The first symptoms of leptospirosis in dogs are often vague: fever, lethargy, and loss of appetite. These signs typically appear within 2 weeks of exposure and can look like dozens of other illnesses, which is what makes leptospirosis dangerous. Within just a few days, the infection can progress to kidney failure, liver damage, and life-threatening bleeding. Knowing what to watch for, and how quickly things can change, gives you the best chance of catching it early.
Early Signs You Might Notice First
The initial phase of leptospirosis is frustratingly nonspecific. Your dog may simply seem “off” for a day or two before more telling symptoms develop. According to the CDC, the earliest signs include:
- Fever
- Lethargy (reluctance to move, sleeping more than usual)
- Depression (withdrawn behavior, lack of interest in play)
- Loss of appetite
- Joint or muscle pain (stiffness, flinching when touched)
- Eye and nasal discharge
- Changes in urination (peeing more or less than normal)
At this stage, bloodwork may not yet show organ damage. That’s a problem, because the window between “seems a little sick” and “critically ill” can be just a few days. Dogs that are unvaccinated against leptospirosis and develop a sudden fever with any of these signs warrant immediate veterinary attention, especially if they’ve recently been around standing water, wildlife areas, or flooded environments.
Kidney and Liver Symptoms
Leptospirosis targets two organs above all others: the kidneys and the liver. As the bacteria multiply, dogs typically develop signs of acute kidney injury first, followed by or alongside liver dysfunction. This is the phase where the disease becomes unmistakable and dangerous.
Kidney-related symptoms include dramatic changes in urination. Some dogs drink and urinate far more than normal as the kidneys lose their ability to concentrate urine. Others stop producing urine almost entirely, which signals the kidneys are shutting down. Vomiting, dehydration, and back pain from swollen kidneys often follow. In one documented case of a 6-year-old American bulldog, the dog went from reduced urination to producing no urine at all within a single night of hospitalization.
Liver involvement shows up as jaundice, a yellowing of the whites of the eyes, gums, and skin. This happens because damaged liver cells can no longer process bilirubin, the yellow pigment normally cleared from the bloodstream. Jaundice is one of the more recognizable signs for dog owners and tends to appear within the first few days of illness. Abdominal pain, particularly when the belly is pressed on, is another hallmark. Some dogs develop diarrhea, sometimes with blood.
Bleeding and Bruising
Leptospirosis can cause a drop in platelets, the blood cells responsible for clotting. When platelet counts fall low enough, dogs may develop unusual bleeding that has no obvious cause. This can show up in several ways:
- Petechiae: tiny red or purple dots on the gums, belly, or inner ears
- Nosebleeds
- Blood in urine or stool
- Bruising (purple patches under the skin)
- Vomiting blood
Among dogs that died from confirmed leptospirosis in one study, low platelet counts were present in half the cases. If your dog is bruising easily or you notice blood where there shouldn’t be any, that’s an emergency sign regardless of the cause.
Respiratory Signs
One of the more surprising symptoms of leptospirosis is lung involvement. Some dogs develop rapid breathing, coughing, or difficulty breathing due to hemorrhage in the lungs. This pulmonary form of the disease can look like pneumonia and is sometimes the most prominent symptom, even overshadowing kidney or liver failure. Coughing up blood, while less common, is a recognized sign. Veterinary guidelines specifically flag pulmonary hemorrhage alongside kidney and liver damage as a hallmark combination that should raise suspicion for leptospirosis.
Eye Problems
Leptospirosis can cause inflammation inside the eye, known as uveitis. You might notice your dog squinting, with red or watery eyes, or eyes that appear cloudy. Conjunctivitis (redness and swelling of the tissue around the eye) and tiny hemorrhages on the back of the eye are also documented. These signs are easy to dismiss as a minor eye infection, but in the context of a sick dog, they point toward a systemic illness spreading through the bloodstream.
How Quickly Symptoms Progress
Speed is what sets leptospirosis apart from many other canine infections. The disease typically moves through two phases. The first phase brings that nonspecific fever and malaise as the bacteria circulate through the bloodstream. Within days, the second phase begins as the bacteria settle into the kidneys and liver, and organ damage accelerates.
The updated consensus statement from the American College of Veterinary Internal Medicine notes that leptospirosis “can progress rapidly to acute kidney injury,” and the clinical window for the entire illness, from first vague symptoms to severe organ failure, fits within about 2 weeks. Some dogs deteriorate much faster. The vomiting, dehydration, and back pain from kidney failure that the CDC describes as “within a few days” of initial symptoms is consistent with what veterinarians see in practice.
What Veterinarians Look For
Because early leptospirosis looks like so many other illnesses, vets rely on a combination of symptoms, bloodwork, and specific tests. The pattern that raises the biggest red flag is sudden kidney problems appearing alongside liver abnormalities or lung hemorrhage, especially in a dog that isn’t vaccinated against leptospirosis.
Bloodwork typically reveals markers of kidney damage, elevated liver enzymes, and sometimes evidence of pancreatic inflammation. Two specific tests confirm the diagnosis. A PCR test detects the bacteria’s genetic material directly, often from blood or urine. An antibody test (called a MAT) measures the immune response. Neither test alone catches every case, because the bacteria appear in the blood early in the disease while antibodies develop later. Running both tests together gives the most accurate picture, particularly in the first days of illness when results can go either way.
Survival and Prognosis
How a dog fares with leptospirosis depends heavily on how quickly treatment begins and how much organ damage has occurred. A study published in Open Veterinary Journal found that dogs with confirmed active infections had a mortality rate of about 59%, with leptospirosis-related deaths occurring at a median of 27 days after diagnosis. Among dogs that died, the most common complications were anemia, kidney failure, elevated white blood cell counts, low platelets, and jaundice.
Dogs that receive aggressive supportive care early, including fluids, antibiotics, and management of kidney function, have significantly better outcomes. The same study found that dogs without active infection at the time of testing had longer survival times overall, with a median survival exceeding 400 days. The takeaway is straightforward: the earlier leptospirosis is caught and treated, the better the odds. Dogs that are still in the initial fever-and-lethargy phase have a much wider treatment window than those already in kidney or liver failure.
Signs That Overlap With Other Illnesses
Part of what makes leptospirosis tricky is that its symptoms, taken individually, mimic other common conditions. Vomiting and diarrhea look like a dietary problem or parvovirus. Lethargy and fever could be a tick-borne illness. Jaundice might suggest a bile duct obstruction or toxin exposure. Even the kidney failure can resemble antifreeze poisoning or other causes of acute kidney injury.
The combination of symptoms is what points toward leptospirosis specifically. A dog that develops sudden kidney problems plus jaundice plus fever, or kidney failure with unexplained bleeding and lung issues, fits the profile much more clearly than one with an isolated symptom. Vaccination status matters too. While leptospirosis has been reported even in vaccinated dogs, the current veterinary consensus is that other diagnoses should be considered more likely in dogs that are up to date on their four-strain leptospirosis vaccine.