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What is it?

Leptospirosis is a disease caused by spiral shaped bacteria of the Leptospira group. These can infect all mammals - including humans. The bacteria can be transmitted directly through the urine of infected animals (most commonly rats and other rodents, but occasionally infected dogs and other animals) and indirectly through contaminated soil/water.

Why is it important?

It is a zoonotic disease meaning humans can become ill from infected animals. In fact, it is considered one of the most common zoonotic diseases worldwide. There are also different types of the bacteria, some of which cause more serious illness than others. Some can even result in death of affected dogs and, rarely, infected humans.

What’s the risk?

Any dog of any age can become infected if exposed to the bacteria. The bacteria prefer warm, humid conditions resulting in a seasonal increase in cases during warmer months and when flooding has occurred.

What happens to the animal?

After infection with the bacteria it can spread via the blood to almost any site in the body. As leptospirosis can affect many organs, symptoms vary greatly and are not specific to this disease alone. Possible signs include:

  • Fever
  • Decreased appetite
  • Vomiting/Diarrhoea
  • Lethargy/Weakness
  • Pain
  • Abnormal breathing
  • Unusual bleeding/bruising
  • Jaundice (yellowing of the skin/eyes)
  • Altered urine output
  • Weight loss
  • Halitosis
  • Uveitis/conjunctivitis (inflammations of the eye)
  • Mild forms of the disease may present as a short-term general ill health. More severe forms can result in multi-organ damage, in particular to the liver, kidneys and lungs.

    How do you know what’s going on?

    Routine blood tests are non-specific but may increase your vet’s suspicion about leptospirosis. They may show anaemia, increases in some types of white blood cells and decreased platelets. Damage to the kidneys can also cause abnormal salt (electrolyte) levels and both kidney and liver damage cause characteristic blood changes. Urine samples may show signs of blood, glucose (sugar) and protein as the kidneys become damaged and start to leak. Imaging with x-rays and/or ultrasound can show damage to organs but is non-specific.

    If your vet is suspicious of leptospirosis then blood, urine or tissue samples (biopsies) can be sent to the laboratory to check for DNA traces of the Leptospira bacteria’s DNA. Alternatively it is possible to look for antibodies (the body’s defence response) against leptospirosis using a blood sample. However, as it takes time for the body to respond to infection this test can sometimes be negative early-on and need repeating after 1-2 weeks.

    What can be done?

    Antibiotics targeted against the bacteria are given to clear the infection and hopefully prevent further organ damage. Doxycycline is often the antibiotic of choice as it clears infections better from the kidneys than other antibiotics. However, sometimes penicillins are used initially to stabilise a patient before using doxycycline, especially when the dog has gastro-intestinal symptoms.

    Other medications to help with symptoms and support organ function may also be given along with fluid therapy (usually as a drip). Dogs are usually hospitalised to give this supportive care until their symptoms are well controlled and organ function has improved. Kidney function can take several months to improve after the infection is cleared, and even then around 50% of surviving dogs still have decreased kidney function after 1 year and require life-long monitoring.

    How can I protect my pet?

    Vaccination protocols exist to protect dogs from this disease. An initial course of two injections can be given from 6 weeks of age and this should be followed with annual booster vaccinations to maintain protection. In the UK there are currently different types of leptospirosis vaccine which cover for either two or four types of Leptospira bacteria.

    Although vaccinations may not completely prevent a dog from getting leptospirosis they do significantly decrease the risk. Many owners worry about vaccinations and “over-vaccinating”; however, reactions are uncommon and typically mild (decreased energy, low-grade fever, decreased appetite, local swelling) and short-lived. The benefits of vaccination far outweigh any risk for the vast majority of dogs which is why they are recommended.