Leptospirosis in dogs

Written by Dr Andrew Miller MRCVSDr Andrew Miller MRCVS is an expert veterinary working in the field for over 10 years after graduating from Bristol University. Andy fact checks and writes for Pure Pet Food while also working as a full time veterinarian. Pure Pet FoodPure Pet Food are the experts in healthy dog food and healthy dogs featured in media outlets such as BBC, Good Housekeeping and The Telegraph. Working with high profile veterinary professionals and nutritionists, Pure Pet Food are changing dog food for the better. - Our editorial process

Leptospirosis, sometimes shortened to Lepto, is a serious disease in dogs and it is one of several illnesses you might be asked to consider vaccinating against when you first bring your puppy home. It isn’t as common as other diseases like Parvovirus, but it can still be potentially fatal or cause lasting organ damage if your dog becomes infected.

Lepto can affect any dog of any breed or age, and the symptoms can sometimes go unnoticed in mild cases. That’s why it’s im-paw-tent for pet paw-rents to understand what Leptospirosis in dogs is, how it can affect your pooch, and how it can be prevented.


Leptospirosis in dogs is a serious disease caused by a bacteria called Leptospira or Leptospires.

Leptospires can be found in soil and water throughout the UK, and can enter your dog’s body through their mouth, nose, or wounds. Once inside the body, the bacteria travel through your dog’s bloodstream to colonise in the liver and kidneys.

There are 250 known strains of Leptospira bacteria found throughout the world, with some being far more common than others. There are 4 main strains that are known to commonly infect dogs in the UK and Europe.

If your dog is infected, the disease will affect a number of their internal organs and often causes considerable damage to their liver and kidneys, where the bacteria colonise. Leptospirosis can often be fatal if a dog suffers from liver or kidney failure as a result of infection.

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Some dogs will be able to fight off the infection within 10 days provided they have a strong immune system, receive prompt treatment and supportive care from a veterinarian. However, even the dogs that survive can be left with chronic liver or kidney disease which will affect them for life.


Leptospires, the bacteria which can cause Leptospirosis, are present throughout the UK. These bacteria can live in damp soil and water for months, and any waterway or area of wet ground can be contaminated.

If your dog is known to go swimming in ponds or rivers, they could accidentally ingest the bacteria by swallowing or inhaling a little water. The bacteria can also enter your dog’s body through any wounds or broken skin they have. That means even if your dog just swims or walks through infected water or soil with a cut on their paw, there is the potential that they may become infected.

Other animals can spread Leptospirosis too, and most mammals can be infected and spread Leptospires. Rats and other rodents are the most common carriers of this disease, however other mammals like cows, foxes and other dogs can also carry the disease and shed the bacteria in their urine.

Leptospirosis is spread through the urine of infected animals. Your dog needs only to sniff or lick some urine from another contaminated animal and they too can become infected.

Cats can become infected with Leptospirosis but they rarely show any signs of illness and seem more resistant to Lepto. Worryingly, humans can contract Leptospirosis as well.

Your dog doesn’t need to directly lick infected urine either, because the Leptospira bacteria can live in the soil for several months. If your dog eats, licks, or even sniffs soil that has been contaminated by infected urine, they can still become infected themselves.

Even if your dog somehow only goes outside in your own back garden, there is still the chance an infected mammal like a fox or rodent will at some point enter your yard and urinate there, so there is still a small risk of coming into contact with Leptospira bacteria even if they never leave your garden.

Because Leptospires are found throughout the country and can be carried by many different animals, as well as being able to survive for months in soil or water, your dog could contract Leptospirosis anywhere in the country at any time.


There are few reports on the incidence rates of Leptospirosis in dogs in the UK. The disease can be tricky to diagnose, and there is speculation as to whether it is clinically underreported.

retrospective study of almost 2 million dogs in America and Canada found an incidence rate of 37 cases per 100,000 dogs. Meanwhile, a more recent study in Switzerland reported a peak of 28.1 cases per 100,000 dogs.

Here in the UK, we have a better idea of how prevalent Leptospirosis is in the human population. There were 50 cases in humans in 2013, 23 acquired natively and 2 of which were fatal. 24 other cases were people infected abroad. The UK usually has fewer than 80 cases of Lepto in humans each year, and a significant number of these cases are contracted abroad.

As you can see, there are few cases of Lepto each year, but that is in part due to the efficacy of vaccination in dogs. And it’s im-paw-tent to remember that although your dog’s chances of catching the disease are small, the chance of it being fatal should they become infected is quite high.

You can discuss your individual dog’s needs and risks of Lepto with your vet, and they’ll be able to inform you on cases in your area, prevention, and how appropriate vaccination would be according to your individual case.


Humans can become infected with Leptospirosis, which is called Weil's Disease. People usually become infected in the same ways dogs are, by coming into contact with infected soil, water, or urine. The bacteria can enter the body through the mouth, nose, or a break in the skin. Humans can catch Leptospirosis from infected animals, including dogs, if they come into contact with their urine or blood.

