Weil's disease in dogs: symptoms, treatment and prevention

Weil’s disease, also known as leptospirosis, is a serious bacterial infection that affects dogs and is transmitted through contact with contaminated water or infected animals. This disease, caused by Leptospira bacteria, can lead to kidney failure, liver damage and severe bleeding. Symptoms range from mild fever to life-threatening organ damage. Prompt treatment with antibiotics and supportive care increases the chances of survival. Vaccination offers protection, but does not prevent all subtypes. Preventing infection by avoiding contact with stagnant water and rodents is essential. In this article, you can read about the symptoms, treatment options and preventive measures to protect your dog.

What are the symptoms of Weil’s disease in dogs?

The symptoms of leptospirosis vary from dog to dog and depend on the severity of the infection and the organs affected. Here are the most common signs:

• General symptoms: Fever, loss of appetite, lethargy, weight loss and muscle weakness.
• Gastrointestinal symptoms: Vomiting, diarrhoea (sometimes with blood), abdominal pain and dehydration.
• Kidney and liver problems: Jaundice (yellowing of the skin/eyes), frequent or reduced urination and dark urine.
• Serious complications: Pneumonia, coughing, shortness of breath and bleeding in the mucous membranes or skin.
• Muscle and joint pain: Stiffness, difficulty moving and muscle tremors.

How soon do symptoms appear after infection?

Symptoms appear within 4 to 12 days of infection, but some dogs remain asymptomatic for a long time whilst the bacteria cause organ damage [1].

What are the consequences of untreated leptospirosis?

Untreated cases lead to kidney and liver failure and can cause bleeding or shock. In dogs that go on to develop the most severe form, leptospiral pulmonary haemorrhage syndrome, mortality has been reported as high as 70% [1][2].

How is Weil’s disease treated in dogs?

Treatment must be started immediately after the first symptoms appear to prevent complications. This includes:

1. Antibiotics: Doxycycline or penicillin helps to combat the infection. A full course of treatment is necessary.
2. Intravenous fluids and supportive care: Helps maintain kidney function and prevent dehydration.
3. Symptomatic treatment: Anti-sickness medication and treatment for liver or kidney failure.
4. Hospitalisation and quarantine: Prevents further spread, particularly in dogs that come into contact with other animals.

How effective is the treatment?

With prompt diagnosis and treatment, most dogs recover, and reported survival to hospital discharge ranges from around 75% up to over 80% with intensive care such as dialysis. Organ damage can still be permanent even in dogs that pull through [1][2].

Can a dog recover without treatment?

Dogs with a mild infection may recover on their own, but are at increased risk of permanent kidney damage or becoming chronic carriers.

How can Weil’s disease be prevented in dogs?

The most effective preventive measures are:

1. Vaccination against leptospirosis

Annual vaccination prevents serious infections, but does not offer 100% protection against all Leptospira strains. A 2022 meta-analysis of commercial vaccines found around 84% protection against clinical disease and 88% against dogs becoming silent kidney carriers [3].

Vaccine	Leptospira strains covered	Are boosters needed?
L2	Leptospira canicola, Leptospira icterohaemorrhagiae	Yes, annually
L4	L2 + Leptospira grippotyphosa, Leptospira australis	Yes, annually

2. Avoid contact with high-risk areas

• Avoid stagnant water (puddles, ponds, mud).
• Avoid areas with high rodent populations.
• Do not allow dogs to drink rainwater from unhygienic sources.

3. Hygiene measures

• Wash your hands after coming into contact with other dogs’ urine.
• Clean drinking bowls and living areas regularly.
• Prevent dogs from sniffing at carcasses.

How effective is the leptospirosis vaccine?

It meaningfully reduces the risk of serious infection and kidney carriage, but protection is largely limited to the serogroups included in the vaccine, so it is not completely effective against every strain of the bacterium [3]. Immunity also fades over roughly a year, which is why annual boosters matter.

How is leptospirosis diagnosed in dogs?

The diagnosis is made using a combination of clinical symptoms and laboratory tests:

1. Blood test: Shows elevated liver and kidney values.
2. Urine test: Detects the presence of Leptospira bacteria.
3. Serological test (antibody test): Assesses exposure to the bacteria.
4. PCR test: A highly accurate test to detect Leptospira genetic material.

How reliable are the tests?

PCR tests detect active infections, whilst serological tests indicate whether a dog has been exposed in the past. A single antibody titre can be hard to interpret on its own, so vets often recheck it one to two weeks later to see whether it has risen [1].

Can a dog transmit Weil’s disease to humans or other animals?

Yes, leptospirosis is zoonotic, meaning that humans and other animals can become infected. A 2024 US public health report described a person who fell ill during a canine leptospirosis outbreak after occupational contact with affected dogs, a reminder that this isn’t just a veterinary concern [4].

How can an infected dog spread leptospirosis?

• Through urine, saliva or contaminated water.
• Through direct contact with wounds or mucous membranes.
• Via contaminated surfaces such as food bowls or floors.

How can owners protect themselves against leptospirosis?

• Wear gloves when handling infected dogs.
• Clean urine and living areas thoroughly with disinfectants.
• Avoid direct contact with blood and saliva.

What are the risk factors for leptospirosis in dogs?

Certain situations increase the risk of infection, including:

1. Living in a damp environment: Dogs in rainy areas are at greater risk.
2. Hunting dogs or dogs that swim: Contact with infected water is a common route of transmission.
3. Urban areas with rodents: Rats and mice are major carriers of Leptospira.

Are certain breeds more susceptible to Weil’s disease?

No, any dog can become infected, but young dogs and dogs with a weakened immune system often experience more severe symptoms.

Can dogs suffer lifelong damage after infection?

Yes. Some dogs develop chronic kidney or liver problems after recovering from acute leptospirosis, even once the bacteria itself is gone [1][2].

Which organs may be affected following infection?

• Kidneys: Reduced kidney function can lead to chronic kidney disease.
• Liver: Fibrosis or scarring may occur.
• Lungs: Severe cases cause permanent lung damage.

How can owners minimise long-term health damage?

• Regular monitoring of blood and urine values after recovery.
• A healthy diet to support the kidneys and liver.
• Reducing physical stress in dogs that have suffered a severe infection.

Conclusion

Weil’s disease in dogs is a potentially life-threatening bacterial infection with symptoms ranging from fever and vomiting to severe kidney and liver damage. Early diagnosis and treatment with antibiotics significantly improve the chances of survival. Vaccination offers protection, but it isn’t 100% effective and needs repeating every year. Prevention comes down to a few unglamorous habits: steering clear of stagnant water and rodents, and staying alert to early symptoms. Keep vaccinations current, and don’t wait out a fever that doesn’t seem to be lifting.