Leptospirosis in Dogs: Signs, Risks and Prevention

At a glance

What it is	An infection with Leptospira bacteria, which spread in the urine of infected animals
Who's at risk	Any dog, especially those that swim, drink from puddles, ponds or canals, hunt, or live near rats or livestock
Main signs	Fever, lethargy, poor appetite, vomiting, muscle pain, changes in drinking and weeing, yellow gums or eyes
Contagious?	Yes — through infected urine, to other animals and to people
Can it be prevented?	Vaccination reduces the risk considerably; avoiding stagnant water helps too

What it is

Leptospirosis, often shortened to "lepto", is caused by spiral-shaped bacteria called Leptospira. There are many different strains. Rats are a well-known source, but other wildlife, farm animals and dogs can also carry and shed the bacteria in their urine, sometimes without looking unwell.

The bacteria survive best in warm, wet conditions. They can live for weeks in stagnant or slow-moving water, wet soil and mud. Cases often rise after heavy rain or flooding. Dogs become infected when the bacteria enter through the lining of the mouth, nose or eyes, or through cuts and softened skin — for instance by drinking from or swimming in contaminated water, sniffing contaminated ground, or catching and eating infected rodents.

Once inside, the bacteria spread through the bloodstream. They can damage blood vessels and settle in the kidneys and liver. Some dogs develop sudden kidney failure, liver failure or both. In some, the infection causes bleeding into the lungs, which is very serious. Others have a milder illness, and a few show no signs at all yet can still shed bacteria in their urine.

Cats can be infected but rarely seem to become ill.

Signs to watch for

Signs usually appear within a couple of weeks of exposure, though this varies. They can be vague at first:

• Fever, or shivering
• Lethargy and weakness
• Loss of appetite
• Vomiting and diarrhoea, sometimes with blood
• Muscle pain, stiffness or reluctance to move
• Drinking and weeing more — or weeing much less, or not at all
• Yellowing of the gums, the whites of the eyes or skin (jaundice)
• Red, sore eyes
• Small red spots or bruises on the gums or belly, or nosebleeds
• Breathing difficulty or coughing

Because these signs overlap with many other illnesses, telling your vet where your dog has been — swimming, ditches, farmland, flooded areas or rat-prone places — can help them think of leptospirosis earlier.

When to see a vet

Contact your vet promptly if your dog is lethargic, off their food, vomiting or feverish, especially after contact with water, mud or rodents.

Treat these as an emergency:

• Yellow gums, eyes or skin
• Passing very little or no urine
• Repeated vomiting, or blood in vomit or faeces
• Unexplained bruising or bleeding
• Difficulty breathing
• Collapse or extreme weakness

Early treatment greatly improves the chance of recovery. Tell the practice when you phone that you are worried about leptospirosis, so they can take precautions to protect staff and other patients. Our guide to signs your pet needs a vet covers other emergencies.

How vets diagnose it

Leptospirosis can be tricky to confirm, so vets combine several pieces of evidence.

• History and examination, including possible exposure and vaccination status.
• Blood and urine tests to look at kidney and liver function, blood cell counts and clotting. Patterns of damage can raise suspicion.
• Tests for the bacteria or the body's response. These include tests that detect the bacteria's genetic material in blood or urine, and antibody tests. Antibody tests sometimes need repeating a week or two later, because levels rise over time and recent vaccination can affect results.
• Imaging, such as X-rays and ultrasound, to assess the lungs, kidneys and liver.

Your vet may start treatment before results come back if leptospirosis seems likely, as waiting can be dangerous.

Treatment and management

Dogs with leptospirosis usually need to be hospitalised, often in an isolation ward.

• Antibiotics to kill the bacteria and stop the dog shedding them in urine.
• Intravenous fluids to support the kidneys and correct dehydration.
• Supportive care, such as medicines to control vomiting, nutrition, pain relief and careful monitoring of urine output.
• Advanced care for severe cases. Some dogs with kidney failure need dialysis at a specialist centre, and dogs with lung bleeding may need oxygen or intensive care.

Recovery can take several weeks. Some dogs are left with lasting kidney or liver damage that needs ongoing monitoring, while others recover completely. Sadly, some dogs don't survive despite treatment, particularly when the lungs are badly affected or treatment starts late.

Protecting people

Leptospirosis is a zoonosis, meaning it can pass from animals to people. In people, it can cause anything from flu-like illness to severe disease. If your dog has, or may have, leptospirosis:

• Wear disposable gloves when cleaning up urine, and disinfect the area.
• Wash your hands thoroughly after handling your dog, their bedding or bowls.
• Keep your dog away from areas where children play, and from ponds or water others use.
• Toilet your dog in one area away from water.
• If you become unwell with fever, headache or muscle aches, see your doctor and mention your dog's diagnosis.

Your vet will advise how long precautions are needed.

Living with it

After treatment, your dog will need follow-up blood and urine tests to check how the kidneys and liver are recovering. Some dogs need a special diet or medication if their kidneys have been damaged. Make sure other dogs in the household are checked by your vet, as they may have been exposed to the same source.

Prevention

Vaccination is the most effective protection. Leptospirosis vaccines are part of the routine vaccination programme for dogs in many countries. Protection against lepto usually needs boosting more often than some other vaccines, so keep up with your vet's recommended schedule. Vaccines cover the strains most common in a given region but not every strain, so a vaccinated dog is very well protected but not completely immune.

Everyday measures:

• Discourage drinking from puddles, ponds, ditches and slow-moving water; carry fresh water on walks.
• Be especially careful after flooding or heavy rain.
• Keep rats away from your home, kennels and food stores.
• Rinse your dog off after swimming in natural water and check for cuts.

Breeds more at risk

There is no particular breed risk. Lifestyle matters most: working, hunting and gundogs, dogs that love water, and dogs in rural or rat-prone urban areas are more likely to be exposed.