Leptospirosis is one of the most common zoonotic diseases in the world, but it’s very rare for humans to catch Lepto from their pets. Although the chance of catching Lepto from your pooch is small, you should exercise caution and minimise the risk to yourself by always washing your hands after touching an infected pet, and making sure you do not come into contact with their urine. If you need to clean up your dog’s urine for any reason, wear gloves and clean the area with disinfectant, then thoroughly wash your hands afterwards.

Children as well as anyone who is pregnant or has a compromised immune system should avoid contact with an infected dog until the dog is no longer shedding bacteria in their urine, or once the person is at lower risk of serious infection.

If your dog displays symptoms of Leptospirosis or is known to be infected and you become unwell yourself, you must contact your GP or call 111 for advice.


Some cases of Leptospirosis can be very difficult to detect, and a dog might display little to no symptoms of illness whilst still carrying and spreading the disease. Other cases can be severe and may even prove fatal.


Some symptoms are more associated with a particular form of Leptospirosis. These forms include renal, jaundice, or hemorrhagic. Out of these, jaundice or any case displaying liver dysfunction are associated with a higher mortality rate.

Symptoms of renal Leptospirosis include:

  • Increased thirst

  • Increased urination

  • Ulcers on the tongue

  • Kidney failure

Symptoms of hemorrhagic Leptospirosis include:

  • Blood in your dog’s urine

  • Blood in your dog’s poo

  • Bloody vaginal discharge

  • Bloodshot eyes

  • Bleeding in the mouth

Symptoms of jaundice Leptospirosis include many of the symptoms for hemorrhagic Leptospirosis, such as blood in the urine. Additional symptoms of the jaundice form include:

  • Yellow mouth

  • Yellow in the whites of your dog’s eyes

  • Yellow skin

If your dog shows any signs of Leptospirosis and you believe they may be infected, take care not to touch their urine and contact your vet as soon as possible.


Unless you keep your dog in the house 24/7, there’s always going to be a small chance that they will come into contact with Leptospires and paw-tentially become infected with it.

Preventing your dog from swimming in natural water or drinking from puddles or other outdoor water sources should minimise their risk of infection. However, the most effective method of prevention is vaccinating your pup against Leptospirosis.


Vaccinating against Leptospirosis isn’t mandatory, but it is considered one of the most im-paw-tent vaccines your dog can have. It’s a core vaccine as outlined by The British Small Animals Veterinary Association (BSAVA) due to its im-paw-tence in preventing serious disease.


Leptospirosis vaccines contain inactive cells of Leptospires which are injected into your dog. Because the cells are inactive, they cannot infect your dog with the disease, but their body can learn how to fight the specific bacteria and prevent infection.

The vaccines work because your pooch’s body recognises these inactive cells as potentially dangerous foreign particles, and their immune system responds to fight them off. Their body will begin to produce T Cells which are like a specialist fighter team designed to combat and destroy a specific threat, in this case, Leptospires. In short, their immune system destroys the inactive cells and learns how to fight them off, all without being at risk of disease or organ damage.

Immunity from these vaccines does wear off over time, and your pooch will need yearly booster jabs to make sure their body doesn’t forget how to make those Lepto-fighting T cells.


Vaccinating your dog will dramatically reduce their risk of developing Leptospirosis if they become infected by the bacteria, and it lowers their chance of serious illness or death.

In one study, 14.61% of responding vets had seen a case of Leptospirosis in the last 12 months, and 60% of cases were fatal for the infected dogs, highlighting just how common and serious this disease can be. Within the same study, all but 1 case of Leptospirosis were in unvaccinated dogs, indicating the effectiveness of the vaccine in preventing dogs from developing the disease even after contact with Leptospira bacteria.

It is im-paw-tent to vaccinate your dog and keep up to date with their boosters because it prevents ill health and could save their life. Not only does vaccinating your dog protect their own health, but it also protects the animals and humans around them.

Vaccination will prevent your dog from carrying the disease, which means they won’t be able to infect other animals or humans. In areas where vaccine uptake is high and dogs have increased immunity, cases of Leptospirosis are very rare.


There are numerous different strains of Leptospirosis bacteria here in the UK, and each vaccine protects against some of the most common strains. An L2 vaccine means that it is designed to protect against 2 different groups of Lepto bacteria, while an L4 vaccine protects your pooch against 4 different groups.


Yes, both the L2 and L4 vaccines are paw-fectly safe for the majority of dogs. Just like anything your dog comes into contact with be it food or medicine, there is a very small risk they might have a reaction to the vaccine, but it is very rare.

The incidence rate is so small that for every 10,000 L2 vaccines used, fewer than 2 dogs have any adverse reactions. The incidence rate is slightly higher for the L4 vaccine, but still very small as fewer than 7 dogs have an adverse reaction to the vaccine per 10,000 vaccines used.


