Your dog suddenly seems lethargic, has a poor appetite or even a fever? Maybe you've just received a diagnosis of leptospirosis – or you're wondering whether there might be more behind your dog's symptoms.
In this article, I explain what leptospirosis is, how dogs become infected and what you need to look out for now.
Professionally sound – and easy to understand.

Leptospirosis is a contagious bacterial disease caused by leptospires – spiral-shaped, motile bacteria belonging to the spirochaete group. It is found worldwide and is one of the most common zoonoses, meaning it can be transmitted from animals to humans.

In Germany, leptospirosis is a notifiable disease in both dogs and humans. Due to rising case numbers in animals and people, it is now classified as a reemerging infectious disease.

The course of the disease can range from mild to chronic – or even life-threatening. Dogs of all ages and backgrounds can be affected, but young, unvaccinated dogs are considered particularly at risk.

Most cases of leptospirosis in Germany occur between July and October – during the warm and humid season, when conditions are particularly favourable for the bacteria to survive. Spring is therefore an ideal time for vaccination to ensure protection is in place in good time.

Transmission usually occurs through contaminated water or damp environments that have been soiled with the urine of infected animals – particularly rats and other rodents. The bacteria enter the body through tiny skin abrasions or mucous membranes (such as the mouth, nose or eyes).
In moist conditions and at temperatures above 18 °C, the bacteria can survive for up to three months.

• Drinking from puddles, ponds or stagnant water

• Swimming in contaminated water

• Eating infected rodents or carcasses

• Contact with contaminated soil, food, objects or sleeping areas

• Direct contact with the urine of infected dogs (rare), including through bites, mating or the placenta

Hunting dogs, retrievers, dogs in stables or rural areas, "water lovers", and dogs with free outdoor access

There are over 260 serovars, grouped into 24 serogroups. In Europe, the following serovars are particularly relevant for dogs:

• L. canicola (classic vaccine strain)

• L. icterohaemorrhagiae / copenhageni (classic vaccine strain)

• L. grippotyphosa

• L. bratislava

🧬 The clinical presentation varies depending on the serovar. For example, lung involvement is more commonly seen with infections caused by emerging serovars.

After infection, the bacteria enter the bloodstream (leptospiraemia) and spread throughout the body. They primarily target:

• Kidneys → nephritis, tubular damage, kidney failure

• Liver → liver dysfunction, jaundice, chronic hepatitis

• Lungs → coughing, pulmonary haemorrhage, difficulty breathing

• Other organs → central nervous system, spleen, reproductive organs, eyes

If left untreated, leptospirosis can lead to multiple organ failure.
Dogs may also shed the bacteria for months, even without showing symptoms (subclinical infection).

⏱️ Symptoms usually appear around 5–7 days after infection and are initially non-specific:

• Loss of appetite, fever, vomiting

• Lethargy, apathy

• Increased urination, excessive thirst

• Yellowing of the mucous membranes (jaundice)

• Bloody diarrhoea, mucosal changes

• Muscle tremors, reluctance to move

• Coughing, difficulty breathing (with lung involvement)

📍 The symptoms depend on the affected organs and the dog’s immune status. Lung involvement has been observed more frequently in eastern Germany.

• Blood and urine tests (clinical chemistry, sediment analysis, proteinuria, glucosuria)
• Serology (MAT): a titre > 1:800 or a fourfold increase is considered diagnostic
• PCR: direct pathogen detection (blood in week 1, urine from week 2 onwards)

Typical laboratory findings include:

• Leucocytosis, anaemia, thrombocytopenia

• Azotaemia, electrolyte imbalances

• Elevated liver enzymes, hyperbilirubinaemia, glucosuria

📌 PCR results may turn negative within 24 hours after starting antibiotics. Samples should therefore be taken before treatment begins.

Treatment involves a two-phase antibiotic approach:

• Penicillin / Amoxicillin (i.v.): Stops acute bacterial multiplication and shedding

• Doxycycline (oral, for 3 weeks): Eliminates the bacteria completely

Doxycycline should only be given to stable patients (no vomiting, normal liver values) and should be administered with food.

Additional supportive measures may include:

• Fluid therapy

• Pain relief and antiemetics

• Dialysis in cases of kidney failure

• Oxygen therapy in cases of pulmonary bleeding

🌟 Starting treatment early significantly improves the prognosis.

Yes – and it is strongly recommended.

• Core vaccination according to the StIKo Vet
• Protects against at least four serovars:
• • L. canicola
  • L. icterohaemorrhagiae
  • L. grippotyphosa
  • L. bratislava
• Primary vaccination: 2 doses, 3–4 weeks apart
• Booster annually, or every 6 months for high-risk dogs (e.g. hunting dogs)

Vaccination possible from 6 weeks of age

🧪 Modern vaccines also reduce urinary shedding, lowering the risk of infection for other dogs and humans.

Unfortunately, yes – even in Germany.

Around 1.5% of healthy dogs shed leptospires in their urine.

Dogs at increased risk include:

• Dogs with frequent outdoor access (woods, fields, stables)

• Dogs with contact to wildlife

• Dogs living in regions with high prevalence (e.g. northern and eastern Germany)

Even in urban areas, the risk can rise – for example, due to larger rat populations.

Leptospirosis is not a rare issue – it’s a real threat, both for your dog and for you.
But the good news is: with vaccination, awareness and timely treatment, it can be well managed.

If you have questions, are unsure or want a second opinion: talk to your vet.
Good information often helps more than you might think.

Wishing you and your pet all the best – and stay well.

Your vet, Susanne Gnass 🐾