A lesson in the importance of leptospirosis vaccination


As leptospirosis becomes more widespread in the US, this serious disease is striking where you least expect it

Content sponsored by Boehringer Ingelheim Animal Health

Leptospirosis is a zoonotic bacterial infection that affects both animals and humans, and it is becoming increasingly common in the US.1 The bacteria that cause leptospirosis are found in the urine of infected animals and can be transmitted to dogs and humans through contact with contaminated water, soil, or food, or through exposure to the urine of infected animals.

With an estimated 1 million cases reported worldwide each year, leptospirosis is a global One Health concern. In areas with poor sanitation and hygiene, the risk of contracting the disease is much higher. In addition, climate change and natural disasters can increase the risk of leptospirosis outbreaks, as flooding and other extreme weather events can create conditions that are favorable for the bacteria to thrive.

Leptospirosis can be a serious disease in dogs, with symptoms ranging from mild to severe. Symptoms of leptospirosis in dogs may include fever, vomiting, diarrhea, lethargy, loss of appetite, muscle pain, and jaundice. In severe cases, dogs can develop kidney and liver failure, and may experience bleeding disorders, which can be life-threatening.

Presenting at WVC 2023, Jane Sykes, BVSc (Hons), PhD, DACVIM, tackled the topic of leptospirosis and how it can appear even in the unlikliest of locations.

The 2021 Los Angeles leptospirosis outbreak

In 2021, an outbreak of leptospirosis occurred among dogs in the Los Angeles area. The outbreak was initially reported in the San Fernando Valley, and later spread to other parts of the city. Over 200 dogs were diagnosed with the disease, and 13 died as a result.3

“If dogs are getting exposed to rodents or ingesting rodents…you don't have to have these perfect environmental conditions for lepto to occur,” said Sykes. “Hence, outbreaks in regions that are more arid. These are in regions where people are not vaccinated for lepto because they're like, ‘Well, I wouldn't see lepto here; the conditions are not right for it,’ but it can certainly occur.”

Occur it did. The leptospira serovar canicola was considered the likely cause of the outbreak. As dogs are the primary reservoir for the canicola serovar, not wildlife or rats, the outbreak was likely driven by dog-to-dog transmission of the bacteria in group settings such as doggy daycare. The Los Angeles County Department of Public Health issued an alert to veterinarians and pet owners in the area, advising them to take precautions to prevent the spread of the disease. This included avoiding contact with standing water, and vaccinating dogs against leptospirosis.

The 2021 outbreak was a serious public health concern, highlighting the need for awareness, prevention, and prompt treatment of the leptospirosis.

The importance of leptospirosis vaccination

There are several leptospirosis vaccines available for dogs that are designed to protect against the most common serovars of the bacteria that cause the disease, such as Leptospira canicola, L. grippotyphosa, L. icterohaemorrhagiae, and L. pomona. The choice of vaccine depends on several factors, including the age and health of the dog, and the potential risk of exposure to the disease. It is important to note that no vaccine provides 100% protection against leptospirosis, and that vaccination does not guarantee that a dog will not become infected. However, vaccination can help to reduce the severity of the disease and improve the chances of survival in the event of infection.

More specifically, Sykes credits the jump to vaccines that protect against 4 Leptospira serovars vs 2. “We've got good evidence now coming out of the literature that supporting a reduction in disease following a change from 2-serovar vaccines to 4-serovar vaccines,” said Sykes. “Leptospirosis was still occurring in dogs vaccinated with 2-serovar vaccines, but where this change has been made in different countries around the world, there's been a decrease in leptospirosis.”


  1. 30 Day Alert Maps. Pet Disease Alerts. https://petdiseasealerts.org/alerts-map/#/. Accessed February 22, 2023.
  2. Sykes J. A shifting spirochetosis: update on leptospirosis. Presented at: WVC Annual Conference 2023; Las Vegas, Nevada. February 19-22, 2023.
  3. Leptospirosis in Dogs in Los Angeles County in 2021. Los Angeles County Department of Public Health. Accessed February 22, 2023. http://www.publichealth.lacounty.gov/vet/Leptospirosis2021.htm
© 2024 MJH Life Sciences

All rights reserved.