What is Leptospirosis?

Leptospirosis is a disease which can affect animals and humans, caused by infection with bacteria called Leptospira.

Leptospirosis can cause kidney failure and liver failure, and occasionally severe lung disease and bleeding disorders in animals. The clinical signs of leptospirosis vary considerably from no signs of infection, to just a mild illness of short duration from which the animal recovers quickly on their own, to severe disease and even death ​[1–3]​. There have been a number of outbreaks in dogs in specific areas of Australia in recent years (e.g., in the NSW Central Coast, Central and Northern beaches areas of Sydney and NSW South Coast)​ [1, 2]​. Cases of canine leptospirosis have occasionally been reported in other areas in Australia, including North Queensland, Tasmania, and Victoria ​[2]​. This can be a very serious disease; outbreaks in NSW between 2017-2022 have had very high mortality rates where over 70 %of dogs who became infected died ​[1, 2]​.

Which animals are affected?

There are different kinds of Leptospira bacteria (called serovars), which cause infection and disease in different species.

Dogs are the companion animal most at risk of developing leptospirosis. Cats can be infected but this is rarely reported and the disease is normally mild ​[4]​. Other animals can also be affected, including cattle, sheep, goats, pigs, and horses ​[1–3]​.

Leptospirosis is a zoonotic disease, which means that humans can also be affected ​[1–3]​.

The different kinds of Leptospira bacteria (called serovars) may be carried by different species. Small mammals such as rodents are the most common carriers of leptospirosis and shed the bacteria in their urine ​[2]​. Infected urine can contaminate water, soil, mud, bedding, food etc ​[1–4]​.

How are dogs infected?

Your dog is at risk of becoming infected and potentially developing leptospirosis if ​[3, 4]​:

• Their mucous membranes (i.e. lips, tongue, gums, inside of the eyelids) or any broken skin (i.e. a wound) comes into contact with infected urine or something that is contaminated by infected urine (for example, soil, water, mud, bedding, food).
• They eat tissue from an animal or carcass that is infected.
• They are bitten by an animal that is infected.
• Rarely, through breeding or if a pregnant female passes the infection through the placenta to her puppies.

Exposure to Leptospira bacteria is more of a risk if your dog ​[3, 4]​:

• is exposed to slow-moving or stagnant water (for example, drinking or swimming in waterways).
• comes into contact with rodents or wildlife (including hunting rodents or other animals), farm animals (particularly pigs or cattle), or other dogs that may be infected.
• is in an area with a warm climate and lots of rain (as Leptospira bacteria are more common in these areas)
• is in an area which has recently experienced a period of high rainfall.

What are the clinical signs of leptospirosis?

Signs of leptospirosis may include ​[1–4]​:

• Fever
• Lethargy
• Sore muscles and a reluctance to move
• Shivering
• Increased drinking
• Increased or decreased frequency or amount of urination
• Dehydration
• Vomiting
• Diarrhoea
• Jaundice (where the skin and mucous membranes become yellow in colour)
• Eye inflammation
• Difficulty breathing
• Bleeding (including blood in vomit or faeces, saliva, bleeding from the nose and small red spots on mucous membranes or pale skin from bleeding)
• Fluid accumulation causing swollen legs, distended abdomen or restricted ability to breathe

If your dog is lethargic, depressed, not eating, vomiting, feverish, has increased thirst and urination, and/or is jaundiced (yellowing of the gums and white of the eyes) it is important to take them to the veterinarian immediately.

Leptospirosis can be treated, usually with antibiotics and supportive care. The chance of recovery depends on how severely the dog is affected, and how quickly they receive appropriate veterinary treatment. If your dog is diagnosed with leptospirosis, it is recommended that you speak to your veterinarian about referral to a veterinary specialist centre as specialised veterinary care can increase your dog’s chance of survival and recovery ​[1]​.

What can be done to prevent leptospirosis?

There is a preventative vaccine available for leptospirosis ​[1, 2]​. The leptospirosis vaccination is not considered a ‘core’ vaccination (i.e. a vaccination routinely given to every dog) and, historically, in most areas of Australia it has not been routine practice to give dogs the leptospirosis vaccination as the disease has not been considered high risk ​[1, 2]​. Since there have been a number of outbreaks of leptospirosis in Australia in recent years, it is important to have a conversation with your veterinarian about the situation in your area, the risk to your dog, and if your dog should be vaccinated against leptospirosis.

Dogs who are considered at risk should have a primary vaccination course of two doses of the vaccine, given two to four weeks apart and should then have a booster vaccination yearly ​[1]​.

The Australian Veterinary Association advises that dogs who are considered at risk of leptospirosis include (but are not limited to) the following ​[1]​:

• Dogs who are living in, or travelling to, the known areas affected in Sydney, Newcastle, South Coast, and the surrounding areas
• Dogs who have contact with rats or other rodents

If you are having your dog vaccinated before going to a high risk area, or an area with an outbreak, the final vaccination must be given at least two weeks prior to traveling to allow for optimum protection ​[1]​.

You can also reduce your dog’s risk of infection by minimising your dog’s potential exposure to Leptospira bacteria ​[4]​. Avoid your dog drinking from or swimming in waterways that pose a potential risk (such as rivers, lakes, ponds, marshy areas, slow-moving or stagnant water) and minimise their contact with potentially infected animals such as farm animals and rodents, including making sure that they do not eat carcasses ​[4]​.

If your dog is diagnosed with leptospirosis, it is recommended that you seek medical advice, as this is a zoonotic disease (it can affect people) ​[1]​. If you have questions about leptospirosis in people, please consult your doctor.