How do dogs contract leptospirosis and how can it be prevented?

Original Question: I read all the information on leptospirosis and I was wondering if you know how it is contracted? Ingested? Airborne? Through the skin? - Jeanne

Jun 21, 2019

Hi Jeanne,

Leptospirosis is caused by an infection with the bacteria Leptospira. There are actually several different variations, which are also known as serovars, and the presence of these really varies depending on your geographical location. Dogs are the primary host of the Leptospira bacteria, but many other mammals can be infected and it’s been shown that Leptospirosis can develop in over 150 different species and that’s only the ones that have been reported. So that includes farm animals, wild animals, rodents, and also humans, which is clearly important here. Leptospirosis is zoonotic, which means that it can be transmitted from animals to humans. Therefore, if your dog has Leptospirosis, then we really need to be careful with how we’re hospitalizing, treating and managing them at home. It also gives an added impetus to protecting them from developing that infection in the first place because that will reduce our risk of also contracting the disease.

The bacteria infect and multiply within the kidneys and are then shed in the urine, which is the main source of contamination. Dogs can become infected just by coming into contact with either the infected urine or urine-contaminated soil, water, food or bedding. The Leptospira bacteria can cross the mucous membrane such as the gums or they can be transmitted directly across the skin if there are wounds or small abrasions present, which there are very likely to be in a dog’s feet. Therefore if a dog is walking through contaminated water or soil and they have small cuts, nicks or abrasions in their skin, then there is the potential for transmission of the disease.

The bacteria doesn’t replicate outside the body so it’s not going to spread to areas where animals haven’t urinated, but the Leptospira bacteria can remain in an infectious state in the soil or in water for many months. Again, that’s going to depend a little bit on the environment and location of where you are in the world because the bacteria can be killed by freezing or by exposure to UV. So if you’re in a very cold area and it’s winter, then Leptospira aren’t going to survive and it’s going to be much less of a risk. If you live in a very sunny environment where the UV rays are constantly shining down on the soil, then that’s going to help with the breakdown deeper down in the soil but if there are shady patches then it still might potentially be a risk.

The risk of a dog contracting Leptospirosis is also going to depend on their lifestyle and the local presence of Leptospirosis. For example, dogs that drink from rivers, lakes and streams are more likely to get contaminated. Also, rural dogs that are allowed to roam, dogs that have access to sewage which depends on the sewerage system in your area, and suburban or urban dogs with an infected local urban population of wildlife such as rats, mice, fox and squirrels depending on where you are in the world.

What can we do to protect a dog that is living in a high-risk area from contracting Leptospirosis? We would want to avoid these high-risk areas if at all possible but realistically that’s very hard. Vaccination is the best option when it’s felt that there is a risk of a dog catching Leptospirosis. Like I say, we’re protecting not just the dog, but also ourselves from infection as well. Vaccination is very effective at preventing infection and it lasts for at least 12 months. Unfortunately, it’s not one of these vaccines that can be given every three years or so and it should be given every 12 months. Ultimately the risk of Leptospirosis is going to depend on where you live and I strongly recommend that you discuss vaccination options with your vet.