Canine Leptospirosis – On the Rise?

Leptospirosis is a zoonotic disease; in both dogs and humans, leptospirosis can cause severe kidney or liver failure, meningitis, difficulty breathing, and in some cases, lead to death. The bacteria responsible for this disease, Leptospira interrogans, is typically found in warm, wet, stagnant areas such as lakes, ponds or puddles and can survive for several months in these environments. Wildlife and rodents can harbor disease and spread the bacteria when they urinate. Direct transmission from one infected individual to another is rare but exposure to bodily fluids from infected individuals is an important risk factor to contracting the disease. The exposure does not need to be direct and may occur through contact with urine-contaminated items such as water bowls, bedding, or food. In recent years, there appears to be an increase in cases of canine leptospirosis within North America. The role of the environment including number of trees, and amount of standing water or wetlands, is being investigated to better understand methods to prevent outbreaks in dogs. Another contributing factor to the prevalence of leptospirosis outbreaks is limited access to clean drinking water. Consequently, areas that are prone to flooding tend to result in a higher chance of exposure.

While there has been an overall increase in the number of cases, it is also important to note the increased danger of leptospirosis exposure following natural disasters such as floods and hurricanes. For example, in the wake of Hurricane Maria, Puerto Rico saw a spike in the number of suspected cases as clean drinking water became scarce. Additionally, the floodwaters introduced several other means by which to transmit Leptospira interrogans and other waterborne pathogens. An individual is exposed to pathogens including Leptospira when wading through contaminated bodies of water, especially if they are submerged or have open cuts or abrasions. Dogs may end up drinking flood water or other contaminated water sources. Eating food that has been in contact with contaminated water can also spread the disease to people and pets. To minimize the impact this pathogen has on public health it is important to develop the best practices to first prevent the disease, such as vaccinating your dog and preventing exposure to contaminated sources, as well as treating the disease should an infection occur.

The AKC Canine Health Foundation (CHF) is currently funding two studies that aim to increase the understanding of leptospirosis and how to better combat it. The goal of the first study (2380-A) is to identify risk factors for canine leptospirosis that lead to increased likelihood of an outbreak. Data on leptospirosis cases is being compared to environmental and socioeconomic data to identify trends in the prevalence of canine leptospirosis. This information will be compiled into maps that will allow veterinarians and pet owners to become better informed about potential outbreak locations and disease severity.

The second project (2461-A) looks at the innate immune response in dogs naturally exposed to Leptospira. Some animals may carry the bacteria yet do not show any clinical signs of disease. Comparing the role of the innate immune system between animals with and without clinical signs will provide a better understanding of the immunopathogenic mechanisms of infection. Furthermore, the data from this study may one day lead to an improved vaccine or more directed therapy for dogs.

Increasing awareness and understanding of leptospirosis is important to the health of all dogs. As part of a CHF-sponsored educational series “Current Topics in Infectious Disease”, see the latest update from Drs. Jason Stull and Michelle Evason.