Leptospirosis in Dogs

Contact your vet immediately Leptospirosis can cause serious liver and kidney disease and may be fatal. Seek urgent veterinary advice if your dog has possible symptoms or may have been exposed to contaminated water or urine.

Leptospirosis is an infectious disease caused by spiral-shaped bacteria called leptospires. It can affect dogs, other animals and people.

The bacteria can be found in water or warm, wet soil, including puddles, ponds, lakes, reservoirs and canals. Infection is commonly associated with the urine of infected animals, including rats, cattle and pigs.

Possible Symptoms

Dogs with suspected leptospirosis may need antibiotics, intravenous fluids and other supportive treatment. Infected dogs may need to be isolated because the bacteria can be spread through their urine.

Leptospirosis can pass to people and is sometimes known as Weil’s disease. Anyone concerned about possible human exposure should contact their doctor or consult NHS guidance.

Leptospirosis in dogs is not a notifiable disease in the UK. There is therefore no complete national figure showing how many cases are diagnosed or reported by veterinary practices.

Vaccination Information

No vaccine offers complete protection against every strain of leptospirosis. UK-authorised vaccines are intended to protect against disease caused by particular strains and may also reduce infection and urinary shedding, depending on the product.

The Veterinary Medicines Directorate states that the benefits of authorised L2 and L4 vaccines continue to outweigh their risks. Its March 2026 update describes suspected adverse events as rare.

The reported incidence was fewer than two adverse events per 10,000 animals treated with L2 products and fewer than four per 10,000 animals treated with L4 products. These are the reports received by the VMD and do not establish the total number of reactions that may have occurred. Not every suspected reaction will necessarily be reported, and receiving a report does not by itself prove that the vaccine caused the event.

Your vet can assess your dog’s individual risk by considering location, lifestyle, health and possible exposure to contaminated water or wildlife.

Read the Collielife page about Lepto 4 vaccination

Personal Guidance and Concerns

This section reflects concerns and personal views reported to Collielife. It should be considered alongside current veterinary and regulatory information.

Some owners are concerned about adverse reactions following vaccination. The decision whether and when to vaccinate should be discussed with a veterinary surgeon, taking account of the individual dog’s health, previous reactions, location and lifestyle.

When several vaccines or medicines are given during the same appointment, it may be difficult to establish which product was associated with a suspected reaction. Owners can discuss the timing of vaccinations with their vet.

If a dog becomes unwell following vaccination, contact the vet promptly. Suspected adverse reactions or a suspected lack of effectiveness can be reported to the Veterinary Medicines Directorate.

If a local case of leptospirosis has been confirmed, owners may wish to ask their vet what diagnostic test was used and, where known, which serovar was identified.

Testing

Leptospirosis can be difficult to diagnose. Testing may include blood tests, urine tests, antibody testing and PCR testing. Results must be interpreted by a veterinary surgeon alongside the dog’s symptoms, vaccination history and other findings.

Further Information

This information is not a substitute for veterinary care. Always seek advice from your veterinary surgeon about your dog’s health and vaccination requirements.