans is uncommon and usually seen in areas with a larger unhoused population, where exposure to contaminated rat urine occurs; a few human cases of leptospirosis acquired from dogs have been documented in Eastern Canada.
While wild animals may be a source of contamination, it is the rat population that predicts increases in cases in urban areas. Anywhere where infected urine comes into contact with a potential host for Leptospira bacteria.
Where do dogs typically come into contact with it?
The most common way dogs get leptospirosis is through water contaminated with urine, particularly stagnant or slow-moving water (think puddles, ponds, or even lakes), or through contact with urine-contaminated soil.
The bacteria can be acquired by ingestion or through breaks in the skin or mucous membranes (e.g., eyes, nose/mouth).
What does it do?
As it attaches to cells that line blood vessels, it can cause widespread damage and affect organs, most notably the liver and kidneys. The signs can vary from mild to deadly.
What are the signs?
Not very specific: fever, reduced appetite, dehydration, vomiting, diarrhea, weakness, stiffness, yellow eyes and gums (from jaundice), and diffuse bleeding (in some cases, in the lungs).
How is it treated?
The mainstay of treatment is antibiotics and symptomatic management (IV fluids for dehydration, anti-nausea medications, etc.). In more severe cases, dialysis is necessary to help the kidneys recover. We also recently acquired VetRQ, a filter that can help remove bilirubin (bile) from dogs with jaundice (liver failure).
How can we prevent it?
Vaccination with a 4 serovar vaccine is a highly effective method for preventing leptospirosis in dogs, offering significant protection against the clinical disease and reducing the risk of infection and bacterial spread.
Vaccines containing leptospiral antigen were no more reactive than other vaccines for dogs in the largest vaccine study on dogs.
Vaccinate dogs annually with the leptospirosis vaccine in our area
Limit access to standing water (don’t let them drink from puddles)
Prevent rodent problems
Please speak to your family veterinarian about the Leptospirosis vaccination