Some dogs are more at risk of contracting Leptospirosis due to where they live, and what their lifestyle is like. Dogs that could be at higher risk of infection include:

  • Dogs that wade or swim in outdoor water sources

  • Dogs that drink from puddles, lakes, rivers, and outdoor water sources

  • Dogs living in areas exposed to flooding

  • Dogs living in rural areas

  • Dogs living in areas with high rainfall

  • Working farm and hunting dogs

In one study of Leptospirosis incidence and risk factors, Cocker Spaniels, Collies, and Lurchers had an increased rate of diagnosis of Leptospirosis compared to the average doggy pup-ulation.

More cases of Leptospirosis are reported in the colder, wetter months. This is because Leptospires can survive for months in water, but are destroyed by warm temperatures.

Meanwhile, although puppies and dogs with health conditions are not at higher risk of contracting the disease, they are at greater risk of serious illness or death should they be infected. This is due to the fact they have developing immune systems or compromised immune systems that cannot fight off the infection as effectively as a healthy, adult dog.


Diagnosing Leptospirosis in dogs can be tricky as the symptoms are shared with many other diseases, and some dogs may only show mild illness at first. However, if your pooch is unvaccinated and displaying a fever and symptoms of kidney or liver dysfunction, then your vet is likely to suspect Lepto. They might ask you a few questions about your dog’s symptoms, recent activity, and any incidents that might have caused the condition.

Your vet may conduct a PCR test on a sample of your dog’s blood or urine to look for the presence of Leptospira bacteria. Alternatively, they might inspect samples of body fluids from your dog to assess the number of antibodies they are producing.


If you suspect your dog has Leptospirosis they will need to be taken to the vet for testing and urgent care. If they are diagnosed with the disease, they will be treated separately from other animals and kept in isolation to prevent the disease from spreading to other pets and human staff.

Treatment for Leptospirosis in dogs with mild cases will include a course of antibiotics, which is often enough to clear the infection in mild and early cases of the disease.

Otherwise, treatment for Leptospirosis is largely supportive. This will include an intravenous drip to keep your dog hydrated and to help support their liver and kidneys. A drip will also carry medicines into their system, including painkillers. Your dog may be given antiemetics to prevent nausea and vomiting. Some dogs might require a blood transfusion if they have suffered from haemorrhaging, and some animals require oxygen. Regardless of treatment, it is likely your dog will be in the veterinary hospital for a few days under observation.

Sadly, if your dog suffers from severe illness you may be asked to consider euthanasia due to the extent of the damage to their internal organs and based on their chances of survival, as well as the impact it will have on their ongoing wellbeing.

For dogs that respond well to treatment and survive, they can still suffer from persistent liver or kidney damage. They will also continue to carry and spread the Leptospira bacteria in their urine for a long time after infection, meaning they can still infect other animals or people.


If you own several dogs and one is being treated for Lepto, your other pups might be tested or treated with antibiotics as a precaution. You might also want to consider having your human family members tested for the disease.

When your pooch is home from the animal hospital, your vet will probably advise crate rest. It’s im-paw-tent your dog is given plenty of time to rest and not putting their body under any undue strain from exercise until they have recovered.

Any time your dog vomits, urinates, or defecates, you must clean the area with disinfectant and ideally wear a mask and gloves. You should also wear gloves when handling your dog, and wash your hands thoroughly after touching them or any of their bodily fluids.


The rate of recovery and lasting impact of Leptospirosis in dogs varies dramatically. Some dogs will only show mild illness and make a near-complete recovery, while others may recover but suffer from chronic liver or kidney disease as a result of the damage to their organs. Sadly, a significant proportion of dogs who contract Leptospirosis will die.

If you have an adult dog with a strong immune system and the disease is diagnosed early and treated promptly, they have a decent chance of survival.

  1. Incidence and demographic risk factors for leptospirosis in dogs in the UK The Royal Veterinary College, May 2021, doi.org/10.1002/vetr.512
  2. Leptospira cases and vaccination habits within UK vet-visiting dogs The Veterinary Record, Feb 2014,doi:10.1136/vr.102085
  3. VMD position paper on authorised vaccination schedules for dogs Veterinary Medicines Directorate, PDF
  4. Leptospirosis (Weil's disease) NHS
  5. Zoonoses World Health Organisation, July 2020
  6. Leptospirosis and Weil’s disease in the UK An International Journal of Medicine, 105, (12), Dec 2012, 1151–1162, doi.org/10.1093/qjmed/hcs145
  7. Increasing Incidence of Canine Leptospirosis in Switzerland Department of Clinical Veterinary Medicine, 11, (7), July 2014, 7242-7260, doi.org/10.3390/ijerph110707242
  8. Prevalence of and risk factors for leptospirosis among dogs in the United States and Canada: 677 cases (1970–1998) Journal of the American Veterinary Medical Association, 220, (1), Jan 2002, 53-58, doi.org/10.2460/javma.2002.220.53