If you walk your dog past parks, canals or puddles this winter, there is one uncommon but deadly bacterial disease worth knowing about: leptospirosis. It is caused by Leptospira bacteria and spreads mainly through the urine of rats and other rodents. The RSPCA notes that infected dogs can go on to develop kidney failure, liver failure and, less often, serious lung disease. Cold, wet weather can push rats closer to homes, sheds and bins, and the bacteria can survive for months in soil and standing water when conditions suit them. The good news is that a few simple habits, and for some dogs a vaccine, sharply cut the risk.
The Sydney cases that changed the advice
Canine leptospirosis was long seen in Australia as an uncommon disease of warmer, wetter regions. That shifted after a cluster of cases in inner Sydney. A University of Sydney case series documented 17 confirmed cases in the Greater Sydney area between 2017 and 2020, 13 of them within the City of Sydney, with a case fatality rate of 88% from severe liver and kidney disease. Cases turned up in suburbs including Surry Hills, Darlinghurst, Redfern, Glebe, Newtown and Paddington, dense inner-city areas rather than farmland.
The same research found Leptospira in roughly 29% of rats sampled in the City of Sydney in 2020, with brown and black rats as the reservoir and serovar Copenhageni the type found in most of the dogs tested. In other words, the risk followed the rats into the city. The RSPCA now lists Sydney, Newcastle and the South Coast among at-risk areas. The RSPCA reports that in NSW outbreaks between 2017 and 2022, more than 70% of infected dogs died.
How dogs catch it
Dogs become infected when the bacteria enter through the mouth, eyes, nose or a break in the skin, usually after contact with infected urine or contaminated soil and water. Sniffing or drinking from puddles, ponds and stagnant water, hunting rodents, or nosing around rubbish and compost where rats gather are the classic exposures. Rodents are the most common carriers and shed the bacteria in their urine. This is why wet weather matters: rain and local flooding wash contaminated urine into puddles and low-lying ground, and cold snaps push rodents closer to homes and sheds in search of food and shelter. Moist conditions also help the bacteria survive in the environment.
Symptoms to watch for
Early signs are vague and easy to miss. The RSPCA and Sydney specialist hospital SASH both list fever, lethargy, loss of appetite, vomiting, diarrhoea, increased drinking and urination, and jaundice (a yellow tinge to the gums, skin or the whites of the eyes). Because the bacteria can hit the liver, kidneys and lungs at once, signs vary a lot from dog to dog, and a dog can go downhill fast.
| Sign | What to do |
|---|---|
| Mild off-day: slightly quiet, ate a bit less, otherwise bright | Monitor closely for 12 to 24 hours and phone your vet for advice |
| Yellowing of the gums, skin or eyes (jaundice) | See a vet the same day, possible liver involvement |
| Vomiting or diarrhoea with lethargy and no appetite | See a vet the same day, especially after wet-weather walks |
| Drinking and urinating much more, or barely urinating | Urgent, possible kidney involvement |
| Difficulty breathing, coughing blood, collapse | Emergency, go to the nearest vet or emergency hospital now |
Vets confirm the diagnosis with blood tests, urine tests and PCR. Caught early, many dogs respond to antibiotics; severe cases may need hospitalisation with intravenous fluids and, at referral centres, dialysis. SASH reports survival above 50% with appropriate treatment, and above 80% when specialists can provide dialysis, but prevention is far kinder than the alternative. This is general information only; consult a licensed veterinarian for diagnosis or treatment specific to your pet.
Is your dog at higher risk?
In Australia, leptospirosis is most common in north-eastern NSW and Queensland, and human and canine outbreaks are often linked to flooding. But the Sydney cluster shows city dogs are not immune. Most Australian dogs are low risk, but some clearly are not. Your dog is at higher risk if it:
- Hunts, catches or chases rats and mice
- Drinks from or swims in puddles, ponds, canals or stagnant water
- Lives near waterways, bushland, farms, livestock or areas with a known rat problem
- Walks in areas recently affected by flooding or heavy rain
- Lives in or visits regions where cases have been reported, such as Sydney, Newcastle and the NSW South Coast, or the warmer, wetter parts of north-eastern NSW and Queensland
Prevention and the vaccine
A few practical habits do most of the work:
- Keep your dog on a lead near water and discourage drinking from puddles or stagnant ponds
- Control rodents around the home: secure bins, clean up fallen food and clutter, and cover compost
- Check roofs, sheds and garages in cold weather, when rats may move in, and avoid leaving pet food out overnight
- Avoid loose rat baits: they poison dogs directly and do not remove the leptospirosis risk. See our guide to rat-bait poisoning in dogs and cats
- Wash your hands after handling anything a rodent may have soiled
There is also a vaccine. When the University of Sydney study was published in 2022, Australia had one registered monovalent leptospirosis vaccine (Protech® C2i, Boehringer Ingelheim), which targets serovar Copenhageni, the type behind the Sydney cases. It is not part of the standard C3 core vaccination in Australia and is usually given as an optional extra, so you may need to ask for it. The RSPCA and the 2024 WSAVA vaccination guidelines recommend it for dogs in at-risk areas or with rodent, livestock or stagnant-water contact. The course is two doses two to four weeks apart, then a yearly booster. Many clinics offer it as an optional add-on to the annual vaccination; prices vary, so ask your vet how it fits with your dog’s existing vaccination schedule and costs. Winter is also a sensible time to review overall parasite and preventative-health protection.
Can people catch it from their dog?
Yes, leptospirosis is zoonotic. NSW Health and Victoria’s Better Health Channel explain that people can be infected through contact with the urine of infected animals, or with contaminated water or soil, usually via cuts or the eyes, nose and mouth. In people, symptoms often come on suddenly with fever, headache, muscle aches and chills. Direct dog-to-owner spread is uncommon, but if your dog is diagnosed, wear gloves when cleaning up urine, wash your hands well, and tell your own doctor about the exposure.
Frequently asked questions
Is leptospirosis common in Australian dogs?
No. It remains uncommon, and is concentrated in north-eastern NSW and Queensland and in flood-affected areas. But recent inner-Sydney cases show the picture is changing, and when dogs are infected the disease is often severe.
Does my dog need the leptospirosis vaccine?
It depends on where you live and what your dog does. It is generally recommended for dogs with rodent, livestock or stagnant-water exposure, or in areas where cases have occurred. Your vet can weigh your dog’s risk against the local situation.
Can leptospirosis be cured in dogs?
Many dogs recover with prompt antibiotics and supportive care, and survival can exceed 50% with treatment. The catch is that early signs are easy to miss, so fast veterinary attention matters.
Key takeaways
- Leptospirosis is uncommon in Australian dogs but can be fatal; NSW outbreaks have killed most infected dogs
- It spreads through rodent urine and contaminated water; wet weather and rats near the home raise the risk
- Watch for fever, vomiting, lethargy, jaundice and changes in drinking or urination, and act fast
- Keep dogs on a lead near water, control rodents, and skip loose rat baits
- Ask your vet whether the Protech C2i vaccine suits your dog’s risk
- It is zoonotic, so take hygiene precautions if your dog is diagnosed
About the author. GoPetr Writer writes about companion-animal care for GoPetr. We are not veterinarians, and this article is general information only, not a substitute for veterinary advice. Every health claim above is linked to an Australian veterinary, welfare or government source. Always consult a licensed veterinarian for advice specific to your pet.
